Potential impact of influenza A/H1N1 pandemic and hand-gels on acute diarrhea epidemic in France.

Background: The 2009 A/H1N1 influenza pandemic has received a great deal of attention from public health authorities. Our study examines whether this pandemic and the resulting public health measures could have impacted acute diarrhea, a prevalent, highly transmissible and historically monitored disease.
Methods: Using augmentation procedures of national data for the previous five years (2004-2009), we estimated the expected timing and incidence of acute diarrhea in France in 2009-2010 and evaluated differences with the observed. We also reviewed national hand gels for the same period.
Findings: Number of episodes of acute diarrhea in France in 2009-2010 was significantly lower than expected until the third week of December (-24%, 95% CI [-36%; -9%]), then significantly higher (+40%, 95% CI [22%; 62%]), leading to a surplus of 574,440 episodes. The epidemic was delayed by 5 weeks with a peak 1.3 times higher than expected. Hand-gels sales inversely correlated with incidence of both influenza-like illness and acute diarrheal disease. Among individuals >65 yo, no excess cases of influenza and no excess rebound in acute diarrhea were observed, despite similar delay in the onset of the seasonal diarrheal epidemic.
Interpretation: Our results suggest that at least one endemic disease had an unexpected behavior in 2009-2010. Acute diarrhea seems to have been controlled during the beginning of the pandemic in all age groups, but later peaked higher than expected in the younger population. The all-age delay in seasonal onset seems partly attributable to hand-gels use, while the differential magnitude of the seasonal epidemic between young and old, concurrent for both influenza and acute diarrhea, is compatible with disease interaction.