Astrovirus

Astrovirus is a type of virus, which was discovered in 1975 by means of a transmission electron microscope after a diarrheal outbreak in humans. Meanwhile astroviruses could also be isolated from several other species of mammals and are classified as genus Mamastrovirus. Astro viruses that occur in birds such as ducks, chickens and turkeys, are classified as genus Avastrovirus. Astroviruses are nonenveloped icosahedral viruses with a diameter of 28-35 nm and an eponymous characteristic star-shaped surface structure which is visible under an electron microscope. Astroviridae are just like Caliciviridae and Picornaviridae non-enveloped, single-stranded RNA viruses of positive polarity. Human astroviruses have been described as cause of gastroenteritis in children worldwide.

Human astroviruses

Species of Astro viruses are causative agents of gastroenteritis, especially in children but also in adults. Symptoms of infection include diarrhea, vomiting, fever and abdominal pain. The disease takes an average of 3 to 4 days, but is generally not a dangerous situation dar. In rare cases, it may also come to dehydration. Infected do not require inpatient treatment, as the symptoms subside after a short time by itself.

Diagnosis

Electron microscopy, ELISA, immunofluorescence and PCR can be applied in the course of a viral diagnosis to detect virions, antigens or viral RNA in the stool of infected persons.

Epidemiology

A study in the United Kingdom, which was published in 1999, identified a Indizenz of 3.8 per 1000 population per year, which astroviruses are the fourth - most common cause of viral gastroenteritis. Studies in the U.S. have astroviruses in stool of 2 - detected 9 percent of children with corresponding symptoms. The disease is most common in children under 2 years, but there were also outbreaks in adults. Studies from Glasgow and the United States suggest that the infection is often asymptomatic done with astroviruses. In areas with a temperate climate astrovirus infections occur more frequently in winter, while most of the infections occur in the tropics during the rainy season. Astro viruses are transmitted through contaminated water or contaminated food.

Prevention

There is no vaccine or antiviral treatment against astroviruses, the risk of infection, however, can be reduced by personal hygiene.

Genome

The genome of the virus consists of an Astro single-stranded RNA of positive polarity, and has a poly -A tail at the 3'- end but not the 5'- cap structure. Without the poly -A tail, the genome of astroviruses is 6.8 to 7.9 kbp long. It contains three open reading frames, with ORF1a and ORF1b by 70 bp overlap. The third open reading frame is called ORF2. As a mutation rate of 3.7 × 10-3 nucleotide substitutions per site and year and a synonymous change rate of 2.8 × 10-3 nucleotide substitutions per site and year were determined.

Host range

The known host range (synonym tropism ) of astroviruses includes humans, goats, cattle, sheep, pigs, deer, bats, and sea lions.

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