Impact of temperature on hand, foot and mouth disease and its attributable risk in Guangdong province

  Objective  To study the impact of ambient temperature on hand, foot and mouth disease (HFMD) and to explore the source of heterogeneity in the impact and the HFMD burden attributable to ambient temperature in Guangdong province.

  Methods  The data on daily reported HFMD cases and meteorological condition from 2009 through 2016 in Guangdong province were collected. The distributed lag nonlinear model (DLNM) was adopted to assess the effect of average daily ambient temperature on HFMD incidence at city level with the pooled effect estimates from multivariate meta-regression model analysis. Fraction and number of HFMD incidents attributable to variation in ambient temperature were estimated according to the results of DLNM analysis.

  Results   Totally 2 279 647 HFMD cases were reported during the period. The risk of HFMD incidence increased with the increment of average daily ambient temperature. The cumulative relative risk (RR) of HFMD incidence reached the highest for the average daily ambient temperature of 30.5 ℃ versus that of 24 ℃ (RR = 1.24, 95% confidence interval 95% CI: 1.12 – 1.37). The most obvious effect of low average daily ambient temperature on HFMD incidence was on the lag day 8 but that of high temperature was on the lag day zero. The disparity in the effect of average daily ambient temperature on HFMD incidence among various cities was derived from population density, growth rate of gross domestic production, location longitude, and average annual temperature/humidity/hours of sunshine. The estimated total number of HFMD incidents attributed to the exposure to high average daily temperature was 241 918, accounting for 10.61% (95% CI: 9.67% – 11.53%) of all the cases during the period. When exposed to high average daily ambient temperature, the elderly and the children less than 5 years old were at a higher risk of HFMD incidence than other populations.

  Conclusion  High average daily ambient temperature could increase the risk of HFMD incidence and the impact of the high temperature may appear immediately or at lag days. The results suggest that specific measures should be taken in vulnerable populations during seasons with high temperature for the prevention of HFMD incidents.