The Human Immunodeficiency Virus (HIV) is a retrovirus that attacks the body’s immune system, specifically targeting CD4 T cells. Acquired Immunodeficiency Syndrome (AIDS) represents the most advanced stage of this infection. A person cannot contract HIV from a simple handshake. The virus requires specific conditions and routes to pass from one person to another, clarifying why everyday social interactions pose no risk of transmission.
Why Casual Contact Poses No Threat
The HIV virus is biologically fragile and cannot survive for long periods once exposed to the air or dried on a surface. This lack of hardiness means that contact with inanimate objects presents no danger of infection. Transmission also requires a sufficient dose of the virus, which is not present in most bodily fluids associated with casual contact.
Fluids such as sweat, tears, urine, and saliva do not contain a high enough concentration of the virus to be infectious, even if the person has HIV. Enzymes in these fluids also work to break down and neutralize the viral particles. Activities like hugging, sharing utensils, touching surfaces, or using the same toilet seat are safe because they do not involve the direct, high-concentration fluid exchange required for the virus to establish an infection.
Understanding How HIV Is Transmitted
Transmission of HIV occurs only when specific bodily fluids from a person with a detectable viral load enter the bloodstream or contact the mucous membranes of an uninfected person. These infectious fluids are blood, semen, pre-seminal fluid, vaginal fluids, rectal fluids, and breast milk. The virus must have a direct pathway to a susceptible cell population to initiate a new infection.
The primary route of transmission worldwide is through sexual contact, particularly unprotected vaginal or anal intercourse. This allows infectious fluids to contact the delicate mucous membranes lining the rectum, vagina, and urethra. Sharing needles, syringes, or other equipment used for injecting drugs is another high-risk route because it directly introduces contaminated blood into the bloodstream.
A person with HIV can also pass the virus to their child during pregnancy, childbirth, or through breastfeeding. The use of antiretroviral medication by the mother can reduce this risk of perinatal transmission to less than one percent.
The Difference Between HIV and AIDS
HIV is the virus itself, while AIDS is the syndrome, or late-stage condition, resulting from advanced, untreated HIV infection. The virus attacks the immune system by infecting and destroying CD4 T-lymphocytes, which are white blood cells that coordinate the immune response. A person is diagnosed with AIDS when their immune system is severely compromised, making them vulnerable to opportunistic infections and certain cancers.
An AIDS diagnosis is given when the CD4 T-cell count drops below 200 cells per cubic millimeter of blood, compared to a healthy range of 500 to 1,600 cells/mm³. The diagnosis can also be made if a person with HIV develops one or more AIDS-defining illnesses, regardless of their CD4 count. Modern treatment, known as Antiretroviral Therapy (ART), successfully suppresses the virus, preventing the immune system damage that leads to AIDS.