About 80% of HIV transmission in Thailand was heterosexual, as compared to about 10% in the USA and some other western countries (as of the time I wrote this in the 2000s). So why was the heterosexual transmission rate by unprotected sex much higher in Thailand than in western countries? One answer is because of a different subtype of HIV virus in Thailand. To understand this, read this section.

AIDS (Acquired Immune Deficiency Syndrome) is caused by the HIV-1 virus (Human Immunodeficiency Virus). However:

There are many sub-types of HIV virus, HIV subtype A, subtype B, and on thru subtype F, plus a subtype O, much like hepatitus has hep-A, hep-B, etc., and this may make HIV in Thailand significantly different from HIV in the west.

In general, it is common for a particular kind of virus (common flu viruses and others) to have different strains, some of which are much more easily transmitted than others.

In Thailand, the primary means of transmission of HIV is by heterosexual sex, overwhelmingly HIV subtype E. A second group is intravenous drug users (IDU's), most of whom are infected with HIV subtype B, the subtype most common in western homosexuals and IDU's, and which is apparently difficult to transmit heterosexually.

In the west, the prevalent HIV subtype B has as its primary means of transmission: anal sex (due to the abrasions of an unlubricated and tight tract which give the virus access to the blood), intravenous drug use (needle sharing between drug users), blood transfusions, hemophilia (people who need blood transfusions and who got donated blood with HIV before the hospitals could detect HIV), and with heterosexual transmission accounting for only about 10% of all cases. Subtype E is found in only a tiny minority of cases in the west, and is often traceable to travellers from Thailand.

For more than 20 years, Thailand has had HIV subtypes B and E. However, it is subtype E which has taken off in the heterosexual population. This has suggested that there are significantly different degrees of contagiousness between the two subtypes as regards heterosexual transmission.

It might be a common deadly mistake by western men to have unprotected sex with prostitutes in Thailand based on a lack of education and understanding of the difference between HIV subtype B in the west and HIV subtype E in southeast Asia.

Southeast Asia predominantly has subtype E, whereas other regions of the world have different predominant subtypes (the USA has subtype B, Africa has A, C and D, and so on). Thailand has a mix of two subtypes, subtype B and subtype E. Subtype B is mainly found in northern Thailand among intravenous drug users. Subtype E is what is predominantly found among prostitutes and heterosexuals. For example, a Chulalongkorn University clinic in Bangkok which had large numbers of HIV enrolled patients for studies found that 92% of male heterosexuals were infected with HIV subtype E, whereas 79% of intravenous drug users (IDU's) were infected with subtype B. (In both cases, practically all the rest were infected with the other subtype of HIV.)

HIV infection is highest in northern Thailand near the Golden Triangle, due to the opium and intravenous drug use in that area. Northern Thailand is also where the highest concentration of HIV subtype B can be found.

Subtype E actually appears to be a "recombinant" mutation, where a cell somewhere in the world was infected by two different strains of HIV at the same time, like "virus sex", resulting in genes "combined" from both. Subtype E is thought to be a combination of subtype A found in western Africa combined with another subtype, perhaps with subtype B which is dominant in North America, Europe, Australia, and Japan. (Subtype A is commonly found in other recombinant forms, too.)

Prostitution is rampant in many countries in Asia and the world, yet the percentage of the population in Thailand that are HIV carriers (approximately 2%) appears much higher than in other places with prostitution, after adjusting for per capita infection rates.

A research report at the University of New South Wales in Sydney, Australia, has an analysis that concludes: "it has been estimated that the heterosexual HIV transmission rate in Thailand (where subtype E predominates) is fifty-fold higher than that observed in USA and Europe (where subtype B predominates)."

