nm0239: yesterday i started by talking or i finished i should say by talking to 
you about the different classification schemes that are available clinical 
classification schemes that are available for AIDS diagnosis and for monitoring 
the progression in the disease and you remember i said to you that there were 
two schemes there was one developed by the Centre for Disease Control in 
Atlanta and then there was a second scheme developed by the Walter Reed 
Hospital in Washington the atla-, the the C-D-C scheme was based primarily on 
clinical observation so it was not terribly laboratory based whereas the Walter 
Reed scheme was more based on measuring clinic-, you know measuring clinical 
parameters in the laboratory over the years since these two schemes came 
available it's the C-D-C scheme that has gained common usage and you remember 
that it's divided into four stages one through four 
and that i finished yesterday by talking about stage one which is the acute or 
primary infection stage and i said to you that during this period that people 
were seroconverting they were they'd been infected they were seroconverting the 
important thing to remember about this stage is there is a large viremia and so 
that at this stage the people are probably at greatest er chance of passing on 
the infections to others but in fact in the majority of cases they will not 
themselves at that point know that they are actually infected so the point at 
which they constitute the greatest risk to society in terms of passing on the 
infection they are probably completely unaware that they are infected 
themselves okay stage one is of course followed by stage two stage two is the 
asymptomatic infection phase so that's the phase along here in terms of time 
and whereas stage one is measured in terms of weeks so really anything up to 
about sixteen to twenty weeks that sort of period stage two is measured in 
years and its its length is unpredictable okay so it's difficult to predict how 
long stage two is going to be for an individual the key thing about stage two 
is during stage two although the people are infected they are well they are ge-,
in general terms healthy now clearly if you are someone that who is infected 
the thing that you want to know more than anything else is how long am i going 
to be in stage two if you're going to be in stage two for thirty years you're 
probably not going to worry too much about being infected 'cause you're 
probably going to die of something else before you come down with AIDS but if 
someone 
says to you well you're likely to be in stage two for about two-and-a-half 
years given that you've almost certainly been infected in mid-adult life in the 
in the period twenty to forty then if somebody tells you that you're going to 
come down with AIDS in two-and-a-half years that's clearly much more profound 
effect on your life than if they'd said to you you were going to come down in a-
, with AIDS in in thirty years so clearly one of the things that that people 
have looked for in trying to study this infection is prognostic indicators of 
the length of period of stage two so are there any indicators are there any 
clinical indicators of the infection that allow you to predict for an 
individual how long they are likely to be in stage two well what can we say 
about the length of stage two i've said it's in years what do we know about the 
numbers well in the early days there was a study done of 
six-thousand-seven-hundred homosexual and bisexual men in the United States 
over a period of eighty-eight months now that's about seven-and-a-half years 
these people were all infected they were all H-I-V positive at the point when 
they were taken into the study and in that seven-and-a-half years thirty-six 
per cent of them had developed AIDS forty-four per cent of them had developed a 
condition called ARC ARC stands for AIDS related complex and ARC is a series of 
opportunistic infections it's not full-blown AIDS but it's it's a it's what 
happens at the end of the asymptomatic period when people are starting to go 
into AIDS so forty-four per cent of them were in ARC twenty per cent of them 
were asymptomatic so twenty per cent of them after seven-and-a-half years were 
still completely well c-, still in stage two what about prognostic indicators 
well one of the best prognostic indicators still is the level of your C-D-four 
count you will all remember i hope that T-cells in 
the blood can be divided into a number of subsets depending upon the antigens 
being expressed on their outer surface the two major divisions of T-cells are 
into C-D-four-positive cells and C-D-eight- positive cells the C-D-eight 
positive cells are the so-called cytotoxic T-lymphocytes so those are the 
affector cells of the cell mediated immune response whereas the C-D-four cells 
are predominantly the T-helper cells and it's C-D-four cells that H-I-V targets 
predominantly C-D-four cells that H-I-V will infect that's not solely the case 
but that's the predominant population of cells that H-I-V infects and what you 
can show is that if you have a C-D-four count of less than two-hundred per ml 
then in a twenty month period in a study over 
a twenty month period with where people were entering the study with less than 
two-hundred C-D-four positive cells per ml in their bloodstream sixty per cent 
of them at the end of the twenty month period sixty per cent of them had AIDS 
whereas for those with greater than two-hundred C-D-four cells per ml only ten 
per cent of them were in AIDS so you can see that is a fairly good prognostic 
