Types of HIV

Are there different types of HIV? How does HIV affect the body?

There are two types of HIV, HIV-1 and HIV-2, as well as several related viruses that infect certain monkeys or great apes. HIV-1 can be found throughout the world, but HIV-2 is almost exclusively limited to West Africa. HIV-1 is transmitted more easily than HIV-2, and HIV-1 infection progresses more rapidly to AIDS.

HIV infects cells of the human immune system, particularly a kind of white blood cell called the CD4 T-cell. These cells help in identifying and destroying harmful material in the body, including bacteria, viruses, parasites, and even some cancer cells. Over time, HIV infection destroys the CD4 cells, leading to a weakened immune system, certain kinds of infections, severe illness, and death. The infections are often called “opportunistic infections” (OIs) because they are rare or mild in healthy people but can take advantage of the opportunity provided by the HIV-weakened immune system and can be life threatening. The HIV virus can also damage tissue directly, causing neurologic disease, heart disease, and other problems.

The CD4 cell count (sometimes called a T-cell count) is a measure of the number of CD4 cells in one microliter of blood. People with HIV and their health care providers use the CD4 count to monitor the infection over time.