One of the best medical web research sites (geared for physicians) has an in-depth research report conducted in Thailand, which reports: "One of the earliest studies suggesting differences in efficiency of transmission among HIV-1 subtypes was a cross-sectional seroprevalence study of HIV-1, presumed subtype E, in Thai military conscripts infected by commercial sex workers (CSWs).[52] Using mathematical modeling, researchers estimated that the probability of female-to-male HIV-1 transmission per sexual contact was approximately 1 in 30 to 50 contacts; previous estimates for HIV-1 subtype B were estimated at 1 in 500 to 1000 contacts. A second Thai study compared serodiscordance in couples in which the index case was either infected with subtype E from CSW contact or subtype B from intravenous drug use (IVDU). After controlling for factors known to affect transmissibility (eg, STDs, advanced disease), subtype E was associated with a much higher rate of seroconcordance, suggesting a difference in the intrinsic properties of the subtypes, with enhanced heterosexual transmission in HIV-1 subtype E.[53] One recently published report suggested that this apparent enhanced heterosexual transmission of subtype E may be due to increased replication in Langerhans' cells, which are located in the vaginal mucosa and may be the cell types that first become infected during heterosexual transmission of HIV-1.[54] The data from these studies, and the predominance of HIV-1 subtype B in the Americas and Europe where homosexuality/bisexuality is the major risk behavior, have led some investigators to conclude that subtype B is less efficiently transmitted heterosexually than the other subtypes, particularly subtype E." Reference:

Reports that analyzed only HIV in general, without specifying the subtype, are apparently not completely applicable to situations in Thailand.

Overall, in Bangkok, at a hospital which has the subtype statistics for more than 2000 HIV infected patients, approximately 82% have subtype E (95% of subtype E infections contracted heterosexually), and approximately 13% have subtype B (70% of subtype B infections contracted by intravenous drug use). (Reference: RetroConference 99.) Stated differently, non-IDU's (i.e., heterosexuals, homosexuals and hemophiliacs who do not inject drugs) accounted for approx. 30% (85/284) of subtype B infections, but approx. 95% (1723/1820) of subtype E infections.

Subsequent studies have confirmed that HIV subtype E is more contagious than subtype B for heterosexuals, and there doesn't seem to be any significant disagreement about that, but there is disagreement about how much more contagious subtype E is -- from less than twice as contagious to 50 times as contagious, or maybe something in-between.

It has been determined in general that HIV is more easily transmitted when another sexually transmitted disease is present. How much this applies to subtype B vs. subtype E is not clear to me at this point, since subtype B appears to need access to the blood more than subtype E, and thus may need to take advantage of herpes lesions, inflammation of the urethra due to other STD's such as chlamydia, NSU, or gonorrhea, scratches due to teeth during oral sex, etc.

In any case, to compare the chances of getting HIV by unprotected sex in the west vs. the chances in Thailand are not comparable due to factors including the following:

  1. HIV subtype E vs. HIV subtype B
  2. The higher percentage of HIV carriers in Thailand
  3. The preponderance of other STD's such as NSU which increase transmissibility

The rate of spread of HIV in Thailand levelled off in the early 1990's, apparently due to diligent campaigns on condom use by the Thai government and certain NGO's. However, many ex-pats continue to "bareback" (i.e., have sex without a condom) with prostitutes, with more ex-pats doing so after consumption of alcohol.

Some studies estimate that the percentage of prostitutes infected with HIV is approximately 10% in the ex-pat areas of Bangkok. However, these studies have uncertainties due to the biases of their samplings.

A Chulalongkorn study found that "disguised prostitutes", that is, ladies who freelance in shopping malls and the like posing as non-prostitutes but who extract presents (fashion items, mobile phones, etc.) and spending money from quasi-boyfriends in an extrinsically motivated relationship, had HIV infection rates of around 30%. The Chulalongkorn study speculated that the higher rates may be due to lower condom use in these relationships. However, the Chulalongkorn study notes that this was an unexpected finding and based on a statistically small and arguably insignificant sampling.

The best protection against HIV, besides abstinence, is condom use. Condoms are a highly effective protection against HIV.

