Seasonality and H1N1

The paper “Estimated epidemiologic parameters and morbidity associated with pandemic (H1N1) influenza” 1 fails to consider the impact of environment — the third apex of the epidemiological triangle — on the reproductive number of H1N1. Influenza is well-known to be a seasonal disease. The period studied by this paper fell mostly outside of what is usually considered to be “flu season.” This observation calls into question the authors’ core conclusion about the potential effectiveness of non-medical mitigation strategies on an in-season outbreak.