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Author: Colas de la Noue A et al. (2014) Source: Appl. Environ. Microbiol. doi:10.1128/AEM.01871-14. AEM Accepts, published online ahead of print on 12 September 2014.

STUDY

Colas de la Noue A et al. (2014)

Absolute humidity influences the seasonal persistence and infectivity of human norovirus.

Background: Around the globe, norovirus ranks among the major pathogens of acute gastroenteritis. In temperate climate zones, outbreaks reach their seasonal peak during the cold months. Up to now, it has been unknown how climatic factors influence norovirus outbreaks. Hence, the authors investigated the influence of humidity on the infectivity of norovirus.


Methods: The laboratory study used murine norovirus (MNV) as surrogate for human norovirus. The researchers analysed the persistence of MNV when exposed to different levels of relative humidity (RH), ranging from 10 % (low humidity) to 100 % (completely saturated air), at 9 °C and 25 °C. Afterwards, they determined the infectivity by titration in cell culture. Similar experiments were carried out with virus-like particles (VLP) of human norovirus to investigate changes in binding patterns to carbohydrates (A, B, O) that might reflect capsid alterations.


Results: Reactions of MNV and VLP to humidity were similar. 10 % and 100 % RH had a strong conserving effect on MNV and VLP; 50 % RH reduced both MNV infectivity and VLP binding capacity. Additional data analyses indicate that it is rather the absolute humidity (AH) than RH that decisively influences the infectivity of norovirus, with a low AH (<0.007 kg water/kg air) being ideal for keeping norovirus infectious. Analysis of meteorological data in Paris (daily records of AH and temperature from 2000-2013) showed that during winter in 96.3 % of cases the AH had been below 0.007 kg water/kg air, in summer, however, only in 20.3 % of cases.


Conclusions: The results suggest that the low AH values during the winter season provide ideal conditions for the persistence and thus the transmission of norovirus. Exact measurement of environmental parameters such as AH can contribute to gaining further insights in the epidemiology and transmission of norovirus.


Source:
Appl. Environ. Microbiol. doi:10.1128/AEM.01871-14. AEM Accepts, published online ahead of print on 12 September 2014.


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Practical tip: Hygiene management in case of noroviruses.