indicator if the if you measure the level of C-D-four cells in the bloodstream 
and you find that it's greater than two-hundred per ml then you have a 
relatively low chance of proceeding to AIDS in the next two-and-a-half years 
twenty months two-and-a-b er er under two years next two years just under two 
years whereas if your C-D-four count in the blood is less than two-hundred then 
you have a significantly higher chance of progressing to AIDS in the next 
twenty-odd months 
there is one slight complication in this measurement and that is that C-D-four 
cells undergo a diurnal rhythm that is to say they're there's a 
nm0239: if you measure them at different times of the day you get different 
numbers so you have to measure them at a specific time in the day because 
there's a natural biorhythm of C-D-four level cells in the bloodstream what 
about other indicators of progression out of asymptomatic phase into er into 
AIDS well you can look at the proliferative response induced by general 
antigens you will all have had the Mantoux test for T-B where some antigens are 
spotted on your skin and you you come up in blebs as a proliferative response 
to those antigens whether you've got an immune response to those antigens well 
you can take general antigens like that and you can test people who are H-I-V 
positive and ask how good is their response to such general antigens if they 
give a poor response to general antigens that's a bad sign okay if they 
have decr-, decreased natural killer cell activity that's also a bad sign other 
factors that seem to affect progression out of the asymptomatic stage two into 
the later stages well other infectious agents there is some suggestion that if 
you are infected for example with treponema syphilis if you have syphilis 
remember H-I-V is predominantly a sexually transmitted disease globally as 
you'll see in a minute when i come on to the global figures and a coinfection 
with other sexually transmitted diseases seems to be bad news there is a 
suggestion although it's never been quantified that there may be a genetic 
component to susceptibility to to progression into AIDS now that's probably 
almost certainly got to do with the quality of your immune response how good is 
the immune response that you start out with the better it is the better your 
chance of remaining for a longer period in the asymptomatic phase when you come 
out of the asymptomatic phase into 
stage three stage three is sometimes associated with this AIDS related complex 
stage four is full-blown AIDS now in the last few years stage stages three and 
four have tended to be conflated together because once people start to show ARC 
they relatively rapidly progress into into AIDS now what are the symptoms of 
stage four what sort of things do you do you suffer from in stage four well 
there's a variety of symptoms chronic fevers night sweats diarrhoea dramatic 
weight loss herpes zoster shingles oral thrush er athlete's foot a whole series 
of opportunistic infections that normally your immune system would deal with 
relatively straightforwardly become major problems for you quite often for 
example AIDS sufferers have athlete's foot that comes up to the knee okay it's 
a very unpleasant disease once you get into full-blown AIDS what is the in 
order to be categorized as in 
gra-, in stage four you have to have fevers for pers-, persisting for more than 
a month involuntary weight loss at greater than ten per cent of baseline so in 
other words if you weighed ten stone you've got to have lost more than a stone 
in a short period of time if your natural body weight is ten stone and you've 
gone down below nine stone then you're in then you're in full-blown AIDS by 
definition you need to have had diarrhoea for more than a month untreated now 
you should appreciate and i mean i'll come on to say something about this later 
on there are now of course quite a lot of antiviral agents that are being used 
at least in some parts of the world to treat AIDS infection but untreated the 
median time from entering stage four to death is about ten months it doesn't 
differ very much from one part of the world to the other it tends to be 
slightly shorter in the developing world and that's probably got simply to do 
with the fact that people are generally more 
malnourished in the developing world so in other words you know their general 
state of health is poorer to start with so once they go into AIDS they die 
quicker basically than do people in the developed world but we're only talking 
about a matter of two or three months either way it is a very unpleasant death 
you know i mean it's a lingering death you're ill for several months you have 
massive weight loss people end up bleeding often from all the orifices of the 
body they've got all these opportunistic infections it's a very unpleasant way 
to die there's no doubt about that okay all right let's move on then from a 
description of the disease to say something about the current situation 
globally okay now remember i've handed you out all these handouts so the slides 
i'm about to show you don't need to copy down but you do need to be aware of 
these figures and how they're derived once H-I-V once AIDS became clearly an 
important progressive 
ecidem-, e-, epidemic the World Health Organization set up a task force to 
measure the impact to measure the epidemic and its impact globally and this 
task force now produces a a global report annually in December and so what i'm 
going to show you are the figures from December nineteen-ninety-seven and in a 
