According to the National Institute of Allergy and Infectious Diseases (NIAID), over one million people in the United States are living with the Human Immunodeficiency Virus (HIV). Infection with this virus progresses through several stages, finally ending in the Acquired Immunodeficiency Syndrome (AIDS). The different stages have certain peculiar characteristics. There is a flexible clinical staging of the infection based on the studied progression of the disease. The Centers for Disease Control and Prevention (CDC) uses the blood levels of CD4+ T-lymphocytes, a subset of white blood cells targeted by HIV, to further define these stages for standardized records.
Acute HIV Infection (AHI)
This stage, according to the Department of Health and Human Services website AIDS.gov, is also called primary HIV infection or acute retroviral syndrome (ARS). This is the earliest stage of the infection and typically takes place within the first 2 to 4 weeks, but sometimes up to three months, of the entry of the virus into the body. Most people, according to NIAID, report a flu-like illness in this stage of the infection with fever, chills, rashes, muscle aches, sore throat, fatigue, mouth sores and swollen lymph glands. Routine blood screens may be negative at this early stage, but the blood level of infective viral particles is at its maximum, making it the most dangerous stage for spreading the disease.
Chronic or Latent Infection
This stage follows the acute infection and lasts for a very variable length of time, from a few months up to ten years, according to AIDS.gov. The blood screens are usually positive, but there are no signs of illness. According to the NIAID, 21percent of people infected with HIV are unaware of their status. They would usually be in this phase of the illness.
Late Infection and AIDS
This is the latest stage of the infection with HIV, when the virus has reduced the CD4 count (the number of CD4+ T-lymphocytes) down to below 200/µL (from the normal 500 to 1600/µL, according to NIAID). Infections that would normally have been easily handled by an intact immune system, called opportunistic infections, typically start appearing in the body at this stage of the illness. The CDC calls these infections and certain cancers, which also appear at this stage, AIDS-defining conditions. The presence of these conditions in a patient with a positive blood test at anytime is classified as AIDS, irrespective of the CD4 count.
The AIDS-defining conditions that characterize this stage of the illness include recurrent or multiple bacterial infections like skin sepsis, pneumonia, enteritis, Salmonella septicemia and mycobacterial infections; fungal infections like candidiasis, histoplasmosis and coccidiomycosis; protozoal infections like toxoplasmosis, pneumocystis carinii pneumonia, isosporiasis and cryptosporidiosis; viral infections including cytomegalovirus and herpes simplex infections; and forms of cancer like Kaposi's sarcoma, non-Hodgkin's lymphoma, anal and cervical cancers.
Other signs of the late stages HIV/AIDS are HIV-related dementia, progressive multifocal leukoencephalopathy and a wasting syndrome.
The CDC HIV/AIDS Case Definition
This is a format developed by the CDC for standardizing public health records of HIV/AIDS cases. It is made up of four stages. Stage one is the earliest form of the disease with a positive blood test and a CD4 count above 500/µL in the absence of any AIDS-defining conditions. Stage two is the intermediate stage with the CD4 count between 200 and 500/µL, a positive blood test and no AIDS-defining conditions. Stage 3, referred to as AIDS, is the late stages of the disease with a positive blood test and either a CD4 count below 200/µL or the presence of an AIDS-defining condition. The fourth stage is termed Stage Unknown and is supposed to include those with a positive blood test, but no reported CD4 count or AIDS-defining conditions.
References
- National Institutes of Allergy and Infectious Diseases: HIV/AIDS: Quick facts
- Centers for Disease Control and Prevention: Case Definitions for HIV Infection
- AIDS.gov: Stages of HIV Infection
- National Institutes of Allergy and Infectious Diseases: Clinical Progression of HIV/AIDS
- Centers for Disease Control and Prevention: AIDS-defining Conditions
