Life cycle of a virus

Diagram showing the life cycle of a virus

The life cycle of a virus is the same as other pathogens. They can often survive outside a host for long periods of time. When they do infect a suitable host cell or cells, they replicate themselves within the cell thousands of times. They do not divide and reproduce like cells, but complete the lytic pathway.

  1. They replicate their DNA and protein coats.
  2. These are then assembled into new virus particles.
  3. This causes the host cell or cells to burst. This is called lysis and provides the name of the 'lytic cycle'.
  4. Other nearby cells can then be infected with the virus. This process can be as quick as twelve hours in the case of the norovirus or several days for the process of Ebola.

Other types of virus called phages either join their DNA to that of their host or leave small circles of their DNA in the cytoplasm of their host cell or cells. This is called the lysogenic pathway. When these cells divide the DNA is copied. Later in the life cycle the viral DNA is copied and the lytic cycle detailed above begins.