Clinical features
Infection is diagnosed either by detection of antibodies to HIV in the blood or by detection of ribonucleic acid (RNA) in virus particles.
Laboratory Indicators (Markers)
The clinical features are determined by the CD4 lymphocyte count. As the number of virus particles rises (viral load) during the course of the illness, the number of CD4 lymphocytes fall. As the CD4 lymphocyte count falls, especially to below 350/µl, the person becomes susceptible to infection. The majority of life threatening infections and tumours occur at CD4 counts below 200/µl.
The viral load is a measure of the amount of HIV in the blood. A rising viral load shows that the virus is replicating at a higher rate. The viral load can range from less than 40 virus copies/ml of plasma (below the level of detection of most currently available assays, often called an “undetectable” viral load), to over a million copies/ml.
The course of the illness in untreated people is illustrated by the graph below.
Courtesy of AS Fauci, M.D. Adapted from: Ann Intern Med. 1996 Apr 1; 124(7):654-63.
Primary infection
Between 2 and 6 weeks after exposure to HIV, the majority of people develop a transient, often mild, non-specific illness (also called sero-conversion or acute HIV syndrome). This is caused by high circulating levels of HIV and a fall in the CD4 count. The most common symptoms are:
- fever
- malaise
- joint pain
- rash
- muscle pain
- mouth ulcers
- sore throat.
Most symptoms resolve after 7 to 10 days. In a few people the illness is more severe and may be associated with opportunistic infection, such as pneumonia as the CD4 count falls transiently below 200/µl. Neurological problems such as Guillain - Barré syndrome and Bell’s palsy (facial weakness) may occur. Those with more severe symptoms are more likely to undergo rapid disease progression.
Asymptomatic phase (CD4 count greater than 350/µl)
After the primary infection, the CD4 count usually increases again, but usually to a level below normal. People with a CD4 count greater than 350/µl are usually asymptomatic, although they may have enlarged lymph glands, which they may not be aware of. The length of the asymptomatic phase varies from person to person. In most people it lasts for 6-8 years. In about 5-10% it can last many years and sometimes decades (long-term non-progressors). In a few, there is a rapid fall in the CD4 count and progression to the symptomatic phase within 6 to 12 months.
Symptomatic phase (CD4 count 200-350 /µl)
When the CD4 count falls to less than 350/µl, the person becomes increasingly susceptible to a number of infections. These include:
- pulmonary tuberculosis
- shingles
- pneumococcal pneumonia
- recurrent oral and vaginal candidiasis (thrush) and rarely
- oral hairy leukoplakia, which are white lesions on the side of the tongue caused by the Epstein-Barr virus.
Individuals also become more susceptible to Kaposi’s sarcoma (a malignant condition which usually presents as disfiguring purple to brown - black nodules and patches) and lymphoma.
People may develop intermittent or persistent non-specific constitutional symptoms, which include:
- lethargy
- anorexia
- weight loss
- diarrhoea
- fever
- night sweats.
Advanced phase (CD4 count less than 200/µl (AIDS)
When the CD4 count continues to fall, opportunistic infections and HIV related tumours may develop. AIDS is defined by having a CD4 count of less than 200/µl, and/or the presence of an AIDS defining condition. This is often referred to as “Advanced HIV.”
People with HIV infection are more likely to be infected with other sexually transmitted infections (STIs) and hepatitis B and/or hepatitis C than the normal population. Individuals diagnosed late in the course of the disease may present with two or more AIDS defining illnesses.
Psychiatric problems may occur. Stress is common and depressive illness is more commonly seen in people with HIV infection and is sometimes made worse by some of the drugs used to treat HIV.
