Classification & Taxonomy

Classification used to be based only on the host of origin; a new classification scheme has been proposed based on the amino acid sequence of Open Reading Frame 2 (this encodes for the capsid polyprotein & has the most variance in the genome).

Family: Astroviridae, Genera: Avastrovirus, Mamastrovirus

They are single stranded, positive sense RNA viruses and are monopartite

They are nonenveloped

The capsid morphology is icosahedral

They are the second or third most common cause of viral diarrhea in young children.

Have been isolated from humans, pigs, cats, minks, sheep, calfs, dogs, bats, rats, deer, and marine mammals such as dolphins and sea lions (these of the Mamastrovirus). Of the Avastrovirus, the virus has been isolated from ducks, chickens, turkeys, and guinea fowl.

Works Cited

“Human Astroviruses.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 19 Mar. 2015.

Knipe, David M., and Bernard N. Fields. “Chapter 21: Astroviridae.” Fields’ Virology. 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2013. 609-28. Print.

“ViralZone: Astroviridae.” ViralZone: Astroviridae. ExPASy, n.d. Web. 19 Mar. 2015.

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It has T=3 icosahedral symmetry

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The capsid is about 35 nm, spikes protrude from 30 vertices.

The cellular tropism: enterocytes / epithelial cells of the intestinal tract.

Works Cited

“Human Astroviruses.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 19 Mar. 2015.

Knipe, David M., and Bernard N. Fields. “Chapter 21: Astroviridae.” Fields’ Virology. 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2013. 609-28. Print.

“ViralZone: Astroviridae.” ViralZone: Astroviridae. ExPASy, n.d. Web. 19 Mar. 2015.

Molecular Biology

Replication occurs in the cytoplasm

  1. There is attachment to host receptors, which mediates the endocytosis of the virus into host cell.
  2. There is uncoating and subsequent release of the viral genomic RNA into the cytoplasm
  3. The RNA is translated into two polyproteins to create replication proteins, which happens in the Endoplasmic Reticulum (double stranded RNA genome is created from the positive single stranded RNA).
  4. Subgenomic RNA translation creates the capsid precursor
  5. Assembly of the new virions
  6. Maturation of the capsid and non-lytic virus release  http://viralzone.expasy.org/viralzone/all_by_species/27.html

The organization of the astrovirus genome places the Open Reading Frames encoding the structural proteins at the 3’ end and the nonstructural proteins at the 5’ end. Other distinctive features of the family include the lack of a DNA-helicase, and the usage of ribosomal frameshifting as a mechanism to translate the RNA –dependent RNA polymerase.

Works Cited

“Human Astroviruses.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 19 Mar. 2015.

Knipe, David M., and Bernard N. Fields. “Chapter 21: Astroviridae.” Fields’ Virology. 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2013. 609-28. Print.

“ViralZone: Astroviridae.” ViralZone: Astroviridae. ExPASy, n.d. Web. 19 Mar. 2015.

Transmission and Pathogenesis

The transmission is fecal-oral. This means it is transmitted via contaminated water and food, as well as through person to person contact (seen in an outbreak of gastroenteritis in California). Illnesses in adults can also happen as a result of a large exposure to astrovirus or through fomites.

It is partially resistant to chlorination, which is widely used for wastewater treatment in many countries.

Works Cited

“Human Astroviruses.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 19 Mar. 2015.

Knipe, David M., and Bernard N. Fields. “Chapter 21: Astroviridae.” Fields’ Virology. 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2013. 609-28. Print.

“ViralZone: Astroviridae.” ViralZone: Astroviridae. ExPASy, n.d. Web. 19 Mar. 2015.

Clinical Profile

Most astrovirus infections in humans are detected in the winter months (in temperate regions) and in the rainy season (in tropical climates).

Incubation period: 3-4 days

Associated diseases: gastroenteritis, celiac disease, intussusception (Fields 622).

Symptoms: diarrhea in 72% – 100% in all cases, duration from 2-3 days

Abdominal pain: 50%

Vomiting: 20% – 70%

Fever : 20% -25%

Maximum fever: 37.9 ºC

Hospitalization: 6%, duration of 6 days on average

Works Cited

“Human Astroviruses.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 19 Mar. 2015.

Knipe, David M., and Bernard N. Fields. “Chapter 21: Astroviridae.” Fields’ Virology. 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2013. 609-28. Print.

“ViralZone: Astroviridae.” ViralZone: Astroviridae. ExPASy, n.d. Web. 19 Mar. 2015.

Treatment & Diagnostic Tools

Treatment: ; astrovirus usually results in a self-limiting illness that does not require hospitalization. Oral (or intravenous) Rehydration Therapy may be necessary. IVIV may also help in those with immunocompromisation.

Diagnostic tools: Enzyme Immuno-Assay (EIA), electron microscopy, and reverse transcription-polymerase chain reaction (RT-PCR).

Works Cited

“Human Astroviruses.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 19 Mar. 2015.

Knipe, David M., and Bernard N. Fields. “Chapter 21: Astroviridae.” Fields’ Virology. 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2013. 609-28. Print.

“ViralZone: Astroviridae.” ViralZone: Astroviridae. ExPASy, n.d. Web. 19 Mar. 2015.