Community Incidence of Norovirus-associated Infectious Intestinal Disease in England: Improved Estimates Using Viral Load for Norovirus Diagnosis

Existing estimates of the incidence of infectious intestinal disease (IID) caused by norovirus are based on
electron microscopy or reverse transcription-polymerase chain reaction (RT-PCR). Neither method accurately
represents norovirus disease burden: Electron microscopy has poor diagnostic sensitivity, and RT-PCR has poor
diagnostic specificity. In this study, viral load measurements were used to identify cases of norovirus-associated
IID and to produce new incidence estimates for England. IID cases were ascertained in the Study of Infectious
Intestinal Disease in England (1993–1996), and stool specimens were tested by semiquantitative real-time RTPCR
for norovirus. The age-adjusted community incidence of norovirus-associated IID was 4.5/100 person-years
(95% credibility interval: 3.8, 5.2), equating to 2 million episodes/year. Among children aged less than 5 years, the
community incidence was 21.4/100 person-years (95% credibility interval: 15.9, 27.7), and the incidence of consultations
to general practitioners for norovirus-associated IID was 3.2/100 person-years (95% credibility interval:
2.6, 3.8), with 100,000 children visiting their general practitioner for norovirus-associated IID each year. Norovirus
is the most common cause of IID in the community in England and is responsible for a similar number of pediatric
primary care consultations as rotavirus.

Citation:
Phillips, G., Tam, C.C., Conti, S., Rodrigues, L.C., Brown, D., Iturriza-Gomara, M., Gray, J. and Lopman, B. (2010), 'Community Incidence of Norovirus-associated Infectious Intestinal Disease in England: Improved Estimates Using Viral Load for Norovirus Diagnosis', American Journal of Epidemiology,171(9), pp.1014-1022, DOI: 10.1093/aje/kwq021.