The smallest known types of infectious agent. It is debatable whether viruses are truly living organisms or just collections of molecules capable of selfreplication under specific conditions. Their sole activity is to invade the cells of other organisms, which they then take over to make copies of themselves. Outside living cells, viruses are inert.
A single virus particle (virion) consists of an inner core of nucleic acid, which may be either DNA or RNA, surrounded
by 1 or 2 protective protein shells (capsids). Surrounding the outer capsid may be another layer, the viral envelope, which consists mainly of protein. The nucleic acid consists of a string of genes that contain coded instructions for making copies of the virus.
Common viral diseases include the common cold, influenza, and chickenpox (caused by the varicella–zoster virus). AIDS is caused by the human immunodeficiency virus (HIV).
A group of viruses so-called because they were ?rst isolated from two patients with a disease resembling paralytic POLIOMYELITIS, in the village of Coxsackie in New York State. Thirty distinct types have now been identi?ed. They constitute one of the three groups of viruses included in the family of ENTEROVIRUSES, and are divided into two groups: A and B. Despite the large number of types of group A virus (24) in existence, evidence of their role in causing human disease is limited. Some, however, cause aseptic MENINGITIS, non-specicifc upper respiratory infection and MYOCARDITIS, and others cause a condition known as HERPANGINA. HAND, FOOT AND MOUTH DISEASE is another disease caused by the A group. All six types of group B virus have been associated with outbreaks of aseptic meningitis, and they are also the cause of BORNHOLM DISEASE. Epidemics of type B2 infections tend to occur in alternate years. (See VIRUS.)... coxsackie viruses
The most common causes of viral hepatitis are those caused by the Hepatitis A, B, C, D, E and G viruses. Hepatitis F virus has been described but is a doubtful entity. Other viruses which can cause hepatitis include the Epstein-Barr Virus, cytomegalovirus, and the Yellow Fever virus.... hepatitis viruses
One member of a group of viruses containing DNA which cause latent infections in animals and humans. Viruses from this group cause HERPES SIMPLEX, HERPES ZOSTER (shingles) and CHICKENPOX, and include CYTOMEGALOVIRUS (CCMV) and EPSTEIN-BARR VIRUS.... herpes viruses
These include the human papilloma viruses (HPV), of which nearly a hundred strains have been identi?ed. HPV cause verrucae (see WARTS) on skin and, less often, on the mucous membranes of mouth, larynx, genitalia and the cervix. Some strains may predispose to eventual cancer.... papova viruses
These are included in the paramyxoviruses (see MYXOVIRUSES) and divided into four types, all of which cause infection of the respiratory system (see RESPIRATION). Infection with type 3 begins in May, reaches a maximum in July or August and returns to base-line level in October. Types 1 and 2 are predominantly winter viruses. Children are commonly affected and the manifestations include CROUP, fever, and a rash.... parainfluenza viruses
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