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Rotavirus
Rotaviruses are
classified with 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 serological 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.
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.
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More
About Rotavirus
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Rotavirus
is the most common cause of severe diarrhea among children,
resulting in the hospitalization of approximately 55,000 children each
year in the United States and the death of over 600,000 children
annually worldwide. The incubation period for rotavirus disease is
approximately 2 days. The disease is characterized by vomiting and
watery diarrhea for 3 - 8 days, and fever and abdominal pain occur
frequently. Immunity after infection is incomplete, but repeat
infections tend to be less severe than the original infection.
Rotavirus is very contagious; it spreads when infants or young children
come into contact with an infected person or objects contaminated by
the feces of an infected person.
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.
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