Class 12 Biology Human Health Disease AIDS


The term AIDS stands for Acquired Immuno Deficiency Syndrome.

The disease is acquired during life time.

AIDS is caused by human immune deficiency virus (HIV).

HIV is a retrovirus having RNA as the genetic material.

Mode of transmission-

  • Sexual contact with infected persons.
  • Bytransfusion of contaminated blood and blood products.
  • By sharinginfected needles as in the case of intravenous drug abusers.
  • From infected mother to her child through placenta.

Life cycle of HIV

  • After getting into the body the virus enters into macrophages or T-helper cells.
  • The viral RNA genome replicated to form viral DNA with the enzyme called reverse transcriptase.
  • The viral DNA gets incorporated into the host cell’s DNA and directs the infected cells to produce virus particles and the macrophages continue to produce virus.
  • Viruses released from macrophages attack T-helper cells and cause a progressive reduction in the number of T-helper cells and due to which the person starts suffering from infections with several other microorganisms.

Diagnosed by ELISA (enzyme linked immune-sorbent assay).

Treated with anti-retroviral drugs but that is only partially effective.

Prevention of AIDS-

  • To follow safe blood transfusion.
  • To use disposable needles.
  • To distribute free condoms.
  • To prevent drug abuse.

Fig. HIV virus  

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