A new study showed that the incidence of acute gastroenteritis (AG) reported by general practitioners (GPs) and emergency departments was lower following the emergence of norovirus GII.4 2012.

Acute gastroenteritis (AG) is commonly defined as diarrhoea (three or more loose stools) or vomiting in the past 24 hours [1]. AG can be caused by different viruses, bacteria, and parasites, as well as chemicals and other non-infectious agents.

In France, it has been estimated that more than 21 million AG cases occur each year, leading to between 1.5 and 4 million general practitioners (GP) visits by adults during the winter period.

AG occurs related to an increase in AG of viral origin, mainly norovirus and rotavirus. AG incidence is higher in children and rotavirus is the most common cause of severe AG in young children.

In the present study, the researchers analysed 25 years of general practitioner (GP) visits for acute gastroenteritis (AG) surveillance in France, by the GP Sentinelles network. The team searched for time trends of acute gastroenteritis incidence during winter periods.

Data from emergency departments and drug reimbursement were additional data sources. A time-series analysis was performed using a generalised additive model for all data sources for the winter period.

Virological data were incorporated and compared with the three data sources. The cumulative incidence of GP visits for winter AG exhibited an increasing trend from 1991 until 2008, when it reached 6,466 per 100,000 inhabitants.

The incidence decreased thereafter to 3,918 per 100,000 inhabitants in 2015. The decreasing trend was observed for all age groups and confirmed by the generalised additive model. For emergency department visits a decreasing trend was observed from 2004.

Drug reimbursement data analyses demonstrated a decreasing trend from when data began in 2009. The AG incidence reported by GPs and emergency departments was lower following the emergence of norovirus GII.4 2012 (p < 0.0001).

Analyses performed on three independent datasets showed a similar decreasing trend for AG activity, suggesting that thE trend is not an artefact. However, there is no clear explanation for the decreasing trend and the researchers will discuss the different hypothesis that could explain the phenomena.

Winter AG incidences seem to follow long-term rising and decreasing trends that are important to monitor through continuous surveillance to evaluate the impact of prevention strategies, such as future immunisation against acute viral gastroenteritis, the researchers said.