Q.61 Which one of the following is a contagious disease?
(A) Chickenpox
(B) Tetanus
(C) Malaria
(D) Filariasis
Chickenpox is the only contagious disease among the options, as it spreads directly from person to person via airborne transmission. This MCQ tests knowledge of disease transmission modes in biology and microbiology.
Correct Answer
The correct option is (A) Chickenpox. Chickenpox, caused by the varicella-zoster virus, qualifies as a contagious disease because it transmits easily through respiratory droplets, direct contact with rash fluid, or airborne particles from coughing and sneezing.
Option Explanations
Contagious diseases spread from one person to another, unlike non-contagious ones acquired from environmental sources or vectors.
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(A) Chickenpox: Highly contagious viral infection with an R0 (reproduction number) of 8-12, meaning one infected person can spread it to many others before symptoms appear. It spreads via air or contact, making it a classic example in epidemiology.
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(B) Tetanus: Not contagious; caused by Clostridium tetani spores entering wounds from soil or rust, with no person-to-person transmission. The World Health Organization confirms tetanus cannot spread between humans.
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(C) Malaria: Vector-borne, transmitted by Anopheles mosquitoes carrying Plasmodium parasites, not directly from person to person. Human-to-human spread requires the mosquito intermediary.
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(D) Filariasis: Also vector-borne, spread by Culex mosquitoes carrying filarial worms like Wuchereria bancrofti. Direct contagion does not occur.
Why Chickenpox Stands Out
Chickenpox’s high contagiousness leads to outbreaks in unvaccinated populations, preventable by the varicella vaccine. Unlike tetanus (bacterial toxin from wounds), malaria, and filariasis (parasitic, mosquito-transmitted), chickenpox relies on human proximity for spread, fitting the contagious definition perfectly.
