Increased Risk of Influenza Infection During Cold Spells in China: National Time Series Study.

Area of Science:

• Environmental Health
• Epidemiology
• Public Health

Background:

• Previous studies indicate adverse effects of cold events on influenza transmission.
• Key factors like cold spell characteristics and regional disparities in their impact on influenza remain under-investigated.

Purpose of the Study:

• To systematically evaluate the association between cold spells and influenza incidence across mainland China.
• To explore how cold spell characteristics and regional socioeconomic factors modify this association.

Main Methods:

• Utilized daily influenza surveillance data from 325 sites in China (2014-2019).
• Employed 15 definitions of cold spells based on temperature thresholds and duration.
• Applied distributed lag linear models and meta-regressions to analyze short-term effects and regional/socioeconomic modifications.

Main Results:

• Cold spells significantly increased influenza risk (Relative Risk: 3.35).
• Impacts were more pronounced with higher temperature thresholds and during the mid-cool season.
• The Jiangnan region showed heightened vulnerability (RR: 7.36), and effects correlated with urban population density, GDP, and urbanization.

Conclusions:

• Cold spells impose a considerable health burden on seasonal influenza in China.
• Regional and socioeconomic variations in cold spell impacts necessitate tailored public health strategies.
• Findings can inform the development of region-specific policies to mitigate influenza risks associated with cold weather.