Disease
Astovirus Infections
Author
Michele Stedding, BIOL 230, Spring 2009
Causative Agents
Astroviruses are non-enveloped, single-stranded RNA viruses with an icosahedral (def) capsid. They are small, round shaped viruses approximately 28-30 nanometers in diameter. They have a star-like appearance under an electron microscope. Astroviruses are members of the Astroviridae family and infect both mammalian and avian hosts. To date, there are 8 human serotypes (def) of Astrovirus: HAstV-1 to HAstV-8
Epidemiology
Human Astrovirus infections are endemic in nature with worldwide distribution. They are one of the foremost causes of infantile viral gastroenteritis (def) with serotype 1 (HAstV-1) being the most common virus found in children. Serotypes variation seems to differ by geographical area with Serotype 1 being the most common. Serotypes 2, 3, 4 and 5 are less common. Serotypes 6, 7, and 8 are seldom detected.
Human Astrovirus has been recognized as the second most common cause of diarrhea among children less than five years of age. Studies in the USA have detected Astroviruses in stool samples of 2-9% of symptomatic children. Higher percentages have been noted in developing countries.
Although, the disease primarily affects infant children under the age of two, adults, elderly and immunocompromised individuals are susceptible as well. Outbreaks have occurred in hospitals, daycares and military institutes. Higher incidents of Human Astrovirus infections are noted throughout the winter in temperate climates and during the wet season in tropical climates.
Transmission
Astroviruses common mode of transmission is via the fecal to oral route. This virus is resistant to desiccation (def) and can survive for extended periods of time on inert surfaces. Contaminated water and food have occasionally been implicated as the cause of Astrovirus outbreaks.
Signs and Symptoms
All human Astrovirus Serotypes causes gastroenteritis. Symptoms typically appear 1-4 days after inoculation with duration of 2-3 days. Gastroenteritis symptoms include abdominal pain, cramping, diarrhea, vomiting, headache, nausea, and fever. Dehydration can occur due to excessive fluid loss in relation to diarrhea, vomiting, and excessive sweating. Prolonged dehydration associated with severe infections is uncommon but has been noted. Hospitalization is rare occurring in less than six percent of patients. Human Astrovirus infections are typically mild and self-limiting. Asymptomatic infections do exist. Rare cases of death have been noted.
Prevention and Treatment
There is currently no vaccine for Human Astrovirus infections. By the age of 5, the majority of children have acquired Astrovirus antibodies, providing protection throughout their adult life. Antiviral therapies do not exist. Prevention is aimed at reducing the transmission of the disease. Frequent hand washing and proper food handling techniques can dramatically decrease the transmission rate. The primary goal in treatment is to prevent dehydration by maintaining adequate fluid intake. Intravenous fluids may be administered in severe cases of dehydration.
Bibliography
Guix S, Bosch A, Pinto RM. Human astrovirus diagnosis and typing: current and future prospects. Lett Appl Microbiol. 2005;41:103–105. doi: 10.1111/j.1472-765X.2005.01759.x.
ICTVdB, The Universal Virus Database, version 4, http://www.ncbi.nlm.nih.gov/ICTVdB/ICTVdB
Moser, Lindsey A., and And Stacey Schultz-Cherry. "Suppression of Astrovirus Replication by an ERK1/2 Inhibitor." Journal of Virology, Aug 2008 Vol 82 No 15: pp7475-482. 18 Apr. 2009 http://jvi.asm.org/cgi/content/full/82/15/7475
Kelly, Laura A. Stacey Schultz-Cherry, Spencer V. Muse, and Matthew D. Koci. “Genomic Analysis of Closely Related Astroviruses.” Journal of Virology May 2008 Vol 82 No 10: pp 5099–5103. 18 Apr. 2009 http://jvi.asm.org/cgi/content/abstract/82/10/5099
Koci, Matthew D., Lindsey A. Moser, Laura A. Kelley3 Diane Larsen, Corrie C. Brown, and Stacey Schultz-Cherry “ Astrovirus Induces Diarrhea in the Absence of Inflammation and Cell Death.” Journal of Virology, Nov 2003, Vol. 77: pp. 11798-11808. American Society for Microbiology. 18 Apr. 2009 http://jvi.asm.org/cgi/content/full/77/21/11798