The most often recommended condom is Durex, especially those with the N-11 spermicidal lubricant which may also help protect against some sexually transmitted diseases. However, some of the very thin and polyurethane ones have been reported by associates to break, including a Durex non-mainstream variety. A larger condom for ex-pats has recently arrived on the local market, often in the form of vending machines in ex-pat areas, and it is called BodyGuard. More information is on the ThailandGuru page on condoms.

Update in December 2006:

One thing I find interesting is that the more contagious subtypes found in Thailand and Africa don't seem to be spreading around the world as quickly as I would expect from travellers. Therefore, I wonder if there is more than one factor here.

Contrary to popular belief among many laymen, subtype E does NOT require blood-to-blood contact to transmit itself. Based on research studies, scientists have found that subtype E attacks the Langerhans cells (LC) exceptionally well, particularly those located on the penis foreskin and in genital mucosa, with HIV subtype E infecting and reproducing itself multiple times more quickly than other strains of HIV. Subtype B prevalent in the US and Europe doesn't seem to have ever had (or possibly lost) the same viral sequences as subtype E for transmission this way.

However, this may not entirely account for increased spread of subtype E in Thailand in view of the slow spread of subtype E to the outside of Thailand, similar to African HIV.

In Africa, there are widespread trends for ladies to dry their vagina before intercourse in order to create more friction for the man and presumably pleasure, rather than a well lubricated vagina. In fact, the ladies often insert powders and herbs and other things. These things can cause irritation and even bleeding, which could account for the increased transmission in Africa, not the particular strains of HIV there (which, again, differ from western countries).

Is there some custom in Thailand which could serve a similar role? I think maybe so, for reasons similar to those in Africa. ("Same-same but different" as is joked here.)

HIV seems to be transmitted mainly thru the prostitution community, not the mainstream Thai community nearly as much, even though many young Thais are promiscuous in their multiple romantic and casual relationships. What do prostitutes do which is different from mainstream Thai ladies? Talk to any guy who goes with prostitutes, whether they are picking up the lady from a bar, going to a massage place, or just a knocking shop. It's all the same -- the lady takes a shower and cleans herself first, and requires the man to do likewise. Unfortunately, this removes natural lubrication.

Of course, prostitutes having mercenary sex are generally not as naturally lubricated as a girlfriend with sincere sexual or emotional attraction to you. However, the cleaning just exacerbates this.

Never, not once, have I ever been with a mainstream Thai lady who stopped the action to go take a shower first, or require that I do so. Same thing with foreign ladies. I don't want to brag here, but for the sake of research and statistics, I've had sex with many foreign ladies and many mainstream Thai ladies, and none -- not one -- ever stopped to take a shower first or required me to do the same. I've rarely had any significant lubrication issues in these encounters.

I've also never had a broken condom, but I've heard of many cases of broken condoms in Thailand. I have spoken with these guys, including brand of condom, and one of the clear answers is that there wasn't enough lubrication for complete penetration before the condom broke. If there wasn't enough lubrication on the condom, then imagine penetration without a condom with the same lady and circumstances! That must be creating irritation, not only in the lady's vagina which makes her more susceptible to infection (and whereby she passes it on), but also to the man by pulling the sides of the front end of the penis so that its inner urethra & mucous membrane are not only exposed but seriously contacted in a way which just doesn't happen with well lubricated sex. That exposes any HIV viruses to the LC targets in the man.

That may be a major part of the answer.

Therefore, pack both condoms and a water based lubricant. Durex sells the lubricant all over Bangkok. There's also K-Y jel available at pharmacies and department stores all over, and it's water based.

