First off, a virus is simple. In fact, viruses are generally considered the most primitive cellular infectious agents. They’re tiny and easily pass through barriers.Viruses are also easily transmitted from one host to the next. When this happens, they stand on their own in their ability to infect the new host without many other dependent conditions.
Lastly, viruses are effective in small doses. For example, just a cough, sneeze or a short conversation can spread the flu virus to someone up to six feet away.