month's or so's time there will be figures coming out for December nineteen-
ninety-eight right this gives you an indication of the W-H-O's estimate of the 
number of adults and children estimated to be living with H-I-V infection at 
the end of nineteen-ninety-seven let me stand here it's easier now the first 
thing that you can see is the global figure at the bottom thirty-point-six-
million the W-H-O estimates thirty-point-six-million people globally living 
with H-I-V at the end of nineteen-ninety-seven what does that mean in terms of 
the global population it means about one in 
ha-, one in one-hundred adults so one in a hundred adults round the world is H-
I-V positive now remember that the median time between infection and full-blown 
AIDS is now established in developed countries such as North America to be 
about ten years right around about ten years in the developing countries the 
median time between infection and full-blown AIDS is about eight years it's not 
that much less in untreated remember you're going to die in about a year just 
under a year so what do these figures mean these figures mean that in sub-
Saharan Africa we can expect somewhere in the excess of twenty-one-million 
deaths in the next ten years 
nm0239: okay in Latin America one-point-three in the Caribbean three-hundred-
thousand in North America approximately a million people northern Africa two-
hundred-thousand Europe half-a-million eastern Europe central Asia two-hundred-
thousand eastern Pacific four-hundred-and-twenty-thousand south-east Asia six-
million Australasia 
relatively small numbers you can see from these figures that the area of 
greatest importance in terms of the the epidemic is sub-Saharan Africa 
something like two-thirds of the total number of people infected are in the 
countries referred to as sub-Saharan Africa those are the f-, those are the 
figures for adults and children of those about a million are children under the 
age of fifteen years and predominantly those children have been infected at 
birth the chance of a pregnant woman passing on the infection to her child at 
birth varies somewhat from country to country but is roughly thirty per cent 
and of course these children are infected and infectious as a result although 
in the asymptomatic period because of the low levels of virus you're not very 
infectious and they're going to die before their tenth birthday the majority of 
them okay you can see again that the the f-, place where the figure is largest 
is sub-Saharan Africa almost all of 
the million- plus is in sub-Saharan Africa what about the number of deaths from 
the beginning of the epidemic until the end of nineteen-ninety-seven so this is 
a cumulative total how many people have died of AIDS in the last almost twenty 
years seventeen eighteen years you can see that the cumulative total is now 
eleven-point-seven-million of which approximately nine-and-a-half-million this 
thing is really giving up the ghost approximately nine-and-a-half-million again 
are in sub-Saharan Africa four-hundred-and-twenty-thousand in North America two-
hundred-thousand in western Europe estimated deaths in children of those eleven-
point-seven-million it's estimated that two-point-seven-million of those are 
children under the age of fifteen estimated deaths during nineteen-ninety-seven 
two-point-three-million the number of deaths is accelerating of course as we 
get further into the epidemic the total number of infected people er 
is getting larger and of course there are more people who have now been 
suffering from infection for a longer period of time and so they are starting 
to die in large numbers two-point-three-million of which one-point-eight-
million died in sub-Saharan Africa in the last year in the in the year of 
nineteen-ninety-seven we're talking big numbers here as you can see i mean you 
will have seen if you've read the news that it's estimated that this is on a 
par with the number of people dying from malaria each year estimated that half-
a-million children died from last year from H-I-V infection this is an 
interesting figure the estimate of the number of people who newly acquired H-I-
V during nineteen- ninety-seven let me get to that on my er five-point-eight-
million that's about a hundred-and-sixty-thousand people a day being infected 
roughly again the great bulk of them in sub-Saharan Africa nearly four-point 
nearly 
well just exactly four-million of the five-point-eight-million being infected 
in sub-Saharan Africa number's much lower in North America and western Europe 
in fact in North America the infection rate is declining number of children you 
can see nearly six-hundred-thousand children infected last year but look how 
many of those six-hundred-thousand it's estimated were infected in sub-Saharan 
Africa what does this mean what are the social consequences of some of these 
numbers this is an estimate of the number of children orphaned by AIDS during 
the epidemic so it's estimated that something like eight-point-two-million 
children globally have been orphaned by their parents dying of this disease of 
which nearly eight-million are in sub-Saharan Africa okay i mean these are 
really these are numbers that clearly you only have to stop and give a little 
bit of social thought to this to realize these are numbers that have profound 
social consequences you 
know these countries are having to deal with eight-million children under the 
age of fourteen who have no parents okay this is not a small orphan problem 
this is an enormous problem and of course these are the countries that are 
