Your question does not give enough information. What are "which"? Should there be more to the question?
Multiply. A virus needs energy to multiply.
generally bacteria and viruses multiply rapidly in colder environments rather than hot conditions.so,cold virus need hot
viruses cannot spoil food because they need a host cell(living) to multiply. Food does not provide it a proper ambience or favourable conditions to survive/multiply.(in the atmosphere viruses are said to be dead).
When its host cell makes more copies of the virus
The capsid of the cell helps the virus to infect host cells as well as multiply quickly.
protein
No, a virus cannot catch a virus and become ill. A virus is a shell of protein containing DNA. A virus works by getting into a cell and "reprogramming it" to multiply and start to take of the organism. A virus cannot infect another virus because viruses are not cells themselves.
To insert into a healthy cell so that it can multiply.
virus
multiply
Viruses can only multiply (reproduce) within a host cell. The type of host cell is dependent on the virus' host range.
Yes..... You need an ANTI-VIRUS to do it.