Final answer:
The statement that viruses cannot increase in number in wastewater is true since they require a host cell for replication. A new virus can emerge and spread if it evolves to infect a new host species, and there is close contact in a dense population.
Step-by-step explanation:
The statement 'Since viruses require a host cell to reproduce they do not increase in number while in wastewater' is true. Viruses cannot replicate on their own because they lack the necessary cellular machinery needed for replication.
They must infect a host cell and utilize its replication mechanisms to produce new viral particles. Outside of a host, such as in wastewater, viruses are not able to multiply because they do not come into contact with cells that they can infect and use for replication.
In order for a new virus to emerge and spread, several conditions must be met. First, the virus must undergo genetic changes, which can happen through rapid viral reproduction that often produces errors.
These genetic changes might enable the virus to infect a new host species.
Additionally, for the virus to spread effectively, it needs to encounter a suitably large and dense population, and there must be close contact between potential new host organisms, allowing the virus to transfer and establish itself.
The lysogenic cycle is a viral reproductive cycle where the virus integrates its genetic material into the host cell's genome, allowing it to be preserved during unfavorable conditions.
This is different from the lytic cycle, where the virus immediately replicates and causes the destruction of the host cell to release new viruses.