Norovirus: Up to 800 Deaths Annually Incidence in US

Larry Hand

July 10, 2013

For a vaccine to have the maximum effect against norovirus, it would have to be safe and effective in young children and the elderly, as well as healthcare workers, travelers, and military personnel, according to an article published online July 10 in Emerging Infectious Diseases.

Aron J. Hall, DVM, MSPH, an epidemiologist with the Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, and colleagues analyzed 7 previously published studies of US disease incidence published during the last 5 years. The studies used various methods, including attributable proportion extrapolation, population-based surveillance, and indirect modeling.

Building on those studies, Dr. Hall and colleagues developed estimates of the overall US norovirus disease burden, including estimates for specific age groups and disease outcomes. The authors note that although disease outbreaks have been widely studied, obtaining overall prevalence estimates has been difficult until now.

Norovirsu is the leading cause of acute gastroenteritis across all age groups. "Norovirus causes an average of 570–800 deaths, 56,000–71,000 hospitalizations, 400,000 emergency department visits, 1.7–1.9 million outpatient visits, and 19–21 million total illnesses per year," the researchers write.

However, persons aged 65 years or older are at greatest risk for norovirus-associated death, and children younger than 5 years present with the most cases of norovirus-associated healthcare visits.

"On the basis of these rates of disease and a life expectancy of 79 years, a US resident would experience 5 episodes of norovirus gastroenteritis in his or her lifetime and an average lifetime risk for norovirus-associated outpatient visit, ED visit, hospitalization, and death of 1 in 2, 1 in 9, 1 in 50–70, and 1 in 5,000–7,000, respectively," the researchers write.

The prevalence data are particularly timely because a candidate norovirus vaccine is near phase 3 study and could possibly be licensed within 5 to 7 years, the researchers note. Further research should concentrate on age-specific rates of norovirus disease, as well as the causal role of norovirus and common concurrent conditions, they conclude.

In an accompanying article, Dr. Hall and colleagues describe the ongoing efforts of the National Outbreak Reporting System (NORS), which launched in 2009 as an expansion and enhancement of the Foodborne Disease Outbreaks Surveillance System and the Waterborne Disease and Outbreak Surveillance System.

Of 4455 outbreaks reported through NORS in 2009 to 2010, 4376 (98%) were acute gastroenteritis outbreaks reported by the District of Columbia, Puerto Rico, and all states except Delaware. The outbreaks were associated with 122,488 illnesses, 2952 hospitalizations, and 168 deaths. Norovirus was responsible for 1908 (68%) outbreaks, which were associated with 69,145 illnesses, 1093 (46%) hospitalizations, and 125 (86%) deaths.

Emerg Infect Dis. Published online July 10, 2013. Full text

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