HIV and AIDS
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Direct answer
AIDS, the Acquired Immuno Deficiency Syndrome, is caused by the Human Immunodeficiency Virus (HIV), a retrovirus with an RNA genome that replicates by making a DNA copy of itself using the enzyme reverse transcriptase. HIV selectively infects helper T-lymphocytes, the cells that orchestrate immune responses, so their gradual loss leaves the patient defenceless against infections that a healthy person would easily resist. The virus spreads through sexual contact, contaminated blood and needles, and from an infected mother to her foetus, and infection is detected by ELISA.
What you must remember
- The virus: HIV is a retrovirus — its genetic material is RNA, and reverse transcriptase converts it into DNA, which then integrates into the host cell's machinery to produce new virus particles.
- The target: helper T-lymphocytes (and macrophages), whose destruction progressively cripples cell-mediated immunity.
- Diagnostic test: ELISA (enzyme-linked immunosorbent assay), the standard screening test for HIV infection.
- Routes of transmission: sexual intercourse with an infected person, transfusion of contaminated blood, reuse of contaminated needles and syringes, and placental transfer from infected mother to foetus.
- Not transmitted by: ordinary touch, hugging, sharing towels or utensils, mosquito and insect bites, or breathing the same air — casual contact carries no risk.
- Consequence of infection: the immune-deficient person falls prey to opportunistic infections by organisms such as Mycobacterium, viruses and fungi, which eventually prove fatal.
- Prevention: screening all donated blood, using disposable or properly sterilised needles, practising safe sex, and nationwide awareness campaigns run by agencies such as NACO.
Common confusion
Being HIV-positive is not the same as having AIDS — infection precedes the immune collapse by years, during which the carrier can look and feel well yet transmit the virus. Students also wrongly fear casual contact and insect bites as routes of transmission. Remember the diagnostic pair: ELISA screens for the virus or antibodies against it, while the Widal test belongs to typhoid.
Exam-focused takeaway
NEET-UG asks the viral group (retrovirus), the enzyme of replication (reverse transcriptase), the cells attacked (helper T-lymphocytes) and the diagnostic test (ELISA). Statement questions list transmission routes versus non-routes, and assertion-reason stems test why opportunistic infections, not HIV itself, usually cause death. India's NACO and awareness-based prevention also appear as single-fact questions.
Frequently asked questions
What causes AIDS?
The Human Immunodeficiency Virus, a retrovirus whose RNA genome is copied into DNA by reverse transcriptase inside host cells.
Which cells does HIV destroy?
Helper T-lymphocytes, whose loss disables the immune system and invites opportunistic infections.
How is HIV transmitted?
Through sexual contact, transfusion of contaminated blood, contaminated needles and syringes, and from an infected mother across the placenta to the foetus.
How is HIV infection diagnosed?
By ELISA, the enzyme-linked immunosorbent assay, used as the standard screening test.
Can HIV spread by casual contact?
No — touching, hugging, sharing food or utensils, insect bites and aerosols do not transmit the virus.