Objective To assess the influence of meteorological factors on the incidence of mumps.
Methods The daily data of reported mumps cases and meteorological variables in Lanzhou from 2008 to 2016 were obtained from the National Infections Disease Report Information Management System and the Gansu Meteordogical Bureau. With the annual mean temperature (11.11℃) of Lanzhou as reference, the RR of daily mean temperature above this value to the onset of mumps was calculated, and the P75 and P95 of daily mean temperature were used to describe high temperature effect; the RR of daily mean temperature below this value to the onset of mumps was calculated, and the P5 and P25 of the daily mean temperature were used to describe low temperature effect. The relationships of temperature and relative humidity with the incidence of mumps were examined by distributed lag non-linear model (DLNM), adjusted for long-time trend, monthly variation, day-of-the-week effect, and holiday effect.
Results A total of 11 762 cases were reported from 2008 to 2016, the ratio of male to female was 1.52:1, and the children aged 6-14 years accounted for 49.67%. There was a non-linear relationship between temperature and mumps, and were acute and shortterm lag effects at both high temperature and low temperature. The RR (95%CI) was highest at 26℃ on lag 1d for high temperature days>12.7℃ (P50), which was 1.32(1.05-1.65), and at -2℃ on lag 0d for low temperature days (< 12.7℃), which was 1.26(1.05-1.51). At 20.1℃ (P75) and 25.4℃ (P95), the cumulative effect on the onset of mumps was significant from lag 0-3 d to lag 0-7 d, with the highest RR of 1.43 (1.12-1.81) and 1.83 (1.34-2.50) on lag 0-3 d, respectively. At -5.2℃ (P5) and 1.7℃ (P25), the cumulative effect of the onset of mumps showed statistical significance from lag 0-3d to lag 0-14d, with the highest RR of 1.95(1.41-2.70) and 1.62(1.25-2.09) on lag 0-7 d, respectively. The children aged 6-14 years showed highest RR of cumulative effects on mumps on lag 0-14 d among all age groups at high temperature (25.4℃, 20.1℃) and low temperature (-5.2℃, 1.7℃). With the relative humidity of 66% and 69%, the corresponding RRs were 1.26 (1.01-1.57) and 1.34 (1.02-1.76), respectively, suggesting elevated risks for mumps.
Conclusion The increasing incidence of mumps is associated with both low and high temperatures. The effect of low temperature on reported mumps lasts longer than the effect of high temperature. The children aged 6-14 years are susceptible to mumps. Moreover, the relative humidity of 66%-69% might increase the risk of mumps.
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