Answer:
When a virus enters a host cell, it can reproduce either by the lytic or the lysogenic cycle.
In the lytic cycle, the virus genome enters the genome of the host cell and transcribe and translate. As a result, excess virus structures are formed which cause the host cell to break.
During the lysogenic cycle, the virus gets incorporated into the host genome. Its DNA or RNA is replicated but not translated. Hence, in such a situation the virus can remain in the body for many years without showing any signs or symptoms. After years, it might start to translate and hence the occurrence of the disease is then known.
