But obligate anaerobe, only grows when oxygen not available. Viruses are found in all 5 Kingdoms. In either case, can take over a host cell. Characteristic of cells with cell wall, which must be broken open for virus release to occur. Characteristic of animal cells with no cell wall.
Some viruses go into a non-replicating stage inside host cell.
They may remain dormant for years, suddenly erupt back into lytic or shedding cycle as a result of stress. The most common of all infectious diseases. Over 200 different viruses may cause cold. Most are RNA viruses in rhinovirus family. Reproduce best at temperatures cooler than body temp.