HIV transmission

HIV can be transmitted through the blood (including menstrual blood), semen, breast milk, and vaginal fluids/secretions of infected persons. Transmission to another person can occur if those fluids enter the other person's body. HIV can be isolated from other bodily fluids, such as saliva, sweat, and tears, but the viral concentration is so low that the transmission risk is negligible. HIV cannot be transmitted from coughing or sneezing, sharing household items, or swimming in a pool with someone who is infected.

Transmission is affected by viral fitness (ability of the virus to replicate and cause disease), amount of exposure, and host resistance. There are three main ways in which HIV is transmitted.

Through unprotected anal or vaginal sex. The presence of another sexually transmitted infection (such as an active case of herpes or syphilis) heightens the risk of HIV transmission, as does unprotected sex with someone in the primary (acute) stage of HIV infection. HIV is unable to pass through quality latex or polyurethane condoms.

Through blood-to-blood contact. This mainly happens through the sharing of injecting equipment among drug users. The risk of transmission is high whenever needles and syringes are shared or re-used without proper sterilisation.

Very rarely, HIV infection results from an occupational accident amongst healthcare workers. Fortunately, follow-up studies have shown that 99.7% of all reported needlestick/cut exposures do not lead to HIV infection.

In countries where the blood supply is not screened, transmission occurs through the use of infected blood and blood products. In the past, infected blood products such as the Factor VIII used to treat haemophilia were responsible for causing many HIV infections.

Vertically, from an HIV-positive mother to her baby while pregnant, giving birth, or breastfeeding. In the absence of antiretroviral therapy, the average risk of transmission during pregnancy or delivery is in the region of 10 to 15%, although it will be higher if the mother has primary infection, a high viral load, or has developed AIDS. Breastfeeding carries a risk of transmission and should be avoided if alternatives to breastfeeding (including a safe water supply) are available and affordable.

Brief History of HIV in the United States

HIV was first identified in the United States in 1981 after a number of gay men started getting sick with a rare type of cancer. It took several years for scientists to develop a test for the virus, to understand how HIV was transmitted between humans, and to determine what people could do to protect themselves.

During the early 1980s, as many as 150,000 people became infected with HIV each year. By the early 1990s, this rate had dropped to about 40,000 each year, where it remains today

AIDS cases began to fall dramatically in 1996, when new drugs became available. Today, more people than ever before are living with HIV/AIDS. CDC estimates that about 1 million people in the United States are living with HIV or AIDS. About one quarter of these people do not know that they are infected: not knowing puts them and others at risk.

HIV

HIV stands for human immunodeficiency virus.

This is the virus that causes AIDS. HIV is different from most other viruses because it attacks the immune system. The immune system gives our bodies the ability to fight infections. HIV finds and destroys a type of white blood cell (T cells or CD4 cells) that the immune system must have to fight disease.

For more information view CDC's questions and answers on "HIV Science".

Anatomy of the AIDS Virus

Aids

AIDS stands for acquired immunodeficiency syndrome.

AIDS is the final stage of HIV infection. It can take years for a person infected with HIV, even without treatment, to reach this stage. Having AIDS means that the virus has weakened the immune system to the point at which the body has a difficult time fighting infections. When someone has one or more of these infections and a low number of T cells, he or she has AIDS.

For more information view CDC's questions and answers on "HIV Science".

Electron microscope image of HIV, seen as small spheres on the surface of white blood cells

Source: ©Centers for Disease Control and Prevention (CDC) [basics#hiv]
Last updated: 03/08/2008

Fact Sheet Categories To see a list of fact sheets in each category, click on the category name. 100	Background Information
120	Laboratory Tests
150	Preventing HIV Infection
200	Living with HIV
400	Medications to Fight HIV
410	Nukes: Nucleoside Analog Reverse Transcriptase Inhibitors
430	Non-Nukes or NNRTIs: Non-Nucleoside Reverse Transcriptase Inhibitors
440	Protease Inhibitors
460	Attachment and Fusion Inhibitors
470	Other Drugs to Fight HIV
480	Strengthening the Immune System
500	Opportunistic Infections and Related Diseases, and Their Treatment
530	Drugs to Treat Opportunistic Infections
550	Side Effects and Their Treatment
600	Patient Populations
650	HIV and Related Diseases
670	Hepatitis C
700	Alternative and Complementary Therapies
800	Nutrition
900	Internet Bookmarks for AIDS
1000	Index of Fact Sheets

WHAT IS LAMIVUDINE?

WHAT IS LAMIVUDINE?

Lamivudine (Epivir®), is a drug used as part of antiretroviral therapy (ART). It is manufactured by GlaxoSmithKline. Generic versions made by Ranbaxy and Aurobindo Pharma were approved in 2005 for sale outside the US. Lamivudine is also known as 3TC.

Lamivudine is a nucleoside analog reverse transcriptase inhibitor, or nuke. These drugs block the reverse transcriptase enzyme. This enzyme changes HIV’s genetic material (RNA) into the form of DNA. This has to occur before HIV’s genetic code gets inserted into an infected cell’s own genetic codes.

WHO SHOULD TAKE LAMIVUDINE?

Lamivudine was approved as an antiretroviral drug (ARV) for people with HIV infection. It has been studied in adults and children over 3 months old.

There are no absolute rules about when to start ART. You and your health care provider should consider your CD4 cell count, your viral load, any symptoms you are having, and your attitude about taking ART. Fact Sheet 404 has more information about guidelines for the use of ART.

If you take lamivudine with other ARVs, you can reduce your viral load to extremely low levels, and increase your CD4 cell counts. This should mean staying healthier longer.

A different formulation of lamivudine has been approved for people with hepatitis B. Some people with HIV had their hepatitis B get worse after they stopped taking lamivudine. Get tested for hepatitis B before you start taking lamivudine to treat HIV. If you have hepatitis B and stop taking lamivudine, your health care provider should carefully monitor your liver function for several months.