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HEALTH SERVICE INNOVATION
Crescendo and Diminuendo of HIV Epidemics in Thailand and Southeast Asia
Acquired Immunodeficiency Syndrome (AIDS); bridging population; commercial sex worker; HIV prevention and control strategies
Acquired Immunodeficiency Syndrome (AIDS) was first recognized in 1983 when scientists had no clue what the cause of AIDS was. Two years later the etiologic virus, Human Immunodeficiency Virus (HIV), was subsequently identified. HIV/AIDS began spreading into Southeast Asia only a few years after it was first described in the USA. However, the pattern for the predominant mode of transmission was and still is somewhat different from the West. Whilst HIV has been spreading in Europe and North America mostly among men who have had sex with other men (MSM), the virus is being effectively transmitted via heterosexual transmissions in Thailand and her neighboring countries. Although the Thai virus was once reported to have more efficiency in heterosexual transmission in vitro, there is no proof whether this enhanced efficiency can explain preferential heterosexual transmission in Thailand and other countries in mainland Southeast Asia (Indochina, Myanmar, and Malaysia). This article discusses the innovation shift in HIV/AIDS prevention and treatment, with special reference to the bridging population of commercial sex workers (CSW).
In fact, bridging populations such as commercial sex workers (CSW), either male or female, may have played an essential role in shaping predominantly the heterosexual HIV epidemic in Thailand and other Southeast Asian countries (Figure 1). Information on these relationships is particularly useful for the good design of HIV prevention/control strategies.
Strategies for prevention of HIV transmission through sexual routes include behavior modification, safe sex practice, condom use, microbicide gel, circumcision, post-exposure HIV prophylaxis, and more recently pre-exposure HIV prophylaxis. A blood screening policy has been in place for more than 25 years and hence there is now effective prevention of HIV transmission through blood transfusion. Prevention of HIV infection in children born to HIV-infected mothers, using cocktail of anti-HIV drugs, has led to an ultra-low incidence of HIV acquisition in the new born. Whilst prevention of HIV transmission in blood/blood product recipients and in babies born to HIV-infected mother has been hugely successful, prevention strategies for reducing its sexual transmission are still tricky. In some countries, for instance Thailand, campaigns and free condom distribution has led to the control of HIV transmission to a plateau level, but the prevalence and new infection rate is still high (Fig 2). Interventions to further reduce the occurrence of new infections are still on the loose.
Perhaps conventional prevention measures of sexually transmitted diseases (STD) per se are not sufficient to prevent against HIV transmission.
The quantity of HIV (HIV load) is known to be a key factor for the successful transmission. Treatment of HIV/AIDS by anti-HIV drugs leads to a significant reduction in the HIV load, and hence decreases the probability of HIV transmission to uninfected sexual partners. In theory, if the virus load of all HIV-infected persons is fully suppressed by anti-HIV drugs, their partners are very unlikely to contract HIV from them.
Despite several billions of dollars in global investment and some 25 years in the quest for a safe and effective HIV vaccine, we have observed only one successful, though marginally successful, story. The level of protection in vaccinated persons is only slightly more than 30 percent above that of non-vaccinated subjects.
There may be a light at the end of the tunnel, even after Merck’s HIV trial failed to improve the efficacy a few years ago. While we are waiting for a more effective HIV vaccine, other interventions are indispensible for slowing down the epidemic, particularly in the young. We still do not know how long this diminuendo of the HIV epidemic will go on, but hopefully the epidemic will not begin a new crescendo in a new risk group.