Host, weather and virological factors drive norovirus epidemiology: time-series analysis of laboratory surveillance data in England and Wales

Norovirus, the most commonly identified cause of both sporadic cases and outbreaks of infectious diarrhoea in developed countries, exhibits a complex epidemiology and has a strong wintertime seasonality. Viral populations are dynamic and evolve under positive selection pressure. Time series-adapted...

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Bibliographic Details
Published in:	PloS one 2009-08, Vol.4 (8), p.e6671-e6671
Main Authors:	Lopman, Ben, Armstrong, Ben, Atchison, Christina, Gray, Jim J
Format:	Article
Language:	eng
Subjects:	Analysis Antigenic variants Antigens Caliciviridae Infections - epidemiology Caliciviridae Infections - virology Campylobacter Cholera Confounding Factors (Epidemiology) Daily temperatures Developed countries Diarrhea Disease control E coli Emergence England - epidemiology Epidemics Epidemiology Escherichia coli Food contamination & poisoning Gastroenteritis - epidemiology Gastroenteritis - virology Genetic diversity Genotype & phenotype Health surveillance Herd immunity Host-Pathogen Interactions Humans Humidity Hygiene Immunity Infections Infectious Diseases/Gastrointestinal Infections Infectious Diseases/Nosocomial and Healthcare-Associated Infections Influenza Laboratories Norovirus - pathogenicity Outbreaks Poisson density functions Poisson Distribution Population Population Surveillance Positive selection Precipitation Public health Public Health and Epidemiology/Infectious Diseases Rain Regression analysis Regression models Relative humidity Seasonal variations Statistical analysis Surveillance Temperature effects Time series Virology Virology/Virus Evolution and Symbiosis Viruses Wales - epidemiology Weather
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Summary:	Norovirus, the most commonly identified cause of both sporadic cases and outbreaks of infectious diarrhoea in developed countries, exhibits a complex epidemiology and has a strong wintertime seasonality. Viral populations are dynamic and evolve under positive selection pressure. Time series-adapted Poisson regression models were fitted to daily counts of laboratory reports of norovirus in England and Wales from 1993 to 2006. Inverse linear associations with daily temperature over the previous seven weeks (rate ratio (RR) = 0.85; 95% CI: 0.83 to 0.86 for every 1 degrees C increase) and relative humidity over the previous five weeks (RR = 0.980; 95% CI: 0.973 to 0.987 for every 1% increase) were found, with temperature having a greater overall effect. The emergence of new norovirus variants (RR = 1.16; 95% CI: 1.10 to 1.22) and low population immunity were also associated with heightened norovirus activity. Temperature and humidity, which may be localised, had highly consistent effects in each region of England and Wales. These results point to a complex interplay between host, viral and climatic factors driving norovirus epidemic patterns. Increases in norovirus are associated with cold, dry temperature, low population immunity and the emergence of novel genogroup 2 type 4 antigenic variants.
ISSN:	1932-6203 1932-6203