Viral diseases

Viruses are not alive because they do not complete all of the seven life processes, which are:

  • movement
  • respiration
  • sensitivity
  • nutrition
  • excretion
  • reproduction
  • growth

We say 'strains' of virus and not species. Strains are made of a relatively short length of genetic material (DNA) which is surrounded by a protein coat.

Viral infections cannot be treated by antibiotics.


HIV stands for human immunodeficiency virus. This infection is transmitted by body fluids, often during unprotected sex, but also through cuts and injecting drugs using unsterilized needles. Immediately after infection, people often suffer mild flu-like symptoms. These pass and for a period of time infected people might not know they are infected.

AIDS stands for acquired immune deficiency syndrome. Months or years after the infection by HIV, the virus becomes active and attacks the patient's white blood cells. HIV at this point has resulted in AIDS.

There is no cure for HIV/AIDS although scientists are trying to find one. Currently, infected people are given antiviral drugs, which can significantly slow the development of AIDS.

A map showing the percentage of global population with AIDSPercentage of global population with AIDS


In 2015 an outbreak of Ebola occurred in West Africa. Between 50% and 90% of Ebola cases are fatal. Early symptoms of Ebola include:

  • fever and headache
  • joint and muscle pain
  • muscle weakness

Patients then develop diarrhoea, vomiting, stomach pain and internal bleeding.

The virus is transmitted in body fluids. It is possible to catch it from a dead person several days after they have died. It is also possible to catch it from the clothes or possessions of a dead person, having sex with an infected person or from unsterilized needles shared with an infected person.

There is currently no licensed treatment for Ebola.