Question

Which virus is NOT sensitive to disinfection of water by chlorination?

• A. Rotavirus
• B. Norwalk virus
• C. Poliovirus
• D. None

Hint:

Think of the non-enveloped enteric viruses that survive routine chlorine, the same group as hepatitis A and E.

Answer 1

The Correct Option is C

Step 1: The question tests which waterborne virus survives ordinary chlorine disinfection. Chlorine sanitises drinking water effectively against vegetative bacteria but spares a defined group of resistant organisms.

Step 2: Organisms that escape routine chlorine doses include Entamoeba histolytica cysts, bacterial spores, and the hardy enteric viruses, chiefly poliovirus and the hepatitis A and E viruses.

Step 3: Why poliovirus survives: its non-enveloped, tightly packed protein capsid resists oxidative damage from hypochlorous acid at the concentrations normally used for municipal water.

Step 4: Rotavirus and Norwalk (norovirus) are listed as distractors, but the textbook-recognised chlorine-resistant virus in this set is poliovirus.

\[\boxed{\text{Poliovirus}}\]