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Subtype E transmission risk
Hello Doc,
I have read from various websites that there is a HIV Subtype E (or called CRF01_AE a combination of subtype A and E), which is prevalent in Thailand and SE Asia. The transmission rate is reported to be much higher through hetereosexual transmission than the subtype B which is found predominantly in US and the West. Some website quoted it to be 20% higher, some quoted to be as high as 5 to 50 folds. If that's true that would make a one time vaginal intercourse risk to increase from 1/2000 to 1/40 in Thailand. Some even claim that this subtype of HIV can be effectively transmitted through oral sex due to it's ability to attach to the Langerhan cell. When you say that the chance of infection through a single heterosexual exposure is very low, do you only refer to the predominant subtype B in US and other developed country? How about in developing countries? Do you have any updated info on the situation in thailand and which of these info on the websites are true? If it is true that subtype E is more effective through sexual transmission, then by how many percent?
Thanks.
I have read from various websites that there is a HIV Subtype E (or called CRF01_AE a combination of subtype A and E), which is prevalent in Thailand and SE Asia. The transmission rate is reported to be much higher through hetereosexual transmission than the subtype B which is found predominantly in US and the West. Some website quoted it to be 20% higher, some quoted to be as high as 5 to 50 folds. If that's true that would make a one time vaginal intercourse risk to increase from 1/2000 to 1/40 in Thailand. Some even claim that this subtype of HIV can be effectively transmitted through oral sex due to it's ability to attach to the Langerhan cell. When you say that the chance of infection through a single heterosexual exposure is very low, do you only refer to the predominant subtype B in US and other developed country? How about in developing countries? Do you have any updated info on the situation in thailand and which of these info on the websites are true? If it is true that subtype E is more effective through sexual transmission, then by how many percent?
Thanks.
MEDICAL PROFESSIONAL
Dr. Hook's and my replies about HIV transmission risks have generally applied most directly to North America, Western Europe and other industrialized settings; although we don't always say so in individual replies, often we have pointed out that the risks are higher in places like sub-Saharan Africa and parts of Asia. There are no data that allow direct estimation of the numerical risks per exposure from those areas, but probably they are higher than in industrialized settings. However, the difference is due primarily to things like circumcision status, frequency of other STDs, patterns of sexual partnerships (the concept of concurrency), certain sexual practices (e.g., "dry sex"), access to ARVs, and stage of epidemic (the latter two factors resulting in infeced people having higher viral loads). If HIV subtype E has any additional effect beyond those factors, it likely is small.
The rate of HIV in Thailand probably remains higher than in most of the US, but it is dramatically lower than it once was in Thailand. The national prevention campaigns in that country, based largely on intensive awareness campaigns and increased use of condoms, have been highly effective.
In any case, it is not likely that the actual efficiency of subtype E transmission is nearly as high as 1 chance in 30-50, unless the CSW has other factors present, like especially high viral load or another STD. People who are sexually active with CSWs in Thailand of course should use condoms for vaginal or anal sex. Otherwise they shouldn't lose any sleep over the types of HIV that may be present in that country. If they can't handle the stress of worry about it, they should simply not have sex with CSWs in Thailand. Hand wringing over virus is misplaced energy.
The rate of HIV in Thailand probably remains higher than in most of the US, but it is dramatically lower than it once was in Thailand. The national prevention campaigns in that country, based largely on intensive awareness campaigns and increased use of condoms, have been highly effective.
In any case, it is not likely that the actual efficiency of subtype E transmission is nearly as high as 1 chance in 30-50, unless the CSW has other factors present, like especially high viral load or another STD. People who are sexually active with CSWs in Thailand of course should use condoms for vaginal or anal sex. Otherwise they shouldn't lose any sleep over the types of HIV that may be present in that country. If they can't handle the stress of worry about it, they should simply not have sex with CSWs in Thailand. Hand wringing over virus is misplaced energy.
MEDICAL PROFESSIONAL
If you're asking me for absolute certainty, forget it. I never said HIV cannot be transmitted by oral sex, only that it is very low risk. I haven't a clue whether that risk varies from one part of the world to another, or between viral subtypes, but I don't see that it matters. Even doubling a very low risk still results in a very low risk. (Is there really any difference between, say, 1 chance in 20,000 versus 1 in 10,000???) Such figures suggest you could receive a ** by an HIV infected person once a day for 20 years and expect never to catch it.
Please re-read the last sentence above: if even oral sex is going to make you lose sleep about HIV risks, don't do it.
I won't have any further comments.
Please re-read the last sentence above: if even oral sex is going to make you lose sleep about HIV risks, don't do it.
I won't have any further comments.
Then how about unprotected oral sex? You have said there is no documented HIV transmission through unprotected oral sex. So HIV cannot be transmitted through unprotected oral sex applies to everywhere in the world?
MEDICAL PROFESSIONAL
The last sentence is supposed to say "Hand wringing over virus type is misplaced energy".
As the transmission risk data is limited to the HPV strains found in US only, does it mean that most of the low risk assessment in your previous reply only apply to encounter in US only?
Hello Doc,
Maybe you can have a look at the below website. What is your opinion of the info presented in this website?
http://www.thailandguru.com/hiv-aids-thailand.html
The website mention that hetereosexual transmission rate in Thailand is 1/30 to 1/50. In your opinion, do you think that with such high infection rate of the particular subtype in thailand, this subtype would have spread wildly to other countries considering the high number of sex tourists in the country?
You have mention in previous reply that the HIV infection rate among CSW in thailand is rare and is about 5%, is this higher than that in US or other industrialised countries?
Maybe you can have a look at the below website. What is your opinion of the info presented in this website?
http://www.thailandguru.com/hiv-aids-thailand.html
The website mention that hetereosexual transmission rate in Thailand is 1/30 to 1/50. In your opinion, do you think that with such high infection rate of the particular subtype in thailand, this subtype would have spread wildly to other countries considering the high number of sex tourists in the country?
You have mention in previous reply that the HIV infection rate among CSW in thailand is rare and is about 5%, is this higher than that in US or other industrialised countries?
MEDICAL PROFESSIONAL
I don't know much about subtype E and differences in transmission efficiency. However, my understanding that any increased propensity to heterosexual transmission is in the lower range of the possibilities you quote from some websites. From my understanding of the epidemiology of HIV/AIDS in Thailand, it is not plausible that the vaginal sex transmission risk is anything like the higher rates you cite. That said, there are no data. The transmission risk data in the US, published by CDC (e.g., 1 in 1,000 to 1 in 2,000 for unprotected vaginal sex), are of course limited to the HPV strains circulating in the US at the time those analyses were done a few years ago.
Sorry I can't be more helpful than that. Best wishes-- HHH, MD
Sorry I can't be more helpful than that. Best wishes-- HHH, MD
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