Estimated effect of climatic variables on the transmission of Plasmodium vivax malaria in the Republic of Korea.
BACKGROUND
Climate change may affect Plasmodium vivax malaria transmission in a wide region including both subtropical and temperate areas.


OBJECTIVE
We aimed to estimate the effects of climatic variables on the transmission of P. vivax in temperate regions.


METHODS
We estimated the effects of climatic factors on P. vivax malaria transmission using data on weekly numbers of malaria cases for the years 2001-2009 in the Republic of Korea. Generalized linear Poisson models and distributed lag nonlinear models (DLNM) were adopted to estimate the effects of temperature, relative humidity, temperature fluctuation, duration of sunshine, and rainfall on malaria transmission while adjusting for seasonal variation, between-year variation, and other climatic factors.


RESULTS
A 1°C increase in temperature was associated with a 17.7% [95% confidence interval (CI): 16.9, 18.6%] increase in malaria incidence after a 3-week lag, a 10% rise in relative humidity was associated with 40.7% (95% CI: -44.3, -36.9%) decrease in malaria after a 7-week lag, a 1°C increase in the diurnal temperature range was associated with a 24.1% (95% CI: -26.7, -21.4%) decrease in malaria after a 7-week lag, and a 10-hr increase in sunshine per week was associated with a 5.1% (95% CI: -8.4, -1.7%) decrease in malaria after a 2-week lag. The cumulative relative risk for a 10-mm increase in rainfall (≤ 350 mm) on P. vivax malaria was 3.61 (95% CI: 1.69, 7.72) based on a DLNM with a 10-week maximum lag.


CONCLUSIONS
Our findings suggest that malaria transmission in temperate areas is highly dependent on climate factors. In addition, lagged estimates of the effect of rainfall on malaria are consistent with the time necessary for mosquito development and P. vivax incubation.
Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, Jangan-gu, Suwon, Republic of Korea.
Young-Min
YM
Kim
Jae-Won
JW
Park
Hae-Kwan
HK
Cheong
D000818:Animals; D002980:Climate; D057231:Climate Change; D009033:Culicidae / Q000502:physiology*; D006801:Humans; D015994:Incidence; D016014:Linear Models; D016780:Malaria, Vivax / Q000453:epidemiology* / Q000635:transmission*; D008954:Models, Biological; D010966:Plasmodium vivax / Q000502:physiology; D016012:Poisson Distribution; D056910:Republic of Korea / Q000453:epidemiology; D012621:Seasons; D013997:Time Factors