Outbreaks of tularemia in a boreal forest region depends on mosquito prevalence.

Authors:
Address: Department of Mathematics and Mathematical Statistics, Computational Life Science Cluster, Umeå University, Sweden.
Journal:

Publication:
Free Text: Outbreaks of tularemia in a boreal forest region depends on mosquito prevalence.

abstract

BACKGROUND:

We aimed to evaluate the potential association of mosquito prevalence in a boreal forest area with transmission of the bacterial disease tularemia to humans, and model the annual variation of disease using local weather data.

METHODS:

A prediction model for mosquito abundance was built using weather and mosquito catch data. Then a negative binomial regression model based on the predicted mosquito abundance and local weather data was built to predict annual numbers of humans contracting tularemia in Dalarna County, Sweden.

RESULTS:

Three hundred seventy humans were diagnosed with tularemia between 1981 and 2007, 94% of them during 7 summer Outbreaks. Disease transmission was concentrated along rivers in the area. The predicted mosquito abundance was correlated (0.41, P < .05) with the annual number of human cases. The predicted mosquito peaks consistently preceded the median onset time of human tularemia (temporal correlation, 0.76; P < .05). Our final predictive model included 5 environmental variables and identified 6 of the 7 outbreaks.

CONCLUSIONS:

This work suggests that a high prevalence of mosquitoes in late summer is a prerequisite for outbreaks of tularemia in a tularemia-endemic boreal forest area of Sweden and that environmental variables can be used as risk indicators.

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