The Effects of Weather and Climate on the Seasonality of Influenza: What We Know and What We Need to Know

Influenza is one of the most deadly of all airborne and upper-respiratory infections. On average, 22,000 deaths and over 3 million hospitalizations in USA are attributed to influenza each year. The distinct seasonality of influenza suggests a climate connection, but the wide range of methodologies used to explore this connection makes it difficult to elucidate a definitive relationship. Much of what is known about the effects of weather and climate on the seasonality of influenza stems from research conducted by members of the public health and medical communities, with few contributions from other physical and social science fields. Most of these studies are either based on experiments conducted under controlled laboratory conditions or on the broad-scale patterns of morbidity and mortality and their relationship to large-scale climate signals. What remains largely unknown is the suitability of these results for the development of early warning systems and for determining the dynamics of viral transmission on multiple space and time scales.