A Major Cause of Childhood Morbidity and Mortality
Kelly A. Reynolds, Ph.D.
Rotavirus is a pathogen of the
gastrointestinal tract that causes severe acute gastroenteritis
and diarrhea among infants and children, and is the most common
cause of severe vomiting and diarrhea in children worldwide. Rotavirus
is capable of long term survival and infections are highly contagious.
Although repeat infections appear to be less severe, children may
become infected several times with rotavirus.
The virus has a characteristic
wheel and spoke shape and shares a number of features with the influenza
virus. With a wide variety of types and subtypes of the virus group-and
the ability to change their surface proteins over time-a number
of different rotaviruses may be present in communities at the same
time. In addition, like influenza infections, rotavirus illness
has a seasonal fluctuation, with infections in North America peaking
in the winter.
There are six distinct
serological groups of the virus, labeled A through F. Group A rotaviruses
typically cause infections in humans; and also primates, horses,
pigs, dogs, cats, rabbits, mice, cattle and birds. Other groups
infect pigs (B, C, E), cattle (B), sheep (B), rats (B), ferrets
(C), and chicken (D, F, G). Groups B and C rotaviruses have been
known to cause infections in humans, and may be associated with
transfer of the pathogen from their animal hosts.
Public health impact
Enteric illness continues to be a rampant problem worldwide resulting
in significant morbidity and mortality. Officials estimate that
by the age of four, nearly every child will have been infected with
rotavirus. Sadly, more than 870,000 deaths throughout the world
each year are due to rotaviral gastroenteritis. Death is usually
due to severe dehydration and loss of electrolytes, treatable symptoms
in regions with access to medical supplies and clean water. Although
3.5 million cases of rotaviral diarrhea are estimated to occur yearly
in the U.S., the death rate is much lower than in developing countries,
with up to 125 deaths and 104,000 hospitalizations. In the United
States, it's estimated that rotavirus illness costs in excess of
$1.4 billion per year.
Marked by vomiting,
high fever, and diarrhea, rotavirus illness typically manifests
after 12 hours to four days of exposure and lasts from 4-to-8 days.
Humans of all ages are susceptible to rotavirus infections; however,
children under age two and the immunocompromised are more likely
to experience severe symptoms from the infection.
Many rotavirus infections may not result in noticeable disease symptoms,
and are thus termed asymptomatic. Spread by the fecal-oral route,
an infected person may excrete up to 10 billion viruses per gram
of feces, providing a source for water contamination via sewage
or fomites (inanimate objects) and food contamination via tainted
hands. Waterborne outbreaks of rotavirus have been recorded and
rotavirus continues to be found in sewage, source waters and shellfish
harvest areas. One study found rotavirus present in 20 percent of
the shellfish in the test area. What's more alarming is that no
relationship was found between viral contamination and bacterial
indicators-the routine test to determine the overall water quality.
As mentioned, rotavirus
may also be transmitted by air, hands, fomites and food. Known to
survive for weeks in potable and recreational waters, and for at
least four hours on human hands, the potential for cross-contamination
to other surfaces and unsuspecting individuals is high. Outbreaks
are common in childcare centers and in pediatric hospitals and have
been documented in elderly nursing homes. In January 1989, the Centers
for Disease Control (CDC) established a National Rotavirus Surveillance
System in the United States to monitor the presence of rotavirus.
During the 23-month survey period, rotavirus was detected in 20
percent of 48,035 specimens from pediatric, community, commercial,
hospital and public health laboratories. A similar survey conducted
in 1998 revealed an incidence rate of 23 percent in 22,912 fecal
Typical of many virus infections, there's no treatment for rotaviral
gastroenteritis other than supportive therapy. Keeping the patient
hydrated either by intravenous fluids or oral rehydration (electrolyte
replacement) formulas drastically reduces the chance for death by
dehydration. Although nursing babies may still become infected,
asymptomatic infection is more likely in the first three months
of life due to the passive immunity of transplacental antibodies
and human breast milk.
According to the results
of a new study, rotavirus may cause symptoms by stimulating the
nervous system in the wall of the gut, leading to increased secretion
of salts and water. Targeting the mechanism of rotavirus infection
and illness may lead to the development of drugs to combat the disease.
One example of this is from Dr. Ove Lundgren, of Goteborg University
in Sweden. His study gave drugs to mice that inhibited the nervous
system of the gut, finding that within two days of being infected
with rotavirus, only six out of 14 mice receiving treatment developed
diarrhea, compared to 14 out of 15 mice that were infected but didn't
receive the medicine.
On August 1998, a
vaccine known as Rotashieldâ was developed and released for
the prevention of rotavirus infections. Proven to decrease the morbidity
and mortality of rotavirus infections, the new vaccine was touted
as a miracle shot that may save the lives of thousands of children.
Unfortunately, in July 1999, the CDC recommended use of the vaccine
be halted due to the potential link with intussusception, a type
of bowel obstruction that occurs when the bowel folds in on itself,
possibly requiring surgery to repair.
Although this link
has not yet been proven, Wyeth Laboratories Inc. of Marietta, Pa.,
voluntarily ceased further distribution of the vaccine, in consultation
with the U.S. Food and Drug Administration. Scientists at Children's
Hospital Medical Center in Cincinnati have developed a new rotavirus
vaccine that appears to be up to 89 percent effective at preventing
the disease, but is still being tested.
working on the development of a reliable and consistent method for
the detection of rotavirus in water that will also provide a practical
means of routine monitoring. The use of molecular-based methods
that target viral genomes appears to be the most likely means of
virus detection in water in the future. Other methods being investigated
include: combined use of cell culture and the molecular polymerase
chain reaction (PCR) approach, microscopic methods and flow cytometry.
Risk assessment modeling, a mathematical approach to predicting
the risks of infection from waterborne pathogens, is also being
streamlined for rotavirus.
As always, it's best to avoid infection with viral pathogens in
the first place rather than rely on post-infection treatments. Prevention
includes the improvement of sanitary conditions, health education
and better nutrition. Good hygiene, including frequent handwashing,
is a necessary step for infection control of rotavirus and a variety
of other human pathogens. Finally, chemical disinfection and water
purification methods effective against viruses are necessary to
prevent virus transmission from contaminated waterborne routes.
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of infectious rotaviruses in environmental and clinical samples,"
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2. Gale, P., "Developments in microbiological risk assessment
models for drinking water-a short review," Journal of Applied
Bacteriology, 81: 403-410, 1996.
3. LeGuyader, F., E. Dubois, D. Menard, and M. Pommepuy, "Detection
of hepatitis A virus rotavirus and enterovirus in naturally contaminated
shellfish and sediment by RT-seminested PCR," Applied Environmental
Microbiology, 60: 3665-3671, 1994.
4. Lundgren O., A.T. Peregrin, K. Persson, S. Kordasti, I. Uhnoo
and L. Svensson, "Role of the Enteric Nervous System in the
Fluid and Electrolyte Secretion of Rotavirus Diarrhea," Science,
Jan. 21; 287: 491-495, 2000.
5. U.S. Centers for Disease Control & Prevention (CDC), "Withdrawal
of rotavirus vacine recommendation," Morbidity and Mortality
Weekly Report (MMWR), 48:1007, 1999.
6. CDC, "Rotavirus surveillance-United States, 1989-1990,"
MMWR, 40: 1991.
7. CDC, "Rotavirus surveillance-United States, 1997-1998,"
MMWR, 47:978-980, 1999.
Images in this article can be found on the website: www.rotavirus.com