What are the stages of HIV? How long until progression to AIDS if left untreated?
The first stage of HIV infection is known as acute or primary infection. Most people will experience flu-like symptoms (fever, sore throat, rash, swollen glands) within a few weeks of contracting HIV, but sometimes these can be quite mild. In this stage, the virus spreads rapidly to immune cells throughout the body, especially in the lining of the gut. Large amounts of HIV can be detected in the blood initially, but eventually, the immune system responds and partially suppresses the virus. It can be difficult to detect HIV by blood tests in the first week or two of infection.
Following acute HIV infection, most people enter a period of clinical latency in which they have few or no symptoms. This period may last decades or only a few months, but most infected persons will progress to AIDS over several years. During clinical latency, the amount of virus in the blood often remains stable but detectable, and the CD4 count slowly declines from normal levels (above 500). In rare cases, the infected person’s immune system keeps the viral levels very low and the CD4 count does not drop, even without the use of medications.
If the CD4 count drops below 200 or if a HIV infected person develops one of several AIDS-defining conditions, this indicates progression to AIDS. The immune system is weakened and increasingly susceptible to OIs. Without any treatment, those persons with CD4 counts below 200 have a life expectancy of months to a few years. Once an OI is present in an AIDS patient, overall life expectancy without treatment drops to less than a year.