HIV infection by onprotected homosexual, heterosexual and drug abuse route is prevalent throughout this region.  Transmission had decreased in Thailand during the past 2 decades, mostly due to a huge educational effort on the part of government.  It is still increasing in the neighboring countries.  Travelers must be aware of this and practice abstinence or safe sex at all times.  If you have the misfortune of having experienced an unprotected exposure, report immediately, and not later than 72 hours, to the nearest hospital emergency room and explain the circumstances to the doctor on duty.  He may advise you to take one month of prophylactic anti-HIV therapy.  This is costly and not without adverse side effects.  It also is not 100% effective.  You should have blood tests for HIV and syphilis before it is administered and 3 and 6 months later.  Patients with HIV- AIDS, particularly if not fully treated and having low CD4 cells, are particularly at risk of several bacterial, viral and parasitic infections.  They also tend to form poor antibody responses to most vaccines.  Such patients, traveling in Asia, must be made aware of this and reduce risks wherever possible.