Another thing I've found out from talking with guys is that a lot of them who don't like to use condoms (and try not to) will take an antibiotic prior to visiting prostitutes and immediately after, in order to prevent infection by gonorrhea, chlamydia, and other things -- the same broad spectrum antibiotic that is given to cure these diseases, with the theory being that just a little bit will prevent infection by a small number of bacteria, rather than curing a full blown infection several days later. They take these antibiotics shortly before and immediately after sex, but don't need to take them for long, and apparently that works from their reports.

Besides the unrelated issue of developing antibiotic resistant strains due to not completing an antibiotic regimen, I also wonder if attempts to decrease bacterial infection may increase HIV infection.

In the West, heterosexual HIV transmission tends to occur much more frequently when another sexually transmitted disease (STD) is present in the recipient. This infection could result in more LC's being available as part of the body's natural defense against the bacterial STD.

If someone takes antibiotics, they artificially raise the number of infection-fighting T-Cells. This creates more targets for the HIV virus to find in the same places that other STDs come in. Does this cause a significant increase in one's chances of contracting HIV somehow? I don't know, and I've never seen this "prophylactic antibiotic usage" issue researched.

Other STDs may be another

Maybe I'm wrong about all of this, but I've never seen these two issues really analyzed and addressed. If I'm right, then a few lives could be saved here. I welcome comments and critiques.

(However, please don't send emails about HIV not being the cause of AIDS, a common sort of feedback I receive. I'm aware of that small minority school of thought at, and I have read those hypotheses and find them full of one-sided arguments which totally ignore the overwhelming evidence otherwise. These people say HIV doesn't cause AIDS, and many of their believers in Thailand don't use condoms as a result, using this as a rationalization. Let natural selection takes its course. Google the keywords [AIDS HIV myth] and you'll find further discussion as well as thorough refutation of these claims.)  

HIV Blood Tests

If you are going to have a protracted relationship with an individual, it is advisable that you perform an HIV blood test.

There are two different kinds of tests readily available in Thailand. Both take a sample of blood, usually drawn from a vein in the arm, and not very painful to most people. They are:

  1. Antibody tests like the "ELISA" or the "Western Blot"

    These check for antibodies to the HIV virus in the blood. The advantages of this test are that you can get results in about an hour if the hospital or clinic is suitably equipped, and the price is low, typically a few hundred baht. A "negative" result means no detection of antibodies, a "positive" means a detection of antibodies. The disadvantage is that recently infected people may not show antibodies. It takes approximately three months after infection for the body's natural immune system to detect the invading virus, characterize it, and produce sufficient levels of antibodies for the test to detect the antibodies ... for more than 90% of infected people. To get up over 99%, you may have a period of 6 months. Unfortunately, the virus is most far more contagious shortly after infection, before the body starts producing antibodies in sufficient quantities to combat the virus (or be detected by the test), as will be discussed below.

    Notably, false positive results occur in a small percentage of tests. If you get a positive result, it does not mean the person is HIV+. A second, more reliable test must be conducted to ascertain whether or not the person is HIV+. The "ELISA" test is commonly used to check for antibodies because it's cheap and quick, but it sometimes gives a "false positive" in that a positive result of the ELISA test is refuted by a more expensive and more accurate test such as the "Western Blot" test. The ELISA test is often called a "screening test" because it will identify HIV+ people just about as accurately as any antibody test, and its main drawback is that it will cause some extra people to be identified as HIV+ even though they aren't. As one doctor overseas put it, you're more likely to get an ELISA positive than a real HIV positive. It Thailand, it may be different. In any case, an ELISA HIV+ result must be confirmed by a Western Blot or other more accurate test before any HIV+ conclusion can be called accurate.

  2. Antigen tests, which detect the virus directly (DNA and RNA), not the antibodies

    This test can detect the virus in the blood in the period before antibodies are produced. However, it is more expensive (from 800 baht to more than 2,000 baht, depending upon the particular test used and the institution), and usually takes one to three days for a result. It can also fail to detect the virus if an infected person's immune system has strongly suppressed the virus to very low levels in the bloodstream.