really with the exception of South Africa itself are really very poverty-
stricken countries what can we say about the regional statistics okay the W-H-O 
divides the world into a number of regions i mean the interesting thing about 
this table i'm not going to go through it in great detail but i want you to 
focus your attention on this column here this is adult prevalence rate so this 
is the number of adults in your population who are infected and if we take sub-
Saharan Africa as a whole it's seven-point-five seven-point-four per cent now 
the consequences of that are that unless there's some treatment that is come up 
with that is be able to be that is cheap enough to be used on a very large 
scale in ten 
years' time seven-and-a-half per cent of the adult population in sub-Saharan 
African is going to be dead okay i mean again you just have to stop and think 
about what the enormou-, and this hides some really even more horrific figures 
for example in Botswana something like twenty-four per cent of the adult 
population is H-I-V positive think of the consequences for example of Coventry 
of going into Coventry and killing in a ten year period twenty-four per cent of 
the adult population of Coventry how would the city of Coventry survive as a 
social structure how would it run you know it's not easy to see how these 
societies socially are going to cope with the consequences of this infection 
yeah these are very large numbers and nobody really knows actually what are 
going to be the the social consequences you can see that they're bound to be 
profound but in the end no one is sure exactly what they will be 
nm0239: this is a a global view of infection at the end of 
nineteen-ninety-seven and this is really just a way of of showing you where the 
hot spots are basically and of course it just reiterates that the hot spots are 
in sub-Saharan Africa s-, the cool spots appear to be places like er Russia 
north Africa western Europe Australasia these diagrams are are there to give 
you an idea of the spread of the disease over time and you can see here is what 
it looked like in the early nineteen-eighties in fact the epicentre in Africa 
in the early nineteen-eighties was n-, the northern region of sub-Saharan 
Africa areas such as Kenya Uganda but over the years what you can see is it 
pread-, spreading progressively out from that epicentre and particularly 
spreading progressively south and so now the epicentre is down here countries 
like Namibia Botswana Zimbabwe and look at the figures estimated percentage of 
adults in the fifteen to forty-nine group who are infected between sixteen and 
thirty-two per cent in these 
countries here's a similar thing for South America and the Caribbean area you 
can see that the values are much lower but they're still in some countries 
quite profound i mean two to eight per cent of your population in Guyana for 
example if you lose eight per cent of your adult population in a ten year 
period that's going to have pretty dramatic social consequences this is er 
spread of H-I-V throughout south-east Asia and the key thing to pick up here is 
the very rapid spread in the latter part of the nineties in India and the 
countries here Thailand miran-, Miranmar or what we used to know as Burma 
Bangladesh you can see the figures are between half a per cent and eight per 
cent prevalence i'll throw you out a statistic from from last year's er report 
and i i will put copies of these reports which can actually be downloaded from 
the W-H-O web site but i'll put copies in the library of the nineteen-ninety- 
seven end of ninety-seven figures 
so that you can read through it it's about a thirty or forty page report and it 
gives much more detail than i am able to give in this lecture about the numbers 
in different parts of the world but for example in India the main route of 
spread of H-I-V in India is by heterosexual contact in the area around Bombay 
the W-H-O estimates that there are a hundred-thousand prostitutes with an 
average a five clients a night and greater than twenty per cent of them are H-, 
of the prostitutes that is are H-I-V positive now if you just think about the 
implications of that in terms of a explosive spread of disease okay and you'll 
see in a minute something about some some figures about the number of people 
using condoms in some of these areas that are undergoing explosive spread of 
the disease this is this is a a table that's important to look at because this 
gives some idea of of the picture now what this is telling you is the 
proportional increase in 
prevalence rates bet-, in the last three years so this tells you where things 
are spreading where the disease is spreading most rapidly not surprisingly some 
of the s-, countries of sub-Saharan Africa come into it but look at this i mean 
this is a very worrying thing in the former Soviet Union they've seen a greater 
than hundred per cent increase in prevalence rate in the last three years okay 
so i've already given you this figure more tha-, about a hundred-and-sixty-
thousand new infections a day more than ninety per cent of the infections are 
in developing countries the important point about that is that whereas as i'll 
come on to in later lectures there are now AIDS therapies available A-Z-T 
various protease inhibitors these are all expensive and there's just no chance 
whatsoever in the foreseeable future that these therapies are going to be used 
in these developing countries they simply cannot afford to do it about sixteen-
hundred of this 
