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Rotaviruses

Author: Wikipedia, Posted on Tuesday, September 14 @ 15:02:48 IST by RxPG  

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Microbiology


Scientific classification

dsRNA viruses
Family: Reoviridae
Genus: Rotavirus

Species
Rotavirus A (RV-A)
Rotavirus B (RV-B)
Rotavirus C (RV-C)
Rotavirus D (RV-D)
Rotavirus E (RV-E)

Rotaviruses are a genus of viruses belonging to the Reoviridae family. They have a genome consisting of 11 double-stranded RNA segments surrounded by a distinctive two-layered protein capsid. Particles are 70 nm in diameter and have a buoyant density of 1.36 g/ml in CsCl. Six antigenic groups have been identified, three of which (groups A, B, and C) infect humans.

Nature of Acute Disease
Rotaviruses cause acute gastroenteritis. Infantile diarrhea, winter diarrhea, acute nonbacterial infectious gastroenteritis, and acute viral gastroenteritis are names applied to the infection caused by the most common and widespread group A rotavirus. The virus is more commonly known as the Stomach Flu, although it shares no resemblance to an actual flu.


Nature of Disease
Rotavirus gastroenteritis is a self-limiting, mild to severe disease characterized by vomiting, watery diarrhea, and low-grade fever. The infective dose is presumed to be 10-100 infectious viral particles. Because a person with rotavirus diarrhea often excretes large numbers of virus (108-1010 infectious particles/ml of feces), infection doses can be readily acquired through contaminated hands, objects, or utensils. Asymptomatic rotavirus excretion has been well documented and may play a role in perpetuating endemic disease.


Diagnosis of Human Illness
Specific diagnosis of the disease is made by identification of the virus in the patient's stool. Enzyme immunoassay (EIA) is the test most widely used to screen clinical specimens, and several commercial kits are available for group A rotavirus. Electron microscopy (EM) and polyacrylamide gel electrophoresis (PAGE) are used in some laboratories in addition or as an alternative to EIA. A reverse transcription-polymerase chain reaction (RT-PCR) has been developed to detect and identify all three groups of human rotaviruses.


Associated Foods
Rotaviruses are transmitted by the fecal-oral route. Person-to-person spread through contaminated hands is probably the most important means by which rotaviruses are transmitted in close communities such as pediatric and geriatric wards, day care centers and family homes. Infected food handlers may contaminate foods that require handling and no further cooking, such as salads, fruits, and hors d'oeuvres. Rotaviruses are quite stable in the environment and have been found in estuary samples at levels as high as 1-5 infectious particles/gal. Sanitary measures adequate for bacteria and parasites seem to be ineffective in endemic control of rotavirus, as similar incidence of rotavirus infection is observed in countries with both high and low health standards.


Relative Frequency of Disease
Group A rotavirus is endemic worldwide. It is the leading cause of severe diarrhea among infants and children, and accounts for about half of the cases requiring hospitalization. Over 3 million cases of rotavirus gastroenteritis occur annually in the U.S. In temperate areas, it occurs primarily in the winter, but in the tropics it occurs throughout the year. The number attributable to food contamination is unknown.

Group B rotavirus, also called adult diarrhea rotavirus or ADRV, has caused major epidemics of severe diarrhea affecting thousands of persons of all ages in China.

Group C rotavirus has been associated with rare and sporadic cases of diarrhea in children in many countries. However, the first outbreaks were reported from Japan and England.


Course of Disease and Complications
The incubation period ranges from 1-3 days. Symptoms often start with vomiting followed by 4-8 days of diarrhea. Temporary lactose intolerance may occur. Recovery is usually complete. However, severe diarrhea without fluid and electrolyte replacement may result in death. Childhood mortality caused by rotavirus is relatively low in the U.S., with an estimated 100 cases/year, but reaches almost 1 million cases/year worldwide. Association with other enteric pathogens may play a role in the severity of the disease.


Target Populations
Humans of all ages are susceptible to rotavirus infection. Children 6 months to 2 years of age, premature infants, the elderly, and the immunocompromised are particularly prone to more severe symptoms caused by infection with group A rotavirus.


Food Analysis
The virus has not been isolated from any food associated with an outbreak, and no satisfactory method is available for routine analysis of food. However, it should be possible to apply procedures that have been used to detect the virus in water and in clinical specimens, such as enzyme immunoassays, gene probing, and PCR amplification to food analysis.


Selected Outbreaks
Literature references can be found at the links below.

MMWR 48(27):1999 On August 31, 1998, a tetravalent rhesus-based rotavirus vaccine (RotaShield[Registered]*, Wyeth Laboratories, Inc., Marietta, Pennsylvania) (RRV-TV) was licensed in the United States for vaccination of infants. The Advisory Committee on Immunization Practices (ACIP), the American Academy of Pediatrics, and the American Academy of Family Physicians have recommended routine use of RRV-TV for vaccination of healthy infants (1,2). During September 1, 1998-July 7, 1999, 15 cases of intussusception (a bowel obstruction in which one segment of bowel becomes enfolded within another segment) among infants who had received RRV-TV were reported to the Vaccine Adverse Event Reporting System (VAERS).

Outbreaks of group A rotavirus diarrhea are common among hospitalized infants, young children attending day care centers, and elder persons in nursing homes. Among adults, multiple foods served in banquets were implicated in 2 outbreaks. An outbreak due to contaminated municipal water occurred in Colorado, 1981.

Several large outbreaks of group B rotavirus involving millions of persons as a result of sewage contamination of drinking water supplies have occurred in China since 1982. Although to date outbreaks caused by group B rotavirus have been confined to mainland China, seroepidemiological surveys have indicated lack of immunity to this group of virus in the U.S.

The newly recognized group C rotavirus has been implicated in rare and isolated cases of gastroenteritis. However, it was associated with three outbreaks among school children: one in Japan, 1989, and two in England, 1990.

MMWR 47(45):1998 In August 1998, the first live attenuated rotavirus vaccine (Rotashield{registered} {Wyeth Lederle Vaccines and Pediatrics}) was approved for use in infants by the Food and Drug Administration. The Advisory Committee on Immunization Practices has recommended that this vaccine be given as a three-dose schedule to infants aged 2, 4, and 6 months. Since 1991, rotavirus activity in the United States has been prospectively monitored by the National Respiratory and Enteric Virus Surveillance System (NREVSS), a voluntary, laboratory-based system. This report summarizes surveillance data from NREVSS during the 1997-1998 rotavirus season and reviews issues related to rotavirus surveillance that are important for a national rotavirus vaccine program.

MMWR 47(19):1998 On June 24, 1996, the Livingston County (New York) Department of Health (LCDOH) was notified of a cluster of diarrheal illness following a party on June 22, at which approximately 30 persons had become ill. This report summarizes the findings of the investigation, which implicated a deficient water supply system as the cause of an outbreak of diarrheal illness caused by Salmonella serotype Hartford and P. shigelloides. Unfiltered, untreated surface water led to contamination of food during its preparation.

MMWR 40(5)1991 A discussion of rotavirus surveillance in the US.

The above is based on a page from the public domain Bad Bug Book



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