Acquired immunodeficiency syndrome, the late clinical stage of infection with human immunodeficiency virus, was first recognized as a distinct syndrome in 1981. It is characterized by progressive damage to the immune system and life-threatening infectious and noninfectious complications.

aids and hiv infection occur worldwide, yet comprehensive monitoring systems are lacking in many countries. The true number of cases is therefore likely to be far greater than the number officially reported. That’s particularly true for underdeveloped nations. The Joint United Nations Pro-gram on hiv/aids estimates that at year-end 2001, 40 million people worldwide were living with hiv/aids.

Still, the risk for international travelers is determined less by where they go than by what they do. Travelers should not use drugs intravenously or share needles for any purpose. They should also avoid, if at all possible, receiving medications from multidose vials that may have been contaminated by used needles. Travelers with hemophilia or insulin-dependent diabetes, or who require routine or frequent injections for another reason, should carry a supply of syringes, needles and disinfectant wipes sufficient to last their entire stay.

The risk of hiv infection for international travelers is generally low. Risk factors include direct contact with blood or secretions and sexual contact with a person who may be infected. To further complicate matters, the blood supply in Third World countries is not adequately screened for hiv.

While no vaccine is available to prevent hiv infection, travelers should be advised that it is preventable. hiv is transmitted through sexual intercourse and/or sharing of needles or syringes; through medical use of blood, blood components, organs or tissues that have not been adequately screened; and perinatally from an infected woman to her infant. hiv is not transmitted through casual contact; air, food or water; contact with inanimate objects; or by mosquitoes or other insects. The use of public transportation by people with aids or hiv infection does not pose a risk of infection to crew members or fellow travelers.

In many countries with high rates of infection, hiv is common in the general population. Condoms, when used consistently and correctly, can prevent transmission of hiv. Travelers who engage in vaginal, anal or oral-genital sexual contact with anyone who is infected with hiv or whose hiv status is unknown should use a latex condom. Those who are allergic to latex should use condoms made of polyurethane or other synthetic materials. In some parts of the world, there is a limited supply and selection of condoms, so travelers who engage in sexual contact with those who may be infected with hiv should carry their own supply.

When a male condom cannot be used properly, a female condom should be considered. Spermicides and barrier methods other than condoms have not been shown to be effective in the prevention of hiv transmission.

In summary, travelers are at risk for hiv infection if they:

1. Engage in sexual contact with an infected person
2. Use or allow the use of contaminated, unsterilized syringes or needles for any injections or other skin-piercing procedures, including acupuncture; use of illicit drugs; steroid or vitamin injections; medical or dental procedures; tattooing; ear or body piercing
3. Use infected blood, blood components or clotting factor concentrates. hiv infection by this route is rare in countries or cities where donated blood and plasma are screened for hiv

For more information about aids and hiv, visit www.cdc.gov.