Abstract
Hand, foot, and mouth disease (HFMD) causes characteristic blisters and sores mainly in infants and children, and has been monitored in South Korea through sentinel surveillance since 2009. We described the patterns of HFMD occurrence and analyzed the effect of climatic factors on national HFMD incidence. Weekly clinically diagnosed HFMD case rates (per 1,000 outpatients) in sentinel sites and weekly climatic factors, such as average temperature, relative humidity, duration of sunshine, precipitation, and wind speed from 2010 to 2013, were used in this study. A generalized additive model with smoothing splines and climatic variables with time lags of up to 2 weeks were considered in the modeling process. To account for long-term trends and seasonality, we controlled for each year and their corresponding weeks. The autocorrelation issue was also adjusted by using autocorrelation variables. At an average temperature below 18°C, the HFMD rate increased by 10.3% for every 1°C rise in average temperature (95% confidence interval (CI): 8.4, 12.3%). We also saw a 6.6% increase in HFMD rate (95% CI: 3.6, 9.7%) with every 1% increase in relative humidity under 65%, with a 1.5% decrease in HFMD rate observed (95% CI: 0.4, 2.7%) with each 1% humidity increase above 65%. Modeling results have shown that average temperature and relative humidity are related to HFMD rate. Additional research on the environmental risk factors of HFMD transmission is required to understand the underlying mechanism between climatic factors and HFMD incidence.
Highlights
Hand, foot, and mouth disease (HFMD) is caused by members of the genus Enterovirus, mainly by enterovirus 71 (EV 71) and different subtypes of Coxsackie virus, including CA16 [1]
Simple correlation analysis revealed that the HFMD rate was positively correlated with average temperature, relative humidity, and precipitation, and negatively correlated with sunshine (Table 2)
Relative humidity was highly correlated with other climatic variables, and it was not included in the same model with other factors, with the exception of wind speed, to avoid potential collinearity
Summary
Foot, and mouth disease (HFMD) is caused by members of the genus Enterovirus, mainly by enterovirus 71 (EV 71) and different subtypes of Coxsackie virus, including CA16 [1]. HFMD is usually transmitted through direct contact with infected individuals and environmental factors [2]. The symptoms of this viral disease include blisters and sores in the mouth, on the palms of the hands, and on the soles of the feet, with a 3–7 day incubation period [3]. It is known to be a self-limiting condition from which a person can recover naturally, rarely, patients demonstrate severe complications, such as encephalitis, meningitis, and flaccid paralysis, which can lead to death, in infants infected with EV 71 [4]. An PLOS ONE | DOI:10.1371/journal.pone.0157500 June 10, 2016
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