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HIV is spread primarily by unprotected sex (including anal and vaginal sex), contaminated hypodermic needles or blood transfusions, and from mother to child during pregnancy, delivery, or breastfeeding. [18] Some bodily fluids, such as saliva, sweat, and tears, do not transmit the virus. [19] Oral sex has little risk of transmitting the virus. [20]
Figure 1. Early Symptoms of HIV. The stages of HIV infection are acute infection (also known as primary infection), latency, and AIDS.Acute infection lasts for several weeks and may include symptoms such as fever, swollen lymph nodes, inflammation of the throat, rash, muscle pain, malaise, and mouth and esophageal sores.
The CD4 T-cell count is not an HIV test, but rather a procedure where the number of CD4 T-cells in the blood is determined. A CD4 count does not check for the presence of HIV. It is used to monitor immune system function in HIV-positive people. Declining CD4 T-cell counts are considered to be a marker of progression of HIV infection.
In a survey of 229 HIV-seronegative injection-drug users in New York City, mean CD4+ T-cell counts of the group were consistently more than 1000 cells/μL of blood. Only two individuals had two CD4+ T-cell measurements of less than 300/μL of blood, one of whom died with cardiac disease and non-Hodgkin's lymphoma listed as the cause of death.
After the virus enters the body there is a period of rapid viral replication, leading to an abundance of virus in the peripheral blood. During primary infection, the level of HIV may reach several million virus particles per milliliter of blood. [2] This response is accompanied by a marked drop in the numbers of circulating CD4 + T cells.
Long-term nonprogressors typically have viral loads under 10,000 copies /mL blood, [3] do not take antiretrovirals, and have CD4+ counts within the normal range. [4] Most people with HIV not on medication have viral loads which are much higher. It is estimated that around 1 in 500 people with HIV are long-term nonprogressors. [5]
CD4 testing shows the strength of the immune system, but does not report viral activity. As established by the Centers for Disease Control and Prevention (CDC), a person with HIV and a CD4 count below 200 or a CD4 percentage below 14% is considered to have AIDS. [5]
An uninfected person has 500-1500 CD4 T cells/μL of blood. When this count lowers to less than 500 CD4 T cells/μL, opportunistic infections can occur where the immune system is no longer able to fight pathogens it would have easily cleared in an unimpaired state. The infection progresses to AIDS when the count falls below 200 CD4 T cells/μL ...