Long-Term and Seasonal Dynamics of Dengue in Iquitos, Peru

Abstract

IntroductionLong-term disease surveillance data provide a basis for studying drivers of pathogen transmission dynamics. Dengue is a mosquito-borne disease caused by four distinct, but related, viruses (DENV-1-4) that potentially affect over half the world's population. Dengue incidence varies seasonally and on longer time scales, presumably driven by the interaction of climate and host susceptibility. Precise understanding of dengue dynamics is constrained, however, by the relative paucity of laboratory-confirmed longitudinal data.MethodsWe studied 10 years (2000–2010) of laboratory-confirmed, clinic-based surveillance data collected in Iquitos, Peru. We characterized inter and intra-annual patterns of dengue dynamics on a weekly time scale using wavelet analysis. We explored the relationships of case counts to climatic variables with cross-correlation maps on annual and trimester bases.FindingsTransmission was dominated by single serotypes, first DENV-3 (2001–2007) then DENV-4 (2008–2010). After 2003, incidence fluctuated inter-annually with outbreaks usually occurring between October and April. We detected a strong positive autocorrelation in case counts at a lag of ∼70 weeks, indicating a shift in the timing of peak incidence year-to-year. All climatic variables showed modest seasonality and correlated weakly with the number of reported dengue cases across a range of time lags. Cases were reduced after citywide insecticide fumigation if conducted early in the transmission season.ConclusionsDengue case counts peaked seasonally despite limited intra-annual variation in climate conditions. Contrary to expectations for this mosquito-borne disease, no climatic variable considered exhibited a strong relationship with transmission. Vector control operations did, however, appear to have a significant impact on transmission some years. Our results indicate that a complicated interplay of factors underlie DENV transmission in contexts such as Iquitos.

The relationship between entomological indicators of Aedes aegypti abundance and dengue virus infection

“…aegypti density and DENV risk. Over the period included in this analysis, there were large scale vector control interventions from October 2002-Jan 2003 and others in late 2003 [42]. Nevertheless, the majority of our data included periods where there was not extensive vector control.…”

Análisis exploratorio de ondículas de los patrones de estacionalidad del dengue en Colombia

“…Esta técnica ya había sido utilizada previamente en diversos contextos epidemiológicos, incluidos algunos relativamente similares al colombiano, para determinar diferencias en los patrones estacionarios de la enfermedad (10,13,20,22). En Perú, por ejemplo, el análisis de ondículas permitió recientemente encontrar diferencias en los ciclos de transmisión en las tres grandes regiones de ese país: costa, sierra y selva (20).…”

“…En Perú, por ejemplo, el análisis de ondículas permitió recientemente encontrar diferencias en los ciclos de transmisión en las tres grandes regiones de ese país: costa, sierra y selva (20). En estudios similares realizados en otros países, esta técnica (18,(21)(22)(23)(24)(25) se ha empleado no solo para el estudio de la estacionalidad del dengue, sino también, para el del comportamiento histórico de otras enfermedades infecciosas como el cólera (12), el sarampión (12,17) y la influenza (21).…”

“…Desde el punto de vista epidemiológico, esto sucede cuando se dan cambios en la estacionalidad de un fenómeno o este tiene patrones complejos y ruidosos, como puede pasar con series de tiempo muy largas, o en el caso de las enfermedades infecciosas cuando cambian los patrones de transmisión debido a los cambios en el tiempo de los factores determinantes de su aparición (16). Esta técnica se ha utilizado ampliamente en epidemiología para el análisis del comportamiento de las enfermedades infecciosas, especialmente para analizar su relación con las variables climáticas (12,(17)(18)(19)(20)(21)(22)(23)(24)(25).…”

Impacts of Dengue Epidemics on Household Labor Market Outcomes

“…Although temperatures likely play a role in dengue transmission, Stoddard et al (2014) find that dengue incidence varies both seasonally and across years for a variety of complex reasons. A likely cause of dengue epidemics is the introduction of a new serotype of the virus into the affected population.…”