Quantifying the impact of ambient temperature on varicella incidence: Evidence from a meta-analysis.

BACKGROUND

Varicella is a significant global health burden, yet the specific impact of ambient temperature on varicella incidence remains insufficiently understood. This study aims to quantify the association between ambient temperature and varicella risk through a systematic review and meta-analysis.

METHODS

We conducted a comprehensive meta-analysis of studies from PubMed, Embase, Web of Science, and CNKI databases (up to January 7, 2025). We included studies that assessed temperature effects on varicella incidence and excluded those on animals, serology, reviews, or unpublished data. Using a random-effects model, we pooled relative risks (RRs) for a 1 °C increase in ambient temperature and performed heterogeneity assessments (q, τ2, I2). Subgroup and sensitivity analyses were conducted based on climate zone, sex, age group, and methodological adjustments. Publication bias was evaluated via funnel plots and Egger's test, and study quality was assessed according to STROBE guidelines. The protocol was registered with PROSPERO (CRD420251003054).

RESULTS

From 2389 records screened, 14 studies with approximately 1.4 million varicella cases were included. A 1 °C increase in temperature was associated with a 4 % reduction in varicella risk (RR = 0.96; 95 % CI: 0.93-0.98; I2 = 97.6 %; 95 % PI: 0.86-1.07). Subgroup analyses revealed a stronger association in temperate regions (RR = 0.91; 95 % CI: 0.84-0.98) and among school-aged children (RR = 0.93; 95 % CI: 0.91-0.96). Sensitivity analyses confirmed the robustness of these findings.

CONCLUSIONS

This study suggests that higher ambient temperatures are associated with lower varicella incidence, particularly in temperate regions and among school-aged children. These findings provide insight into climate-driven varicella dynamics, particularly in the context of future global warming, and can inform climate-sensitive public health strategies and resource allocation.