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Rotavirus

General characteristics

Rotaviruses are classified with the Reoviridae family. Six serological groups have been identified, three of which (groups A, B, and C) infect humans.

Group A rotavirus is endemic worldwide. It is the leading cause of severe diarrhoea among infants and children, and accounts for about half of the cases requiring hospitalisation. 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 diarrhoea rotavirus or ADRV, has caused major epidemics of severe diarrhoea affecting thousands of persons of all ages in China.

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

Disease symptoms

Rotaviruses cause acute gastroenteritis. Infantile diarrhoea, winter diarrhoea, acute nonbacterial infectious gastroenteritis, and acute viral gastroenteritis are names applied to the infection caused by the most common and widespread group A rotavirus.

Rotavirus gastroenteritis is a self-limiting, mild to severe disease characterized by vomiting, watery diarrhoea, and low-grade fever. The infective dose is presumed to be 10-100 infectious viral particles. Because a person with rotavirus diarrhoea often excretes large numbers of virus (108-1010 infectious particles/ml of faeces), 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.

The incubation period ranges from 1-3 days. Symptoms often start with vomiting followed by 4-8 days of diarrhoea. Temporary lactose intolerance may occur. Recovery is usually complete. However, severe diarrhoea without fluid and electrolyte replacement may result in severe diarrhoea and death.

Diagnosis

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/l.

Prevention

The viruses are heat-sensitive and will be killed by thorough heating (over 70 °C).

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.

Risk 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.

Sources:

The bad bug book : http://www.cfsan.fda.gov/~mow/intro.html