Which agent requires a host to survive?

Which agent requires a host to survive?

• A. Anthrax
• B. Small pox
• C. Botulinum toxin
• D. Plague

Answer: (B)

Some infectious agents cannot maintain themselves outside living cells; they are obligate intracellular parasites. Viruses rely entirely on a host cell to reproduce, so they must have a living host to survive and spread. The smallpox virus fits this idea because it cannot replicate or persist without infecting human cells; its life cycle depends on a living host, with no environmental reservoir capable of sustaining it on its own. In contrast, anthrax can form hardy spores that survive in soil for long periods and outlast many environments; botulinum toxin remains stable in contaminated food and settings; plague bacteria can persist in animal reservoirs and environmental niches. These differences mean they don’t require a living host in the same way a virus does.

Some infectious agents cannot maintain themselves outside living cells; they are obligate intracellular parasites. Viruses rely entirely on a host cell to reproduce, so they must have a living host to survive and spread. The smallpox virus fits this idea because it cannot replicate or persist without infecting human cells; its life cycle depends on a living host, with no environmental reservoir capable of sustaining it on its own.

In contrast, anthrax can form hardy spores that survive in soil for long periods and outlast many environments; botulinum toxin remains stable in contaminated food and settings; plague bacteria can persist in animal reservoirs and environmental niches. These differences mean they don’t require a living host in the same way a virus does.