It's best to do both antibody and antigen tests. In general, the antibody tests commonly used are more reliable because the antibodies are more easily detectable in the blood stream once the body has started producing them, and continue to be easily detectable for the rest of the life of the infected person, whereas some of the common antigen tests may not detect the little virus in longterm carriers because the antibodies have already reduced the levels of the virus in the blood stream to very low levels. The antibody test works best when the antigen test fails, which is from a few months after infection until death of the infected person. The antigen test works best when the antibody test fails, which is during the first few months of infection when antibodies are low and the virus is replicating without significant suppression by antibodies and usually easily detected by antigen test. If you do only one test or the other, not both, then you are playing with statistical probabilities that may not be as good as you want. If you do both, then you are well covered unless the other person picked up HIV only within the last week or so.

The figure below shows the concentration of HIV vs. antibodies in the blood stream in a typical carrier from the time of infection to the time of the onset of AIDS symptoms years later.

Source: Bangkok Nursing Home hospital/clinic, soi Convent (between Silom and Sathorn)

As you can see above, the level of HIV in the bloodstream is highest by far within the first 3 months, before the antibodies kick in, and these first 3 months are when the HIV carrier is most contagious!.

After infection by the HIV virus, the infected person usually experiences flu-like symptoms from 2 to 12 weeks after infection (i.e., within the first 3 months), in a fairly typical viral infection response. These symptoms are generally some of the following:

  • fever
  • headache
  • fatigue
  • malaise
  • decreased appetite and nausea
  • swollen lymph glands
  • muscular stiffness or aching (myalgia)
  • a skin rash, usually flat to slightly raised (maculopapular)

    These symptoms may last from a few days to two weeks, and then subside.

    After the above symptoms, antibodies to the virus can be detected in the blood. This is called "seroconversion". HIV seroconversion (converting from HIV negative to HIV positive) usually occurs within 3 months of exposure, but sometimes takes 6 months (and in extremely rare occasions may occur up to a year after exposure). Seroconversion is when the body's antibodies kick in.

    So if you want to be safe, then you'd better find a place that will do an antigen test that would detect HIV in your partner within the first few weeks of an infection. For some reason which has escaped me for my 10+ years here, I've never been offered an antigen test, and only been told to use condoms for 3 months and then test again. However, I have found places which will do an antigen test upon request, for between 1500 to 2000 baht, and I've had to wait 2 to 5 days for the result, albeit it's been so many years since I've needed such a test and thus you may need to ask around and also get current pricing, but the wait period will still be similar. Let me tell you what to look for:

    The type of test you want is a "PCR test" (Polymerase Chain Reaction test). It is within a class of tests which "amplify" tiny amounts of an antigen or other genetic substance so that it can be detected. (DNA tests work similarly. These kinds of PCR tests fall within a category called Nucleic Acid-amplification Testing or 'NAT'.)

    There are two kinds of PCR tests according to what they detect: RNA or DNA. The most common is a "PCR RNA test" which is what is used to screen donated blood for HIV (of course donated blood is screened for antigens, not just antibodies!), so these tests are common. The RNA test is more sensitive than the DNA test by a few days, i.e., the RNA test will find an infection a few days before the DNA test. (The DNA test is commonly used on infants born to HIV infected mothers, whereby other tests can give a false positive since antibodies and other substances are transmitted to the baby's blood.)

    So you want the "PCR RNA test", but the "PCR DNA test" is practically as good.

