Viral infections are caused by a virus. Millions of types of virus are thought to exist, but only 5,000 types have been identified. Viruses contain a small piece of genetic code. They are protected by a coat of protein and fat.
Viruses invade a host and attach themselves to a cell. As they enter the cell, they release genetic material. The genetic material forces the cell to replicate, and the virus multiplies. When the cell dies, it releases new viruses, and these go on to infect new cells.
Not all viruses destroy their host cell. Some of them change the function of the cell. In this way, viruses such as human papillomavirus (HPV) or Epstein-Barr virus (EBV) can lead to cancer by forcing cells to replicate in an uncontrolled way.
They can also target certain age groups, such as infants or young children.
A virus may remain dormant for a period before multiplying again. The person with the virus can appear to have recovered but may get sick again when the virus reactivates.
Here are some examples of viral infections:
- the common cold, mainly caused by the rhinovirus, coronavirus, and adenovirus
- encephalitis and meningitis, caused by enteroviruses and the herpes viruses
- warts and skin infections, caused by the human papillomaviruses (HPV) and herpes simplex virus (HSV).
- gastroenteritis, caused by the novavirus
Other viral conditions include:
- Zika virus
- human immunodeficiency virus (HIV)
- hepatitis C
- polio
- influenza
- Dengue fever
- H1N1 swine flu
- Ebola
- Middle East respiratory syndrome (MERS-CoV)
Antiviral medications help in some cases. They can either prevent the virus from reproducing or boost the host’s immune system.
Antibiotics are not effective against viruses. Using antibiotics against a virus will not stop the virus, and it increases the risk of antibiotic resistance.
Most treatment aims to relieve symptoms while the immune system combats the virus without assistance from medicine.
