There are more than 200 different viruses that cause the common cold. The incubation period depends on the kind of viral infection; the average incubation period is two or three days.
Even a single virus particle affecting a single cell can cause a viral infection. The virus particle starts reproducing and once the infected cell dies, the virus spreads to other cells.
According to the National Institute of Allergy and Infectious Diseases, the rhinovirus accounts for 30 per cent to 50 per cent of all cases of the common cold. It has a typical incubation period of 10 to 12 hours. In contrast, the influenza virus has an incubation period of one day to a week.
The symptoms of the common cold worsen over two to three days. After this time the immune system starts fighting the virus by producing more white cells, but symptoms can linger for two to three weeks.
The immune system also produces antibodies to the virus, which prevent future infections by the same virus, but not other viruses.
The different viruses that cause the common cold include adenovirus, coronavirus, enteroviruses, influenza virus, rhinovirus, metapneumovirus, respiratory syncytial virus and parainfluenza.