Date Published: November 17, 2009
Publisher: Public Library of Science
Author(s): Pejman Rohani
Abstract: Pejman Rohani discusses a new study that examined the dynamic relationship between climate variables and dengue incidence in Thailand, Mexico, and Puerto Rico.
Partial Text: The current H1N1 influenza pandemic has highlighted the practical usefulness of knowing ahead of time about an impending large outbreak. Specifically, as the flu season in the northern hemisphere gets into full swing, public health decision makers have been using information gleaned from epidemics in Mexico and the US earlier this spring to prepare proactive mitigation and control strategies.
In a new study by Johansson and colleagues published in this issue of PLoS Medicine, the authors carry out statistical time-series analyses to examine the dynamic relationship between climate variables and the incidence of dengue in Thailand, Mexico, and Puerto Rico. They find no systematic association between multi-annual dengue outbreaks and El Niño Southern Oscillation.
The absence of a predictable consequence of ENSO for dengue transmission is an important piece of information for the development of early warning systems. However, the authors are very careful in interpreting their findings and suggest that given the known mechanistic environmental drivers of vector biology, it remains formally possible that ENSO might play a role in dengue transmission. In this light, their findings may be explained along two distinct lines. They may reflect inadequacies in the time-series data (ideally, they would span a longer period and contain higher spatial resolution), or that intrinsic processes such as human birth rates or serotype interactions via immunological mechanisms simply swamp any signatures of the impact of ENSO. For these reasons, this careful work by Johansson et al. is both scientifically interesting and very timely.