Infections can also be caused by viruses. Describe the lytic pathway of a virus and how this causes the spread of infection through a population.

Infections can be caused by a variety of different microorganisms. Amongst them, pathogenic viruses can cause a range of different condition, such as the common cold (the flu virus) and the HIV virus. Viruses cannot live outside of a host, upon contact however - the virus can bind and enter the cells of the host. Upon entry, the virus inserts it's own genetic information into the genome of the host cell. Through normal mechanisms of genetic expression the host cell inadvertently produces viral mRNA (since the viral genome has been incorporated into the host cell). The produced viral mRNA is then used to create viral proteins - it is this 'hijacking' of host cell organelles that results in the replication of the virus. These viruses can then go on to infect adjacent host cells in the infected tissue - causing the pathogenesis and development of disease. In addition to this, the production of viral proteins and viruses themselves can result in the lysis of the host cell. When the host cell lyses (bursts) - this can cause the release of viruses and additional viral particles/proteins to permeate through tissues of the body. After the infection process, viral particles can leave the host and go on to infect other individuals. For example, during viral lung infection (e.g. viral pneumonia) viral particles can be found in the mucus of the lungs, and when the infected individual coughs or sneezes, viral particle are dispersed in expelled aerosol and cause the spread of the viral proteins. In addition to this, viruses that manifest in the blood of the host, can infect others through blood-to-blood contact. This is why health care professionals must protect themselves through quarantine and hygiene protocols to prevent the spread of infection.