Why do viruses not increase in number while in wastewater?

Viruses rely on a host cell to reproduce because they are not capable of cellular metabolism on their own. Unlike bacteria and other microorganisms that can divide and multiply independently in a suitable environment, viruses must invade the cells of living organisms to replicate. In wastewater, while viruses may persist for some time, they cannot increase in number unless they find a suitable host. Therefore, their replication is entirely dependent on the presence of host cells, which are typically not available in wastewater. This explains why viruses do not increase in number while present in this environment.

The other options are not accurate; for instance, while treatment processes can eliminate some viruses, this does not address why they do not replicate in wastewater. Similarly, viruses can survive in water for varying durations, and they do not reproduce asexually as they are reliant on hosts for their propagation.