Basic Information on HIV/AIDS


Infectious Agent:

Human Immunodeficiency Virus (HIV)

Mode of transmission:

Sexual intercourse (vaginal or anal) with an infected partner, especially in presence of a concurrent ulcerative or non-ulcerative sexually transmitted infection (STI); or
Contaminated needles (injecting drug users, needle-stick injuries, injections),
Transfusion of infected blood or blood products; or
Infected mother to her child during pregnancy, labour and delivery or through breast-feeding.

Incubation period:

May be variable. On an average, time from HIV infection to clinical AIDS is 8 to 10 years, though AIDS may be manifested in less than 2 years or be delayed in onset beyond 10 years. Incubation times are shortened in resource poor settings and in older patients. They can be prolonged by provision of primary prophylaxis for opportunistic infections or anti-retroviral treatment.

Case Definition:

Suspected case:
Not applicable. Note: Sentinel sites should focus on testing high risk groups which include patients seeking treatment for sexually transmitted diseases, users of intravenous drugs, commercial sex workers seeking health treatment, etc. Cases suspected at first level care facility should be referred to second level care facility for confirmation.

Confirmed case:
In 1997, UNAIDS and WHO issued revised recommendations for the selection and use of HIV antibody tests. For diagnosis of HIV infection following strategy is used

If the sample is reactive with the first assay (A), test with second assay (B).
If it is non reactive with the second assay, consider it to be “Indeterminate”.
If serum is reactive in the second assay, test with the third assay (C).
If non-reactive in the third assay, consider it to be “Indeterminate”.
If the serum is reactive in the third assay, report it to be HIV antibody positive.


In case of a confirmed case with HIV infection or AIDS, he/she should receive counseling and be referred to tertiary level care facility for treatment of virus and opportunistic infections such as TB and for follow up.


Primary Prevention:
Prior to development of HIV infection, prevention focuses on modifying the risk behaviors of persons in the community through “behaviour change communication” (BCC).

Secondary Prevention:
Counseling: HIV Positive individuals must be counseled to lead as normal a life as possible, but to take strict precautions regarding sexual intercourse, disposal of used needles and other sharps, and avoiding donating blood. Family and social contacts must be reassured that the infection does not spread by casual contact.


Image courtesy of CDC/ Maureen Metcalfe, Tom Hodge