hundred-and-sixty-thousand are children under the age of fifteen that's per day 
we're talking about fourteen-thousand about this is the important point that i 
haven't alluded to before because i've talked when i was talking yesterday 
about the initial phase of the the epidemic in North America where the high 
risk group were homosexual males you remember i said to you that there was a 
profound change in their social behaviour associated with the o-, the spread of 
the epi-, epidemic from one of high promiscuity I-E high risk to one of 
essentially monogamy they became married more or less and as a result the 
infection rates in homosexual males in North America dropped dramatically but 
it is a sexually transmitted disease globally forty per cent of the people 
being infected are women fifty f-, per cent are in the fifteen to twenty-four 
age group they're in your age category okay globally i should just say in 
passing in case case i forget to mention it again for women who get infected if 
you're infected with H-I-V about the worst thing that can happen to you is to 
get pregnant and the reason why that's a problem is because one of the 
consequences of pregnancy is a natural immunosuppression so as a result of 
becoming pregnant a woman will naturally immunosuppress that is a question of 
preventing rejection of the foetus of course now if you're suffering from an 
immunosuppressive disease if you naturally immunosuppress yourself that's bad 
news and a very common scenario for H-I-V infected women who become pregnant is 
the the becoming pregnant tips them over from being asymptomatic into suffering 
from AIDS they're suffering from AIDS so at the time of delivery there'll be a 
lot of virus around high chance of infecting the child or a common scenario is 
the child is born is infected the mother dies within a few months three or four 
months of birth you're left with an infected baby that's orphaned and is itself 
going to die before the age of ten 
almost certainly who's going to look after it who's going to want to foster an 
H-I-V infected child it's not not a thing that's you know these are these are 
er facts that have profound social consequences like i've tried to emphasize 
over and over again now this is just a reiteration of the tables i showed you 
before cumulative numbers and also for children i'll pass over those relatively 
quickly here are some figures for southern Africa looking at prevalence rates 
in different states different provinces of southern Africa and look at the 
tracking since the early nineteen-nineties since nineteen-ninety through to 
nineteen-ninety-seven just look how fast the epidemic is spreading you've gone 
from you know about one per cent one or two per cent in Kwazulu and Natal in 
nineteen-ninety one to two per cent of adults being infected which itself is 
bad enough to now greater than twenty-five per cent adults infected 
in that small province similar figures for the s-, Soviet Union newly number of 
diagnosed infections starting in nineteen-eighty-seven and running through to 
nineteen-ninety-seven the key feature to look at is here look what's happened 
in the last two years you've got an exponential growth going up from less than 
five-hundred to fifteen-hundred to four-and-a-half-thousand [sniff] this is 
transmission route for the Soviet Union what you can see is that the main route 
of transmission in the Soviet Union at present is intravenous drug abuse the 
use of uncontaminated er the use excuse me of contaminated needles following 
intravenous drug abuse that's the most prevalent cause of infection one of the 
things that you see when social structures break down and you get sexually 
transmitted diseases is it isn't only H-I-V that's a problem here you see the 
figures for some of the former Soviet Union states Belarus Moldova fede-, 
Russian Federation and Ukraine for syphilis from nineteen-seventy-six to 
nineteen-ninety-seven what you can see is nothing much is happening pretty low 
levels to nineteen-ninety-one and then up it starts to come this is an 
interesting figure for a number of countries of southern Africa this is a life 
expectancy calculated life expectancy value now what you can see is that from 
the nineteen-fifties through to the middle eighteen middle nineteen-eighties 
the life expectancy in Africa was increasing this is a mark of man being able 
to combat infectious diseases improvements in combating infectious diseases and 
general malnourishment is resulting for example in Botswana in an increase of 
in the average life expectancy from about forty-three up to over sixty not too 
different from what the life expectancy was in dev-, is in developed countries 
in the upper sixties i think it's sixty sixty-seven for man and seventy-three 
for woman if i remember rightly but you can see in the last 
ten years it's dropping back again in all of these countries some more quickly 
than others the ones it's dropping back in most quickly are the ones with the 
highest prevalence rate for H-I-V infection so you know not to put too fine a 
point on it this is almost like a biblical plague here in these countries i 
mean this isn't just capping off your life expectancy it's actually reducing 
life expectancy in the population as a whole by contrast in western Europe what 
you can see is that it looks like in western Europe the infection is being got 
under control in the sense that the number of new AIDS cases is now actually 
dropping now that's a combination of a reduction in infection rates and also 
the increasingly widespread use of antiviral chemotherapy holding people in the 
