[Seasonality of dengue reporting in state capitals in the Brazilian Amazon and impacts of El Niño/La Niña].

The dynamics of dengue transmission are multifactorial and involve socioeconomic, ecological, and environmental aspects, the latter being closely related to local climatic conditions that affect the vector's reproductive cycle. Climate depends in turn on tropical oceanic mechanisms such as phases of El Niño/La Niña over the Pacific. The study contributes to this discussion and reports on the correlations between the Multivariate ENSO Index (MEI) in the Pacific and the number of reported dengue cases in seven state capitals in the Brazilian Amazon from 2001 to 2012. The study also analyzes the seasonality pattern (quarterly mean values) in dengue cases throughout the region. Evidence that El Niño/La Niña causes a decrease versus increase in the local rainfall pattern is consistent with the lower versus higher number of reported dengue cases in most of the state capitals in the Amazon, a result proven by the statistically significant negative correlations seen in Manaus (Amazonas), São Luís (Maranhão), Belém (Pará) and Palmas (Tocantins). The 12-years means (2001-2012) revealed the presence of pronounced seasonality in dengue incidence in the majority of the state capitals, with sharp peaks from January to March [Rio Branco (Acre), Manaus, Belém and Palmas] and from April to June (São Luís), corresponding to 50-70% of the annual total. State capitals farther north [Boa Vista (Roraima) and Macapá (Amapá)] showed dengue reporting in all quarters of the year, with no pronounced seasonality.