Objective To analyze the relationship between daily mean temperature and daily incidents of influenza in Lanzhou city and to provide evidences for influenza prevention and control.
Methods We collected data on daily influenza incidents reported during the period from 2008 to 2017 among residents of Lanzhou city and on daily temperature of same period. Then we analyzed the data using time series model and distributed lag non-linear time series model (DLNM) to explore the association of daily mean temperature with influenza incidents.
Results During the period in the city, a total of 4 866 influenza cases were reported; the male to female ratio of the cases was 1.21 and 34.03% of the cases were children aged 6 – 14 years. A non-linear correlation was found between the daily mean temperature and daily influenza incidents; there were the strongest lag 12-day effect of low daily temperature of – 3 ℃, with a relative risk (RR) of 1.23 (95% confidence interval 95% CI: 1.09 – 1.37), and the strongest lag one day effect of high daily temperature of 33 ℃ (RR = 2.70, 95% CI: 0.41 – 17.66) on daily influenza incidents in comparison to the influence of mean annual daily temperature of 11.22 ℃. The M shaped plot depicting the relationship between RR of influenza incidents and lag days of the effect of daily temperature was observed for both the daily low temperature (– 5.2 ℃ and 2.1 ℃) and high temperature (20.1 ℃ and 25.4 ℃). A significant accumulative effect of low daily temperature of – 5.2 ℃ was observed among all the residents at lag 14-day and the effect was the strongest for the children aged 6 – 14 years (RR = 1.79, 95% CI: 1.08 – 3.99); while, the accumulative effect of high temperature of 20.1 ℃ was of significance among all the residents from the lag day 3 to the lag day 7 and the effect was also the strongest for the children aged 6 – 14 years, with the RR of 6.45 (95% CI: 3.21 – 9.23).
Conclusion Low and high daily temperature associate with increased risk of influenza incidents among residents of Lanzhou city; the accumulative effect of high daily temperature is stronger than that of low daily and lag duration for the effect of low temperature is longer than that of high temperature; the children aged 6 – 14 years are most susceptible to the effect of low and high daily temperature.
DownLoad: