- Today, I'm going to talk in this series on different routes of transmission of infection, about sexually transmitted infections. And also those are passed on intravenously or bloodborne infections. And this is part of a series looking at the broadly five routes by which we infections are passed on between people or occasionally between animals and people. And the route of transmission in all cases is really important because it's key to understanding how the disease behaves. And it's also key to understanding how we control it. And the ones I've talked about already are vector-borne diseases, diseases passed on by insects and arachnids, oral diseases passed on by food and drink. And today I'm going to talk about sexual diseases, sexually transmitted infections and bloodborne infections. Subsequently talk about respiratory and touch, which are the final ones in the group. Almost all infections have a dominant route by which they are mainly transmitted. Some of them it's exclusive. They only go by that route. Some of them have got a secondary route and that's important for some of the diseases I'll talk about today. Now this is a big contrast in terms of this route of transmission, the sexual root, from the ones I've talked about so far, the previous things I've talked about in this series can be passed on between complete strangers, often at a distance. So for example, an oral infection could be passed on up the food chain. Passed on through a watercourse, the vector-borne could be passed on by a mosquito flying from one village to another. In contrast, sexually transmitted infections, STIs are almost exclusively transmitted by close contact. The two between two people where the infecting person knows the infected person very well. And usually is very fond of them, loves them and cares deeply about them, or at least desires them. So it's a very different form of transmission. And because this is something which is essential for the survival of the species and it's something which is happening the whole time among adults, several viruses, bacteria, and parasites have evolved to take advantage of the strong human desire for intimacy, for love and for sexual contact. It's a potentially from the infection's point of view, a very efficient transmission strategy. Two people are very close together for prolonged periods, often not taking huge amounts of care because they have other things on their minds. And it's also often a relatively less defended parts of the body, immunologically, the skin for example, very tough, very few things and get through it. I'll come onto that in a later lecture, the gut which we've talked about, hugely defended by multiple layers defects, less so for sexually transmitted infections. And this can happen in all forms of sexual contact, heterosexual men having sex with men and women, having sex with women, all of these are possible, but different ratios, which I'll come on to. It's often assumed and wrongly, that SDIs are magically trivial. And some of them are, but several of the major diseases of humanity both now, and historically are transmitted mainly or exclusively via the sexual route. These include, and I'll go into these in greater detail, HIV, which is the last really serious pandemic we had before COVID and has killed over 36 million people to date. According to WHO statistics, syphilis, a major multi-system disease, again, caused huge epidemics when it first arrived, several infections that cause cancer, including a HPV, which causes cervical cancer, hepatitis B. Again, I'll go into those in greater detail and then many more classical sexually transmitted infections, which can cause significant physical problems, including infertility, particularly in women, but in both genders, stillbirth and other problems in the course of a pregnancy and neonatal damage. And they can also cause significant stress and relationship damage. So these are not trivial infections by any means. Now because the route of transmission between the two people is so short because people are basically against one another for a very significant period of time. The ability medically to intervene is very different from other routes of transmission. So if you think about the vector-borne diseases, if you can intervene with the insect that is carrying the disease between one person and the next, you can stop the transmission. If you think about the waterborne diseases, if you can keep feces out of water, if you can have proper sewage disposal, proper clean water, you can, for example, reduce or remove completely the risk of infection there can be a medical intervention between the infected person and the person who becomes infected subsequently. For sexually transmitted infections, of course you can't, the contact is direct and it is personal. So there's much greater Alliance medically on finding cases amongst people who are infected early on in their disease and treating them. And if they're in a stable partnership or have had recent sexual partners, who can be contact traced, treating their contacts at the same time. Now, one of the biggest barriers to being able to do this is embarrassment or shame, where someone feels embarrassed about the fact they have a sexually transmitted infection. And this is often the reason people don't seek help or don't seek help early enough. And I think I cannot stress too strongly that for all medical staff, nursing staff and others, diagnosing and treating SDIs is common and normal business. These are common diseases. They're things people get and they're things which can almost in all cases be treated. So stigma is a very major barrier to diagnosing and treating STIs and recognizing this, there are several different routes by which people can seek treatment. Obviously people go can go to their GPS and through those kinds of routes, there are also separately and entirely confidentially, sexually transmitted infection clinics which specialize in this area and keep completely confidential records separate from other ones. So there are various ways people can access care. Medical interventions can also include behavior change, and this is possible, but people have to engage with it. And it includes things like using condoms, which we'll come back to. Now, there are some important sexually transmitted infections for which we now have vaccines, but for most of them, the main stay of management is treatment. And that of course means you've got to diagnose it before you treat it, so unlike a vaccine, which you just give to everybody, the treatment will only be given to people who are infected, so people have got to be identified. Unsurprisingly, STIs are mainly diseases of sexually active adults. So most infectious diseases, if you think about them, have their biggest impacts in the very young and in the relatively or very old. And if you think about COVID, which we're going through at the moment, really heavy burden has fallen on older people because of the higher risk of that age. But for many infections, it's the very young and the very old who are most effected. SDIs are in a sense, the complete opposite of that. They occur if they do occur after sexual debue. And so therefore they're usually diseases of adults and specifically they're most commonly acquired early on in people's sexual lives, before they have formed their lifelong partnerships. And therefore, they tend to be heavily weighted towards a younger adults, very different age spectrum. It's important to understand though that many can be, if untreated, and many people don't know they're carrying them, they can remain infectious for years and in some cases for life. So if someone does get infected in young adulthood, they could carry that infection with them for years or decades. And people are often unaware they've got them, have no symptoms themselves. And the first time they'd realized they've acquired at some point along their sexual life, a sexually transmitted infection is when a new sexual partner develops the infection and get symptoms. And this could be many years after the last sexual relationship they had, but because the disease has stayed there and without symptoms, people just are not aware of the fact they've got it until as I say, they pass it on. Just to put a little bit of a few numbers on this, this is the rate of new STI diagnosis by gender and age. And there is a bit of a difference between the genders, in England in 2019, this is the year before obviously COVID started to change the statistics provided reasons. And what you can see is the youngest, 15 to 19 are the Boston bars. And they go right up to people in the sixties at the top, STIs can happen to any stage on the life course, but a really heavy concentration, particularly in people in the early and mid twenties and early thirties. An important part of STIs particularly to pull out I think is the impact on pregnancy and on childbirth. And it's really very important to identify STIs if someone has got them, ideally before they become pregnant. And certainly before later stages of pregnancy and labor. Some major STIs can be passed vertically from mother to baby, including HIV, syphilis, and hepatitis B, all of which I'll talk about in a bit more detail in a minute. Some of them can be passed on to the baby in the birth canal during labor. So as the baby comes out, and they can cover the baby, get on the baby or into their eyes and cause significant issues for the neonatal baby when it comes out. So therefore checking for STI, remembering that these are common and treating them before or early on in pregnancy should be seen as normal, good care. By definition, a woman who is pregnant is actually active. Now it may seem slightly odd that I put bloodborne infections alongside sexually transmitted infections. But the reason for doing that is that for the most important bloodborne infections, the ones that are primarily or largely or partially transmitted by blood to blood contact are also sexually transmitted. So they're the same infection, but by different routes. And historically, medical practice was an important way that some of these were passed on classically, for example, using the same needle to inject several different people or using an improperly cleaned or sterilized knife or scalpel in surgery, or indeed in traditional medical practice, scarification and things like that, where the same object would be used on two different people, transmitting blood from one to the second, relatively small amounts, but enough to pass on an infection. That's obviously gone right down. People now use in medical practice, almost exclusively reusable or very heavily sterilized objects. The second medical way this was transmitted, and there were some very tragic examples of this where blood products before there was effective screening. And in particular, this was important for HIV, for hepatitis B and hepatitis C. The third group, again, that's been largely eliminated by screening methods. The third group where infections are passed on blood to blood. So from one person's blood directly to the others, usually by a syringe is people who are intravenous drug users who share needles and syringes. And this used to be very common practice in many places and still is very common practice in many parts of the world. And this can pass on many major bloodborne infections, including HIV, hepatitis B and hepatitis C. There are others, but those are particularly important. And there are a variety of ways which these can be addressed. For example, using needle exchanges to encourage people always to use clean needles keep a needle at least exclusive to themselves. I think it is worth just pausing on the issue of blood transfusions and blood products. Things like factor eight, these are an extraordinary gift from one person to another they usually don't know at all. People who donate blood are extremely altruistic and the health service and people's ability to have operations and to recover from major traumas and things depend on people being altruistic. So they can be lifesaving, but if not properly managed, they can also transmit infections. And the way that blood is managed between the person who donates it and the person who receives it is it's done to minimize the chance that any infection can be passed on by this route. This includes things like saying, please don't give blood if you're unwell at this moment, if you've got an infection, if you've got fever, some travel destinations, so for example, if someone's gone to a place where there's malaria, malaria can be passed on blood to blood, mainly passed, almost entirely passed on via mosquitoes, but can be passed on by blood transfusions, very rarely, but the important blood infections, which can be passed on without careful management include HIV, hepatitis B and C. And these have to be screened for, people obviously are excluded if they know they've got disease, but they also have to be screened for afterwards. And the infection rate by this route is now very low indeed. Now I'd like to move on to some of the important infections that are worth thinking through, and really mainly concentrating on the sexually transmitted infections. And the first of these I'd like to talk about is syphilis. Syphilis was a new disease in Europe, or we think it was probably a new disease in Europe in the 1490s, lots of different views about where it came from. Did it come over with Columbus or so on? What certainly happened is it got spread following the Siege of Naples. And it's spread over a very small number of years in the 1490s and swept through Europe over a small number of years. Probably it was more severe early in its waves then subsequently, but it was and indeed still remains a serious disease. It was really realized fairly early on in this new epidemic, this frightening epidemic that spread through Europe, that it was sexually transmitted and as has happened very often, this was therefore very quickly blamed on foreigners, in England and UK more widely, it was known as the French disease elsewhere in Europe it's known as the Italian or Spanish disease, Russia, it was known as the Polish disease and so on, but I think there's a theme emerging here, but it was actually a disease that was passed on in every country in the continent. As a disease which was both dangerous, caused serious illness, also caused the visible scars that people you could see very often who'd had syphilis or been treated for it due to some of the scarring it caused. And the stigma that went with it, particularly associated with the fact that it was sexually transmitted initially, and the feeling that this was associated, with kind of moral laxness, it was very widely feared and it had a very profound effect on the practice of medicine. Now, syphilis, although passed on sexually, is a disease of the whole body. Primary, it starts off with a shanker, which is a ulcer that's usually painless lasting three to six weeks. Trivial of no great importance. Normally in the genitals can be slightly different forms in the throat or perianally. Secondary syphilis then follows after that and causes a fever and a generalized rash, various ulcers, people feeling fairly unwell. And then for most people that passes, although initially, here that was really pretty serious for many people, particularly in the first wave. And then you end up with tertiary syphilis, which can occur 10 to 30 years later. And this can cause really serious problems throughout the body. And syphilis was known as the great mimic and cause problems in the brain with the nerves, with the eye, and this included something called general paresis insane, GPI. And this was something which caused both mental and dementia problems. And dementia was a very significant long-term of syphilis. And for example, something called tabes doraslis, really painful shooting pain in the limbs caused problems in the bones, in the joints, multiple kinds of things on the skins, lots of different kinds of skin rashes also can cause inflammation of the heart and swelling and inflammation of the great blood vessels and of the liver. So this was a multi-system disease and extremely dangerous over many years, taking different forms at different stages of life. And on the right I've illustrated this with what is probably the first known illustration of this treatment being treated in 1498. Now the initial treatment came from a variety of different sources, included herbal treatments, which were traditional in Europe at the stage, mercury, partly 'cause it was thought to look slightly like leprosy, which was treated this way and various woods and other exotic herbs, for example, Garcon, which came from a wood particularly imported from Latin America initially. As a new disease, it wasn't fully described or wasn't described at all actually in the ancient texts. And I think it's important to remember back to this period, much of traditional medicine was about reading the ancient texts, particularly the Greek texts of Socrates and Galen and others, and using their approach to medicine. And there was a real medical conservatism that meant that people were not wishing to move away from that very traditional form of medical practice. As a new disease, this allowed for a complete rethink of medicine and some of the more radical thinkers in medicine at that point said that syphilis had still got so entwined with all the other diseases that it led to a need for a complete rethink of medical theory and practice. And it, for example, made chemical drugs, which had been much less respectable, things like sulfur and mercury, semi respectable, led to a new, several new branches of medicine. It allowed surgeons to start to practice much more widely than they previously had because used pastes and oils, rather than just internal drugs, which were the preserve of other medical practitioners, positions, led to quite a lot of building or conversion of new medical establishments. Some of the old leprosy hospitals were turned into syphilis hospitals from Lazarre houses to Locke hospitals, wards are built, for example, just up the road from here, the Daughter ward at St Bartholomew's. And it had a very substantial effect on society where it probably changed quite a lot of behaviors. And on literature, you won't get through many, or you certainly won't get too many restoration comedies in many Shakespeare plays without some indirect reference to it. And it remained a really very serious disease, both in numbers, as well as in its medical impact right up to the antibiotic era. And if you go down to about 1919, a Royal commission assessed that around 10% of the adult male population of London had it at that stage. In the US army, it was the second most common of illness leading to loss of duty, only exceeded by the great flu pandemic, massive pandemic of 1819. It was one of the communist causes dementia if you went back 120 years, and what changed that where the introduction of the first really good antibacterial drugs, first of all, moderately effective and relatively more dangerous arsenic-based drug, Salvarsan, which was introduced in 1910. And the thing which really transformed it was the was penicillin, which remains a mainstay of treatment of syphilis to this day, largely collapsed the epidemic in high-income countries. And if people were treated potentially for other infections, which they might not even know they had syphilis, between the initial infection and their late complications, it could prevent those late complications, but to get rid of this as a major public health problem, there was also a need, and this was set up, to have a whole medical service associated with finding people with cases and then finding their contacts and treating all of them. And this really led to a significant transformation of this major sexually transmitted infection. Now, the way in which cases were calculated was varied over time. But as you can see, there was a really substantial numbers of cases of syphilis diagnosed in England, up until the 1950s. And then those numbers really collapsed. And this is the impact of penicillin, a little bit of a rise subsequent to that. Then a fall away probably driven by changes in sexual behavior around the existence of HIV. And more recently, a bit of a comeback, particularly in England, in men who have sex with men, but not exclusively. So that's syphilis, a really major disease, historically, even more important, but still non-trivial. Then we move on to HIV, AIDS and between the 1980s and the 2020s, HIV AIDS has been one of the most severe new threats to health in the lifetime of most people who are watching this program. Over 36 million people have died to date, more will do so, and this has been a problem worldwide. So this is the last really a remarkably bad pandemic before we reached COVID particularly true in Africa, but all around the world, including here in the UK and the photo on the right is from a book about a ward I actually used to work on early in my career. The early years of HIV are still being researched, but what is clear is that this jumped species, and it was originally one of the family of, or more than one of the family of Simian viruses, SIV. And it crossed several times between monkeys, probably among hunters, probably blood to blood actually, to humans, leading to HIV, which was probably started in what was then, now DRC from chimpanzees and separately, HIV2, a slightly different version of it in west Africa. And probably these were circulating in humans from the 1920s, certainly before it was first picked up. It was first identified in the 1980s and the 1981, gay men in California developed a very rare lung disease, something called PCP, not normally seen otherwise in young men or young people, in New York, there was a whole cluster of people who had again, a kind of cancer, which is extremely rare in the general population called Kaposi's sarcoma. Other groups were found around intravenous drug users in the USA and simultaneously or near simultaneously, cases started to be described of what's called slim disease and a variety of other forms in Uganda, and then elsewhere in Africa. So early 1980s, lots of people were diagnosed and they were being diagnosed not with HIV, which at that point had not been identified, but with AIDS, a very serious disease, which at that point was for practical purposes, 100% fatal. Now HIV, which is transmitted sexually in the main, it destroys key parts of the immune system, particularly the bits that are mediated by what's called the CD4 cells, but it takes many years to do that. And on the right here, what we have is the kind of schematic in red is the cell count where high is good and low is bad. And in the blue we have the virus. And what you initially have is a little bit of a dip, but then the immune system recovers for a number of years, usually eight or more in most people. And then it begins to deteriorate over time. And as it deteriorates, people begin to get more and more infections and when they happen, they are much more dangerous than they would have been in people who had an intact immune system. So the immune system, this key part of the immune system is essentially gradually eroded to almost nothing. Things like TB, pneumococcal pneumonia. Some salmonella's, various forms of meningitis, including fungal ones, several fungal infections of the lungs, of the brain in particular, the body more generally. And also because the immune system scans the body for cancer and helps to destroy cancers, several cancers or cancers driven by infections, such as Kaposi's sarcoma. So not having CD4 cells and the immune system that goes with them leads to multiple, very serious diseases. And this is what some combinations of these is what constituted the group of syndromes caused AIDS. Once this has started to circulate around the world in this pandemic, several different independent essentially epidemics that overlapped occurred, which all of which led to HIV AIDS. There was a largely heterosexually driven sexually transmitted infection epidemic, particularly in Africa and especially Southern Africa, parts of Asia, parts of Latin America, but also Europe. This was by far the largest. So the greatest majority in terms of numbers was this large global heterosexual STI epidemic. And there were many children born to mothers who got HIV. So there was also a subsidiary epidemic in children who died young. Then there was simultaneously, a significant epidemic in men who had sex with men, particularly in Europe and north America, but also globally. And there's obviously overlap between these two. There was an epidemic amongst people who were intravenous drug users, because HIV, in addition to being a sexually transmitted infection is by far its predominant means of transmission, also a blood to blood transmitted infection. And tragically, in addition to these other multiple other tragedies, there was some blood products such as hemophilia suffers where it got into the supply. So this led to large numbers of people being infected. And initially, everybody who was infected went on to die. The spread of this was really quite rapid. And these maps show the spread from top left to bottom right over from the mid eighties through to the end of the 1990s. Really over this entire period in Africa, the most effected continent, although as I say, it's in every continent, it was really substantial. And over this period, there was for practical purposes, 100% mortality and the numbers infected were dramatic. Certainly at the point I was a doctor in Southern Africa. Malawi at that stage, there was a situation where in many parts of Southern Africa, up to 30 or even 40% of people, of young adults were infected, sample studies where I was around 30% of pregnant women in some studies had this, all of them would go on to die. So if you think about the impact of that on society, it was very, very profound. In the absence of medical countermeasures, drugs and vaccines, the initial response had to rely almost entirely on trying to change social behavior. Was of course of the net sexually transmitted infection, you don't have that ability to intervene except by changing behavior. And some of these posters are some of the ways in which people tried to change overall behaviors. Some, I would say more likely to be successful than others. And it was also important, as well as trying to change behaviors that led to people reducing their risk, having fewer partners, for example, and taking precautions, also to try and encourage people to understand that they could not catch this sexually transmitted infection from ordinary social contact. There was a real fear that you might pick it up if you shared a workspace or a friendship group with someone with HIV. And of course that wasn't true, unless you actually were having a sexual relationship with them. Probably the most important early initiative was the promotion of condoms and other barrier methods of contraception. And just like to make a few points about this, there was really no very good evidence that abstinence only campaigns had a major impact on HIV. That doesn't mean that it didn't in individual cases, but in terms of slowing the epidemic down, on the flip side, there was no good evidence that condom promotion in any way increased sexual activity, no one was likely to have sexual behavior because they had a condom promoted to them, if they weren't intending to in the first place and promoting condoms, and for some people filming female condoms and diaphragms reduced significantly the risk of HIV and importantly, other sexually transmitted infections. But importantly also not to zero. An additional behavior which was found to be important slightly later in the epidemic with circumcision, which also reduces the risk of HIV transmission. But the really big transformation occurred with the advent of drugs to treat this terrible, entirely fatal, new disease. We got no vaccine for HIV yet that's available in widespread use. Obviously it is still being looked for, but since the 1980s, many very effective drugs have been introduced. The highly effective antiretrovirals, sometimes known as HAART. And they were really available from the mid 1990s. Initially they were moderately effective, had significant side effects, very expensive, complex to deal with, lots of drug resistance, but there have been steady improvements over time. And medicine always tends to advance, not by sudden breakthroughs, but by incremental improvements, one on top of another. And this poster, I think rather well illustrates how HIV is often moved from a situation where people had to take many drugs every day to single drugs and even most recently to injections, they may be able to take for prolonged periods of time. So steadily improvement and the price dropped a lot. And for a variety of reasons, some of which were to do with important legal challenges, they became available to lower-income countries. Where in fact, the great majority of people who had HIV were living. As a result of these drugs, the life expectancy of HIV infected people who are diagnosed early and treated is basically the same as the non-infected, but it is important that people are diagnosed early. And cannot say this too often, early diagnosis is the key to managing potentially sexually transmitted infections. So the introduction of these drugs and then their spread worldwide has led to a really major reduction in deaths. And what this chart shows is deaths by age. And those in red are people 15 to 49. So HIV was a disease, still is a disease that predominantly kills people in their young adulthood. And the introduction of the antiretrovirals has really brought that down and in the countries where there are widespread antiretrovirals and have been for many years, down to very close to nil, will never be completely nil. it's also was found, and again, this took a little while to be proved, although it was theorized from fairly early on, that if you treat people effectively, that reduces the chance that they will pass on the disease and the chance of someone with HIV who is well controlled and antiretrovirals, passing on HIV to a partner is close to for practical purposes, nil. So highly effective. So if people are in stable relationships where one person's got HIV and the other has not, if the person with HIV is well controlled, the risks to the other person are absolutely minimal from that relationship at least. Additionally for people, we now also have some people will use pre-exposure prophylaxis, where they take antiretroviral drugs if they're going to have high risk sexual encounters with someone they're not in a stable relationship with in particular, and this reduces transmission by up to 99%. So these are drugs being used to reduce transmission in either direction. Despite that, the impact of HIV on societies has been massive. This is a schematic, a relatively old one, but I think it rather powerfully illustrates what kinds of impacts are likely to have happened. In the light blue bars is the age structure the would've been in Botswana, one of the most heavily affected countries in the world, and in the dark blue is what the age structure was as a result of this pandemic. And what you can see is that the impact was really very profound. And if you think about what happens when you remove such large proportions of young adults, of working age, parents and also of children, the impacts were obviously tragic and extraordinarily widespread. There was also a significant epidemic in children and in the early HIV epidemic, between 50 and 45% of all children to HIV positive women were infected. And of course the women themselves would go on to die. And usually if they had HIV, their partner would have HIV. So the children who were not infected were left as orphans. So it effected people in multiple ways. Most of those were infected actually in the birthing process or during pregnancy, but pregnancy and breastfeeding were also important. So you could pass it on various stages in the early life, but particularly in the birthing process, as a result of using highly effective drugs, this is now less than 1%. Really this has dropped away, in the UK, less than 0.5% transmission. The key thing being to identify it in pregnancy and treat it, and if necessary, take additional precautions around the birth. HIV though remains a major global threat, and this is broadly the map of the prevalence of HIV. How many people have it now, down to where it was, but still a very significant global problem and with HIV in every continent. But there have been quite significant shifts within that pattern. And this is just showing where HIV prevalences, and then the change over the period between 2000, 2017. And you can see some areas, for example in Africa, the rates have gone right down in green and some areas indeed, they've gone up. And this has to do with local practices and particularly how much treatment is available and early diagnosis. In high-income countries, HIV cases are now largely dropping because people are identified early and put on effective treatment, which means they're not likely to transmit, and deaths are very rare. So in the UK, life expectancy for people with HIV, who are identified early is for practical purposes the same as for anyone else. And the rates of transmission are reducing because of this effective treatment in all the different routes, by which this is transmitted. Men who have sex with men heterosexually and others. So that's the two really major, systemic diseases, sexually transmitted. Now I'd like to move on to an important disease, which causes cancer and that's a human papilloma virus, HPV, this is exceptionally common and it's true. It's sexually transmitted at an early age. So young women tend to get it very early in their sexual lives very often. Now human papilloma virus, there are a lot of them, some of them are largely so trivial that you don't get anything with them. Some of them cause warts, which are not aesthetic and can cause a lot of psychological and sometimes relationship distress, but they're not dangerous, but there are some of them, in particular, HPV 16 and 18, but there are others which cause cancers. And in particular, they tend to cause cervical cancer in women. Globally around half a million people are affected. And around 3000 cases a year here in the UK, and to put a kind of ratio on it, roughly one in 140 UK females will be diagnosed with cervical cancer in their lifetime at the moment. But for reasons I'll come on to, this will change. Often, they will get their cancer early in life. So this is the age distribution on the right of this cancer. And because it's driven by sexually transmitted infection like the other STIs, it's predominant in young adults, very different from most cancers which are in much older age, it should by now really be almost 100% preventable by a combination of vaccination and screening, particularly in the young cohorts coming through now. And the reason for that is that screening has been really important and will remain important. But the thing which is really going to get on top of this is vaccination. The vaccination for girls in the UK against HPV 16 and 18, which are the key ones which drive most of the UK cervical cancer was introduced in 2008. And since that time, these particular HPVs the prevalence of them in the young female, adult female population has really dropped away very substantially. And the vaccine effectiveness of these is over 80%, not 100, but certainly over 80%. And what these graphs show is that some of the key HPVs that drive cancer have decreased, but the ones which actually were irrelevant to cancer stay the same. So it's not a change in sexual behavior. It's because people are vaccinated. And what we know as of just this last few months, this paper was published very recently in the Lancette. We now know that this is leading to a substantial reduction in cervical cancer risk in England. So very large study to over 13 million years of followup in people younger than age 30. And these are the cohorts. And in those who were in the youngest age when they were vaccinated, 12 to 13 years old, 87% reduction, slightly older age, 14 to 16, still a substantial reduction, very substantial reduction, 62% society lower, once you get up to 16 to 18, 34% reduction, what this shows is that it's still worth doing, but actually this is a virus which people tend to acquire extraordinarily early, in many cases. So HPV vaccine really important, and this is over time, going to lead to a massive fall away in this important cancer of young women. And these vaccines are improving. So the number of HPVs they're up against is getting wider. That will have a bigger effect on some of the rarer HPVs causing cancer. The safety data is getting stronger and stronger. These are very safe datas, vaccines. There's been an extension of the vaccine to boys. This helps both boys who later become men who have sex with men, but also will help to accelerate the reduction in women, so it's got some big pluses. And in addition to cervical cancer, HPV, sexually transmitted can lead to vulva, penile, anal cancers and some mouse and throat cancers. So the vaccines will help against all of these. And additionally, the new vaccines are also protective against genital warts, which cause as I say, a lot of people distress. So multiple reasons to want people to get vaccinated at as early in age as possible. The other two infections, which are particularly associated with the cancers that are passed on sexually and bloodborne, and in both cases, it's a bit of both, are liver cancer due to hepatitis B and hepatitis C. In many developing countries, up to 90% of liver cancer, also known as hepatoma and up to 40% in some developed countries is due to one or both of these two viruses. And in some countries, hepatoma is the most common cancer that's there. Very high mortality, once someone gets a cancer, this is a scan of someone with a cancer in the liver. Once they get it, the mortality particularly in lower income settings is extremely high. Hepatitis B is both bloodborne and sexual. It's very common actually, easy to catch. So it's easier to actually catch hepatitis B in reality than it is for example HIV. WHO estimate that about 250 million people worldwide are infected with this and the routes of transmission interact with one another. But there are a combination of sexual and blood to blood. In adults, it's sexually transmitted between men and women, men and men, women and women in theory, but men and men, men and women. Intravenous drug use is a secondary important transmission route between adults and in the UK, it's certainly an important part of the epidemiology. Then in many parts of the world, particularly where it's not being treated, there's vertical transmission, mother to child. So a mother has hepatitis B, she then transmits it to our child and then the child has it. And then there's horizontal transmission between children by just scrapping around and blood to blood contact in ordinary play. Most children will then get it before the age of five. So that is the multiple routes by which by combination of blood and sexual transmission, hepatitis B has become so common. There are some drugs to suppress it, but there's certainly no drug currently that is a cure. However, we do have highly effective vaccines for this. And we know from quite early vaccine programs that hepatitis B can largely be got rid of by hepatitis B vaccination. And this leads in due course after a number of years, to reduction in hepato cellular carcinoma. So it's significantly reduced cancer incidents and mortality first in Taiwan, where it was studied fairly early on, but now it's being rolled out in most countries in the world, including the UK, usually as in a combination vaccine with a number of other really serious diseases. I provide somewhere between 95% and 100% hepatitis B protection. The result of this is going to be a very significant reduction in this cancer, which is passed on by combination of sexual and bloodborne routes. Hepatitis C is more bloodborne than sexual. The great majority now is acquired in adults, originally, historically by unsafe medical practice, including blood, but now very much by intravenous drug use, but there's also some sexual spread as well. Although that's a lower risk in this case, different from hepatitis B. Smaller number, but still a very significant problem, no vaccine for hepatitis C, but in the last 10 years, we have got now due to scientific work, several highly effective oral drugs, which lead to up to 90% cure rate. So in sense, the opposite way round to hepatitis B and more like HIV. In fact, you can in fact cure people, which is different from the situation you find with HIV. So two important blood and sexual infections driving cancer, for which we have medical countermeasures. Switching onto the classical kind of sexually transmitted infections. I just liked to go through some of the more common ones, because these are things which are very common in society. Start off with gonorrhea, much less serious than HIV or untreated syphilis, but very unpleasant, people describe it like being peeing with razorblades in people who've got symptoms and sometimes can be serious. That can cause joint problems of variety of other problems. It's particularly a problem if people have gonorrhea in pregnancy, it's quite common, there are about 35,000 cases a year in the UK. It's the second most commonly reported sexually transmitted infection. And I think two things just to highlight with it, the first of which is it is very concentrated where you find it. This is a map of the UK 2012 and 2017, just showing the progression. It is growing at the moment, but very highly concentrated in London. And indeed very close to where I'm giving this lecture today. So it's particularly in urban settings, but the other really big problem we have with it is that there are now highly multi-drug resistant forms of gonorrhea, which ordinary antibiotic classical treatment for gonorrhea does not work for. And we are in fact, potentially going to have to develop new antibiotics for this problem. So there is a significant issue. It's getting bigger as in terms of the numbers of cases, and it's getting more drug resistant, important to highlight the complications. If people still have gonorrhea at the point they are in pregnancy, at both the fore end and during, if women have gonorrhea, they can get pelvic inflammatory disease. And this can reduce fertility. In pregnancy, it can cause a preventable miscarriage could have been prevented by treatment and can lead to premature labor. And if children are born, when a woman is infected, they can get infections in particular and dangerously of their eyes. So almost a third of babies born to infected mothers will get this potentially blinding complication that needs to be treated very rapidly, that you can see on the right. As I showed on the maps, the gonorrhea diagnoses are increasing in both men and women, both heterosexual and men who have sex with men, but particularly men who have sex with men. And it's been increasing over the last several years, arguably because people are taking fewer precautions as HIV has become less of a risk. Another disease, which got quite a lot of similarities symptomatically though it's very different disease in terms of the biology is chlamydia. It's a very common bacterial sexually transmitted infection, it's treatable again with antibiotics. Again, importantly, you got to treat both partners at the same time. Over 70% of people who've got chlamydia notice no symptoms at all. And this means they might have two or more sexual relationships between the time they get infected. And the time they actually meet someone who then goes on to have symptoms, they may be totally unaware of the fact they have it over many years. And those do have symptoms tend to notice pain on urination, pain having sex or bleeding after it, bleeding between periods and lower abdominal pain. And any of these can be pretty classical for chlamydia. Age tends to be younger adults. And it's more commonly diagnosed in men and women, but that's probably largely to do is the number of people who are symptomatic and seek a treatment. It is like gonorrhea, important to identify and treat chlamydia in women. And it can again, cause pelvic inflammatory disease and therefore have issues with infertility or ectopic pregnancies. And again, if infected in childbirth, they can cause problems in the eyes of the baby or pneumonia.'Cause chlamydia. is one of the causes of an atypical form of pneumonia. Men can cause inflammation particularly around the testes and can affect fertility, though, to a lesser extent. And men also, and much smaller number of women. Men also can get a very unpleasant arthritis for weeks to months after the infection. This is an immune response really, and that can also cause them significant disability. So it's not a trivial disease in those people who do get symptoms. And the third in this kind of group of diseases that have got some similarities is a parasitic disease trichomonas, on the right here. Again, very common, treatable, is a parasitic sexually transmitted infection. Again, only about 30% of people who have it have symptoms. And those are do it's itching, inflammation, discharge, and pain on having sex. It can cause preterm birth in infected pregnant women and like some of the others,'cause of the fact that someone's got an inflamed genital area, it increases the risk of HIV is being spread, relatively easy to treat once it has been diagnosed. So with all of these screening for them, if people have had higher risk on new sexual contact, even if they don't have symptoms'cause remembering a lot people don't have symptoms and taking any symptoms, however trivial seriously, because these are easy to treat and important if untreated. Finally in this group of more classical sexually transmitted infections, one which presents rather differently from the last three herpes. There are two main forms of herpes, simplex, herpes simplex virus one, which is the cause of oral cold sores. It's not generally sexually transmitted although it can be, can be transmitted orally to genitally. But most people just have it on the lips. It's extremely common, and as anyone who's got it. And a lot of people who are watching this will have had colddsores of the lips. What you find is you have these, these sort of bumbly eruptions that occur on the lip, usually in the same place and it breaks down to an ulcer and then it goes away because it's hiding in the nerves and then it comes back, particularly if there's trauma or a variety of other things, people tend to acquire it in childhood and then they'll have it lifelong. HSV two, which is the much more common sexual form, is very similar, but it's in the genitals. Estimated that there's just short of 500 million people have it worldwide. The UK has got significant rates although lower than the USA, where a lot of the research has been done on it. It's really similar to the cold sore in that you get an initial lesion, then it gets better and then it can come back again multiple times during life. The first time someone gets it, the primary infection can be very painful, but often people have no symptoms or just have an itching and painful ulcer which people really don't think a huge amount about, but then it can recur through life, sometimes with no symptoms at all. But with when it does recur, someone is spreading the virus potentially infecting any partner, sexual partner they have at that stage. And that's important because there's no cure for this. And currently no vaccine, although drugs can reduce both the frequency and the severity. And actually one of the biggest impacts that this infection can have is on relationships because once someone's infected often in early life, they know that there is a reasonably high chance they may infect any subsequent sexual partner,'cause it's not going to go away. Can't treat it like the previous ones and it can come back largely an known or unprovoked and infect a subsequent partner. So it is something which can have really quite important impacts on people's romantic, emotional, sexual lives. And cause relationship concerns. Finally a slightly different one. And they have not gone through all the sexually transmitted infections. There are quite a few others, but one that is not in the genitals themselves, but around them, pubic lice, also known as crabs for reasons that are really fairly obvious if you look at them under a microscope as in this case. They're not dangerous, they don't spread any diseases. They just cause some itching. Particularly if people are allergic to louse saliva, and they've evolved to live in pubic hair, that's naturally where they live. They can occasionally live on other areas with sparse thicker hair on the body, occasionally eyebrows, but not scalp hair. So head lice, knits and so on are completely different. And if you can see head lice, they're not sexually transmitted, it's not going to happen. You know, it doesn't go in either direction. They spread person to person, and of course, unlike many of the other sexually transmitted infections, condoms are not going to stop them'cause they're not actually on the genitals, they're in the hair around it. They're only able to live for a very short time off humans. So they tend to be human to human. And they're extremely easy to treat once diagnosed. If you get itching, just think about it. Treatments are really very straightforward. Finally before I just run down on some of the epidemiology, just worth noting that many important diseases have a rare, but sometimes important additional sexual spread in addition to their main route of transmission. And I'll give two recent examples, Ebola and Zika. And what with both of these we have is a very prolonged persistence of the virus for months, in some cases in the male reproductive tract and the seminal fluid that comes from that from Ebola, which is a disease of touch. I'll come onto that later, and Zika, which is a vector-borne disease, which I talked about in the first lecture in this series. And this can stay in the male genital tract for months after the man has recovered fully. And if you test their blood, the virus has gone away completely and they allow the infection therefore, to be reintroduced into a society. If the epidemic has gone away, they can reintroduce the epidemic long after initial infection, and indeed over some space, you could have a situation where someone, for example, picked up Zika in Brazil, but infected their female partner some weeks later in the USA, so it's a mechanism by which, even though it's a rare transmission route for this particular virus, something can be transmitted over time.'Cause it's over many months rather than they were just a few days and over space. Finally, just a little bit on the epidemiology of sexually transmitted diseases in the UK, they are highly clustered in urban areas, particularly in the UK, in London, but also in the other big urban areas and particularly unsurprisingly in areas where there are large numbers of young adults, areas of higher education, early work and so on. Big innovations tend to be where young adults live that therefore tends to be where sexually transmitted infections live. And what you see on the left here is a graph where all the things colored red in terms of the proportion of people infected. All of those are in London. You can see a really heavy concentration of STIs in London. In terms of what's happening over time. Some are good at going away, in particular, hepatitis B and anything associated with HPV, importantly, cervical cancer, but increasingly warts. And what you can see these green lines in men on the left and women on the right, is the green line's going down. And they will continue to go down because of vaccination programs. Some are on the other hand going up and an important one on these is gonorrhea, which is increasing particularly in men, and some are relatively low, but increasing slightly including syphilis. So over time there are changes in the epidemiology of STIs. Really it's the ones with which we have got vaccination or treatment where the rates are going down. The ones that depend on behaviors less so. So in summary, when we consider sexually transmitted and bloodborne infections, some of them are very common. Some of them are life-threatening. Early diagnosis and treatment is essential for all of them, whether serious or generally more trivial, but could be for example, a risk to fertility or pregnancy. It's really important to de-stigmatize these. And just talk about them in an ordinary way. These are just an infection that is passed on by route of infection, which is sexual. HIV, syphilis and hepatitis C have been transformed by treatment. The medical science on this has been absolutely transformational. And in the case of HPV, cervical cancer and hepatitis B, we've got vaccines, which will have a very major impact on those cancers over time. So there are some really good forward movements for these really serious sexually transmitted infections and looking, turning to the blood born ones, safe blood products, much safer medical practice means that side of transmission has really almost entirely gone away, at least in higher and middle income countries and initiatives such as needle exchanges can be important for those who are people who use intravenous drugs recreationally. Many things getting better, but sexually transmitted infections will always be with us. Thank you very much.