    Known good places to go for an HIV test:

    • The Thai Red Cross, located on Rama 4 Rd. in the Silom-Sathorn area, located by the Snake Farm, near the Sala Daeng skytrain station or the Silom subway station, diagonally across from Suriwongse Road, but note their limited hours

    • Chulalongkorn Hospital, next to the Thai Red Cross, on the corner of Rama 4 Rd and Rajdamri Rd., opposite Lumpini Park and opposite Silom Rd., is good when the Thai Red Cross has closed, but it is a top government hospital and sometimes a little bit difficult for an English speaking person to get things lined up, but the doctors seem good, especially for a government hospital

    • The Bangkok Nursing home, in the Silom-Sathorn area, is clinic/hospital on soi Convent between Silom and Sathorn Roads, but some people have not been satisfied with some of the doctors here in recent years as this business has grown

    • The Klong Tan Hospital, on Petchburi Rd. between Ekkamai (Sukhumvit 63) and Klong Tan (Sukhumvit 71), near where the intersection flyover comes down on Petchburi Rd. This is where I always went when I lived by Ramkhamhaeng University in the 1990s. There was an excellent female doctor there who understands the research issues of HIV extremely well. Small hospital, clinic-like atmosphere.

    • Siriraj Hospital -- one Thailand Guru reader reported feedback that for quality control of HIV tests, he thinks "the HIV reference laboratory for Thailand is at Siriraj hospital. That is they take part in international quality-control programs etc ...." This is one of the few major Thai research and teaching hospitals in the Bangkok area, located in Thonburi at Phran Nok Rd., Tel: 411-0241, 411-3192, 411-4230

    • Paolo Hospital at the Saphan Kwai skytrain station, as suggested by another reader. "You can come back any time after 2 hours for your result. Again, you must see the doctor for your result. They will not give it out by telephone to anyone (even you). Only the doctor is authorized to give you the result face to face... The cost is about 500 baht."

    • On Sukhumvit, one of the most common places, but which I don't recommend, is the world famous Bumrungrad Hospital off Sukhumvit soi 3 (Nana Nua) about halfway between Petchburi and Sukhmvit Roads, to the west, look for the top of the building. I don't want to go into details here, but on many occasions, I and my associates have had bad experiences here, and these statistics are just bad compared to other hospitals here. The English at Bumrungrad is very good (and so is the accounts receivable billing) but I have not been impressed with the doctors or the laboratory reporting. I know this runs counter to their big business reputation, but this is my experience, consistently over 13 years. Also, I've heard that HIV tests are running from 2500 to 3700 baht there in 2008, not exactly encouraging to those on Sukhumvit who should be testing. You can go just about any time of day or night.

    You should be able to get an HIV test at nearly any hospital and many STD clinics, but the above are tried and known places. You should ask first how long it will take to get the results, which is determined by whether they have the testing kits in stock at the hospital, versus sending your blood sample to an outside lab. Test kits for antibody tests are more commonly in stock. Antigen tests take longer even if they have the kits in stock. The particular antigen tests used may differ from site to site, but the antibody tests are usually the ELISA or the Western Blot. However, many other tests have been coming out of R&D and hitting the market.

    To make you and your partner more comfortable, you may want to insist on an anonymous test. Usually, this is done by making up a name before you go in, and filling out all the forms using this name. If they want to see an ID card or passport, just don't bring it with you so that you can say you don't have it. They will usually take your money and do the test using your assumed name, as they should, and I've never heard of a case otherwise. Some hospitals will insist on following their required standard operating procedure (especially if ISO certified) of creating a record for you in their computer database, and issuing a card to you for future visits. (So I have a card with the name Christopher Columbus, which gets a few looks when my name is called in the waiting room.)

    In some places in the world, there are home testing kits, e.g., saliva tests. One saliva test is done with the OraSure product, and is claimed to be 99+% accurate. I don't know if this is available in Thailand. The results take 1 - 2 days.

    This website does not address the issue of HIV treatment, a very large and broad topic. There is no cure for an HIV infection at the time of this writing, though there are many interesting treatments to prolong health against the onset of AIDS.

    Other web links:

    For some very general information on subtypes, including subtype E in Thailand in general:

    Sites recommended by others but which I haven't analyzed yet in detail:, a charity for averting HIV infections, with worldwide programs, and also addresses society's attitudes

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