Effects Of Temperature And Relative Humidity On Hand,Foot And Mouth Disease In Ningbo City During 2014-2016

Objective: There is a particular correlation between meteorological factors and epidemics of hand,foot and mouth disease(HFMD).Since the impact of meteorological factors on the risk of HFMD is regionally different,it is important to positively explore such impact in Ningbo based on big data in order to guide the preventive and control measures better,thus protecting the public health.Methods: The HFMD surveillance data of Ningbo from January 1,2014 to December 31,2016 were collected from the China Information System for Diseases Control and Prevention(CISDCP),and the meteorological data of the same period were collected from the Ningbo Meteorological Bureau.The epidemiological characteristics of HFMD was analyzed first.And then the distributed lag non-linear model(DLNM)based on Poisson distribution was used to analyze the impact of the two major meteorological effects,daily average temperature and daily average relative humidity(RH),on the risk of HFMD at different percentiles.The effects of these factors were further analyzed by gender,age group and occupation.Results:1.The total report cases of HFMD in Ningbo were 104559 during 2014-2016,as the annual reported incidence rate was 561.71/105,305.09/105,487.09/105,respectively.It is obviously that HFMD had a seasonality,with the main peak in April to July and the second small peak in October to December.Most cases occurred in children aged 1 to 4 years old,accounting for 80.79% of the total incidence.The gender ratio was 1.45.60.55% of the total reported cases was scattered children,followed by child-care children,accounting for 35.12%.The enterovirus Cox A16 was predominant in recent years according to the laboratory analysis.2.The influence of daily temperature and daily relative humidity on the risk of HFMD was nonlinear and lagged.The maximum time lag effect of daily temperature on HFMD was about 14 to 20 days,while the maximum time lag effect of daily relative humidity was 10-14 days.Low temperature was the protective factor for HFMD,with the minimum cumulative RR of 0.324(95%CI: 0.193-0.545)at 3°C,and the minimum intraday RR of 0.908(95%CI: 0.887-0.931)in lag 10d;while high temperature was the risk factor,with the maximum cumulative RR of 1.791(95% CI: 1.542-2.081)at 28°C,and the maximum intraday RR of 1.075(95%CI: 1.054-1.096)in lag 5d.Low relative humidity was protective factor for HFMD,with the minimum cumulative RR of 0.638(95%CI:0.546-0.744)at RH=48%,and the minimum intraday RR of 0.908(95% CI: 0.887-0.931)in lag 7d;while high RH performed the risk factor,with maximum intraday RR of 1.029(95%CI:1.013-1.045)at RH=88% in lag 6d.However,the effects of extreme high relative humidity(RH P97.5=97%)on HFMD were not statistically significant.3.There was an interaction between daily average temperature and daily average relative humidity.By adding relative humidity to the multi-factor model,the influence of low temperature on the onset of HFMD was weakened,but the duration was increased;while the influence of high temperature on HFMD was enhanced,but the duration was similar.Nevertheless,the impact of relative humidity on the onset of HFMD was weakened,but the duration did not change significantly when affected by the temperature in multi-factor mode.It could be considered that the impact of temperature was greater and unstable;and the impact of relative humidity was weak and relatively stable.4.The effects of daily average temperature and daily average relative humidity on HFMD were different among different genders,ages,and occupations.Among them,girls,0-4 years old and scattered children were at high-risk,which were mainly affected by the interaction of high temperature and relative humidity.Conclusions: The daily average temperature and the daily average relative humidity had delayed effects and interactive effects on the risk of HFMD.The effect of temperature was greater than relative humidity.In this study,high temperature(28°C)and high relative humidity(RH=88%)had the greatest impact on girls,0-4 years old,and scattered children.It is recommended that relevant departments should strengthen publicity and education,and take prevent and control measures positively.