Norovirus – Credit HPA
# 7020
Prior to the introduction of a pair of live, attenuated Rotavirus vaccines in the middle of the last decade (RotaTeq and Rotarix), nearly all children in the United States were infected by one of the Rotaviruses before their 5th birthday (cite).
The CDC estimated the pre-vaccine disease burden in the United States each year as:
• more than 400,000 doctor visits,
• more than 200,000 emergency room visits,
• 55,000 to 70,000 hospitalizations, and
• 20-60 deaths
With the introduction of the Rotavirus vaccine in 2006, the number youngsters needing emergency department care or hospitalization due to the Rotavirus had dropped by about 85% by 2010 (cite).
As the number of Rotavirus cases begins to go down, it is not terribly surprising to find a new king of the stomach virus hill among children.
From a study just published in the New England Journal of Medicine, we learn that Norovirus has now taken the lead as the number one cause of gastroenteritis in children in the United States.
Special Article
Norovirus and Medically Attended Gastroenteritis in U.S. Children
Daniel C. Payne, Ph.D., M.S.P.H., Jan Vinjé, Ph.D., Peter G. Szilagyi, M.D., M.P.H., Kathryn M. Edwards, M.D., Mary Allen Staat, M.D., M.P.H., Geoffrey A. Weinberg, M.D., Caroline B. Hall, M.D., James Chappell, M.D., Ph.D., David I. Bernstein, M.D., Aaron T. Curns, M.P.H., Mary Wikswo, M.P.H., S. Hannah Shirley, B.S. , Aron J. Hall, D.V.M., M.S.P.H., Benjamin Lopman, Ph.D., M.P.H., and Umesh D. Parashar, M.B., B.S., M.P.H.
N Engl J Med 2013; 368:1121-1130
March 21, 2013 DOI: 10.1056/NEJMsa1206589
<SNIP>
Conclusions
Since the introduction of rotavirus vaccines, norovirus has become the leading cause of medically attended acute gastroenteritis in U.S. children and is associated with nearly 1 million health care visits annually. (Funded by the Centers for Disease Control and Prevention.)
For some more background on this CDC-funded study, we go to the CDC Newsroom.
Norovirus is now the leading cause of severe gastroenteritis in US children
Norovirus is now the leading cause of acute gastroenteritis among children less than 5 years of age who seek medical care, according to a new study published in the New England Journal of Medicine. Norovirus was responsible for nearly 1 million pediatric medical care visits for 2009 and 2010 in the United States, amounting to hundreds of millions of dollars in treatment costs each year.
“Infants and young children are very susceptible to norovirus infections, which often result in a high risk of getting dehydrated from the sudden onset of intense vomiting and severe diarrhea,” said Dr. Daniel Payne, an epidemiologist in the Division of Viral Diseases at the Centers for Disease Control and Prevention. “Our study estimates that 1 in 278 U.S. children will be hospitalized for norovirus illness by the time they turn 5 years of age. It is also estimated that about 1 in 14 children will visit an emergency room and 1 in 6 will receive outpatient care for norovirus infections.”
<SNIP>
“Our study confirmed that medical visits for rotavirus illness have decreased,” said Dr. Payne. “Also, our study reinforces the success of the U.S. rotavirus vaccination program and also emphasize the value of specific interventions to protect against norovirus illness.” Norovirus vaccines are currently being developed, which may be especially important for young children and elderly people who are high risk.
Noroviruses, which are often mistakenly called `stomach flu’, are single-stranded RNA viruses that are able to evolve rapidly, so we typically see a new dominant norovirus strain emerge every two or three years.
After exposure and a short incubation period (12-24 hours), the victim usually experiences nausea, frequent vomiting & diarrhea, and stomach pain – and may also experience headache, fever, and body aches.
The illness generally runs its course in 1 to 3 (very long) days, and most people recover. But among those who are aged or infirmed, the virus can take a heavy toll. According to the CDC, each year the norovirus:
- causes about 21 million cases of acute gastroenteritis (inflammation of the stomach or intestines or both)
- contributes to about 70,000 hospitalizations and 800 deaths, mostly among young children and the elderly
There are five genogroups (GI, GII, GIII, GIV, and GV) of noroviruses that can infect a variety of species, but most human infections stem from genogroups GI and GII. GII noroviruses have at least 19 subtypes.
The most common cause of human illness is from Genogroup II, genotype 4 (abbreviated as GII.4).
In 2009, we saw the emergence of the New Orleans strain of GII.4, which had been the dominant strain for the past three years.
That is, until a new strain discovered a year ago by Professor Peter White and his team in the School of Biotechnology and Biomolecular Sciences in Australia (see UNSW: Sydney 2012 Norovirus Rising) - began to spread globally last fall.
In short order it was being reported in Japan, Taiwan, Europe, the UK, and North America (see Eurosurveillance: Emergence & Spread Of GII.4 Variant Norovirus).
According to a recent MMWR Report On New Norovirus GII.4 Sydney Strain, by December of 2012, the new Sydney strain was the cause of 58% of the norovirus outbreaks across the United States.
While reportedly `no worse’ than previous strains (which admittedly isn’t much comfort for those afflicted), levels of immunity to this emerging strain are exceedingly low, and it spreads like wildfire (see Vomiting Larry And His Aerosolized Norovirus).
Without a vaccine (yet) against Norovirus, prevention is key.
One of the best preventatives is good hand hygiene, unfortunately, unlike with many other bacteria and viruses, alcohol gel doesn’t do a particularly good job of killing the virus (see CMAJ: Hand Sanitizers May Be `Suboptimal’ For Preventing Norovirus).
The CDC offers this advice to help prevent the spread of this virus.
