Human Health and Disease — Part 3: AIDS, cancer, and drugs and alcohol: visual lesson, CBSE Class 12 Biology

Lesson

AIDS, cancer, drugs and alcohol

Part 3 — two major diseases and a major social health problem, with the science needed to prevent them.

In this lesson you will

Explain how HIV is transmitted and how it causes AIDS, and how AIDS is prevented
Explain how cancer arises, its causes, detection and treatment
Describe the effects of drug and alcohol abuse, especially in adolescence
Suggest ways to prevent drug and alcohol abuse

Concept

HIV and its spread

AIDS (Acquired Immuno Deficiency Syndrome), first reported in 1981, is caused by HIV, a retrovirus with an RNA genome. There is usually a gap of 5–10 years between infection and symptoms.

Table of ways HIV does and does not spread
HIV spreads by	HIV does not spread by
Sexual contact with an infected person	Touching, hugging or shaking hands
Transfusion of contaminated blood or blood products	Sharing food, water or a classroom
Sharing infected needles	Mosquito bites
Infected mother to child through the placenta	Coughing or sneezing

Concept

How HIV causes AIDS

HIV enters macrophages, where its RNA is copied into viral DNA by reverse transcriptase. The viral DNA joins the host DNA, so infected cells produce new viruses: the macrophage becomes an HIV factory. HIV then enters helper T-lymphocytes, multiplies, and destroys them.

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