HIV infection can be classified in two ways :
- Four clinical stages based on the presence or absence of signs, symptoms and opportunistic infections. This is more commonly used and is known as the WHO clinical staging of HIV/AIDS for adults and adolescents.
- Three clinical categories of HIV infection which is based on the CD4 T-cell count plus the presence or absence of signs, symptoms and opportunistic infections. This is known as the CDC classification system for HIV infection and is not widely used.
Primary Infection or Acute HIV Infection
This first phase of HIV infection is referred to as the primary infection phase or acute infection phase. It is not categorized as a clinical stage according to the classification systems above. It usually evident within 2 to 6 weeks after infection and can last for 8 to 12 weeks. During this phase, the first signs of HIV may be noticed although up to 30% of new infections may be asymptomatic (no symptoms).
Some of the clinical features of this stage includes :
- Muscle and/or joint pain
- Sore throat
- Swollen lymph nodes
- Mouth ulcers/sores
Asymptomatic HIV Infection
WHO Stage One, CDC Category A
As the name suggests, there is usually no signs or symptoms present in this phase – the first signs of HIV infection (stage one) is no longer evident. However, there may be a persistent generalized lymphadenopathy which :
- lasts for 3 months or more at a time.
- affects two or more sites of the body (other than the inguinal/groin nodes).
- the swollen nodes are usually >1cm in diameter.
This phase can last for 7 to 10 years but it may be longer or shorter depending on a number of factors. The CD4 T-cell count is usually above 500 cells/mm3, however, some patients with a CD4 T-cell count below 500 cells/mm3 but usually above 350 cells/mm3 may also be within this phase.
Mildly Symptomatic Disease or Early Symptomatic HIV Infection
WHO Stage Two and Three, CDC Category B
In this phase of HIV infection, persistent or recurrent symptoms become evident. It is the transition phase between being asymptomatic and the development of AIDS. Persistent signs and symptoms or recurrent conditions include :
- Chronic diarrhea
- Night sweats
- Low grade fever
- Joint pain
- Unintentional weight loss – moderate in stage two (<10% of body weight) or severe (>10%) in stage three
- Oral candidiasis (thrush)
- Vaginal candidiasis
- Mouth ulcers
- Oral hairy leukoplakia
- Herpes zoster (shingles)
- Peripheral neuropathy
- Pelvic inflammatory disease
- Cervical dysplasia
- Fungal skin infections
- Bacterial infections
- Molluscum contagiosum
- Other itchy skin rashes
These stages usually correlate with a CD4 T-cell count less than 500 cells/mm3, however, the CD4 count could be higher in some patients.
AIDS or AIDS-Related Complex (ARC)
WHO Stage Four, CDC Category C
The fourth or final stage of HIV infection is what is termed as AIDS (Acquired Immune Deficiency Syndrome) and this is based on the presence of certain diseases (known as AIDS-defining illnesses) and/or a CD4 T-cell count lower than 200 cells/mm3.
AIDS Defining Illnesses
The conditions listed below do not only occur in AIDS. While these conditions are rare, any immunocompromised patient may be prone to contracting these infections or developing these signs. It should only be considered as an AIDS defining illness once HIV infection has been confirmed. A declining CD4 count and rising viral load will further serve to confirm that these are AIDS defining illnesses.
- Candidiasis (thrush) of the esophagus
- Cerebral lymphoma, primary
- Coccidiodomycosis, extrapulmonary
- Cryptococcal meningitis
- CNS toxoplasmosis
- Cytomegalovirus (CMV) infection (retinitis, colitis and/or other organs)
- Dementia, HIV associated
- Mycobacterium avium intracellulare, disseminated
- Histoplasmosis, extrapulmonary
- Invasive cervical cancer
- Kaposi’s sarcoma
- Leukoencephalopathy, progressive multifocal
- Non-Hodgkin lymphoma
- Pneumocystis pneumonia
- Salmonella bacteremia, recurrent non-typhoidal
- Tuberculosis, pulmonary (lung) or extrapulmonary
- Wasting (cachexia), HIV associated
- First Signs of HIV – Early Infection Symptoms, Risks, Other Cause
- First HIV Test and Meaning of HIV Early Test Results