asymptomatic phase so it's not solely due to changes in the infection rate well 
this is just another i mean you can i mean i won't go through this this is 
just impact of AIDS on under child fi-, under under five child mortality rates 
in a number of African countries that d-, with and without AIDS you can see 
that of course AIDS have a AIDS has a dramatic effect mother to child 
transmission you can see er how it's rapidly gone up transmission by er mother 
to child transmission direct transmission of H-I-V or transmission through 
breastfeeding they both go up you can trans-, transmit H-I-V by breastfeeding 
well this is just another way of depicting the graph i showed you earlier this 
is increased mortality rates among men in the fifteen to sixty age group based 
on whether or not whether or not there is er high levels of H-I-V proportion of 
adult mortality attributable to H-I-V well you can see that in a small Ugandan 
town it's about two-thirds to three-quarters of it so this has become a really 
major killer well you can take from this what you will i'm not 
going to go through all of these in great detail this is an interesting one 
that i alluded to earlier the percentage of sexually active men using condoms 
by age and group and type of partner in nineteen-ninety-six for couple of 
countries where there is a big H-I-V problem despite the fact that they've got 
a big H-I-V problem and it's due to heterosexual spread look how you know in 
Malawi where there'll be fifteen to twenty per cent of the adult population is 
infected so your chance with unprotected sex of being infected is very high 
nevertheless still only twenty-odd per cent of males are using condoms and just 
to show you that i'm not sexist okay this shows you the figures for women okay 
same thing i mean very low levels of women using condoms and what's the er i 
alluded earlier to the fact that if you're H-I-V positive as a woman about the 
worst thing that can happen to you is that you get pregnant look at the 
pregnancy rates for by 
the age of nineteen in a selection of these countries that are most highly 
affected okay i mean in virtually all case well in all cases including Senegal 
it's greater than forty per cent so that would mean that you know forty per 
cent of you in this room if you were in these countries forty per cent of the 
women that is would have already had a child by now okay and of course with 
high prevalence rates of H-I-V infection this is a real problem okay we'll 
we'll pass over that and come back to that later what i've tried to give you 
then in those handouts and in the slides i've gone through is a picture 
globally of the disease as at the end of nineteen-ninety-seven the numbers are 
very large of course yeah and the disease is having profound social 
consequences around the world the reason i've laboured in going through this is 
because as i said to you when you go out of here with a degree in microbiology 
and virology and you 
tell somebody you know something about viruses almost certainly the virus that 
they will ask you about is H-I-V and they will expect you to be reasonably 
informed and what they won't want to know from you is how tat and rev works 
okay what they'll want to know from you is what's the sort of number of people 
who are suffering from this where is it the biggest problem what are your 
chances of being infected okay now on the end of the handout i've tacked out 
given out to you i've tacked on the last two monthly reports from the Public 
Health Laboratory Service of the situation in the United Kingdom and the best 
one to look at is actually the one from the end of August because that gives 
you some breakdown by region as to the numbers involved and the important point 
i can't i can't find the table i'm looking for in the sheets i brought with me 
yeah oh yeah it's it's this table here it's actually in the September one 
not i think it's the very last page of the handout i gave you what you can see 
is that there's something like thirty-thousand well just over thirty-thousand H-
I-V positive people in Britain somewhere over three-and-a-half-thousand of them 
have died of AIDS so far it's not a uniform distribution across the country er 
the West Midlands there are about a thousand people thousand H-I-V positive 
people in the West Midlands which compares to something like fifteen-thousand 
as you can see nearly sixteen-thousand in North Thames which is north London so 
the infection in the United Kingdom is pretty localized there is it's still the 
case that the epidemic in the United Kingdom the highest risk f-, risk factor 
is still homosexuality it's still true that more homosexuals many more 
homosexuals than heterosexual spread but as you can see from one of the tables 
heterosexual spread is starting 
to incur so there is depending again on the area in the country where you are 
there is a finite risk of heterosexual spread of this disease if you start 
having large numbers of sexual partners and just as it was the case in the 
homosexual spread in North America that i talked about yesterday the same is 
true in heterosexual spread in unprotected sex the more partners you have the 
greater is your risk of contracting the disease it's a straightforward linear 
relationship one against the other okay all right i i'll stop a little bit 
early because i've reached a natural break point and i'll continue tomorrow 
when i shall start talking about the virus that causes this disease rather than 
the disease itself thanks very much indeed