TY - JOUR
T1 - The joint impact of temperature, humidity, and air pollution on COVID-19 incidence
T2 - a multi-country time-series study in 439 cities
AU - Wagatsuma, Keita
AU - Feurer, Denise
AU - Yu, Wenhua
AU - Xu, Rongbin
AU - Riffe, Tim
AU - Kniffka, Maxi Stella
AU - Acosta, Enrique
AU - Armstrong, Ben
AU - Mistry, Malcolm
AU - Lowe, Rachel
AU - Royé, Dominic
AU - Hashizume, Masahiro
AU - Tobias, Aurelio
AU - Vicedo-Cabrera, Ana Maria
AU - Madaniyazi, Lina
AU - Sheng Ng, Chris Fook
AU - Íñiguez, Carmen
AU - Ragettli, Martina S.
AU - Lavigne, Eric
AU - Correa, Patricia Matus
AU - Ortega, Nicolás Valdés
AU - Kyselý, Jan
AU - Urban, Aleš
AU - Orru, Hans
AU - Indermitte, Ene
AU - Maasikmets, Marek
AU - Breitner-Busch, Susanne
AU - Schneider, Alexandra
AU - Honda, Yasushi
AU - Alahmad, Barrak
AU - Zanobetti, Antonella
AU - Schwartz, Joel
AU - Carrasco, Gabriela
AU - Holobâca, Iulian Horia
AU - Kim, Ho
AU - Lee, Whanhee
AU - Bell, Michelle L.
AU - Scovronick, Noah
AU - Acquaotta, Fiorella
AU - de Sousa Zanotti Stagliorio Coelho, Micheline
AU - Diaz, Magali Hurtado
AU - Félix Arellano, Eunice Elizabeth
AU - Michelozzi, Paola
AU - Stafoggia, Massimo
AU - de’Donato, Francesca
AU - Rao, Shilpa
AU - Seposo, Xerxes
AU - Tong, Shilu
AU - Klompmaker, Jochem
AU - Guo, Yuming
AU - Masselot, Pierre
AU - Gasparrini, Antonio
AU - Sera, Francesco
N1 - Publisher Copyright:
© 2026 The Author(s).
PY - 2026/2
Y1 - 2026/2
N2 - Several studies have explored the short-term effects of environmental stressors on coronavirus disease 2019 (COVID-19) transmission and severity. However, evidence on the interactive effects of meteorological conditions and air pollution remains limited and geographically variable. We therefore aimed to quantify the independent and interactive effects of short-term exposure to humidex, a composite index of temperature and relative humidity, and fine particulate matter ≤ 2.5 μm (PM2.5) on daily COVID-19 incidence across multiple cities and in multiple countries. Daily time-series data on confirmed COVID-19 cases, meteorological factors, and PM2.5 concentrations were collected from 439 cities in 22 countries during January 2020–August 2022 as part of the Multi-Country Multi-City Collaborative Research Network. A two-stage design was applied: first, city-specific quasi-Poisson models with distributed lag non-linear models estimated exposure–response associations; second, multilevel random-effects meta -analyses pooled city-specific estimates. Effect modification by PM2.5 was assessed using a product term between non-linear humidex function and linear PM2.5 function. Approximately 95.1 million confirmed COVID-19 cases were analyzed. Lower humidex values (0.1 °C versus 15.1 °C) were associated with increased daily cases (relative risk [RR]: 1.1192, 95% confidence interval [CI]: 1.0214–1.2262). A 10 μg/m3 increase in PM2.5 over the current and preceding 2 days was associated with a modest increase in daily cases (RR: 1.0079, 95% CI: 1.0001–1.0161). No statistically significant interaction between humidex and PM2.5 was observed. Short-term exposure to cold–dry conditions and elevated PM2.5 independently increased COVID-19 incidence, highlighting the need to consider both thermal environment and air quality when designing climate-resilient public health responses. These findings enhance understanding of how climate-related environmental stressors influence COVID-19 transmission.
AB - Several studies have explored the short-term effects of environmental stressors on coronavirus disease 2019 (COVID-19) transmission and severity. However, evidence on the interactive effects of meteorological conditions and air pollution remains limited and geographically variable. We therefore aimed to quantify the independent and interactive effects of short-term exposure to humidex, a composite index of temperature and relative humidity, and fine particulate matter ≤ 2.5 μm (PM2.5) on daily COVID-19 incidence across multiple cities and in multiple countries. Daily time-series data on confirmed COVID-19 cases, meteorological factors, and PM2.5 concentrations were collected from 439 cities in 22 countries during January 2020–August 2022 as part of the Multi-Country Multi-City Collaborative Research Network. A two-stage design was applied: first, city-specific quasi-Poisson models with distributed lag non-linear models estimated exposure–response associations; second, multilevel random-effects meta -analyses pooled city-specific estimates. Effect modification by PM2.5 was assessed using a product term between non-linear humidex function and linear PM2.5 function. Approximately 95.1 million confirmed COVID-19 cases were analyzed. Lower humidex values (0.1 °C versus 15.1 °C) were associated with increased daily cases (relative risk [RR]: 1.1192, 95% confidence interval [CI]: 1.0214–1.2262). A 10 μg/m3 increase in PM2.5 over the current and preceding 2 days was associated with a modest increase in daily cases (RR: 1.0079, 95% CI: 1.0001–1.0161). No statistically significant interaction between humidex and PM2.5 was observed. Short-term exposure to cold–dry conditions and elevated PM2.5 independently increased COVID-19 incidence, highlighting the need to consider both thermal environment and air quality when designing climate-resilient public health responses. These findings enhance understanding of how climate-related environmental stressors influence COVID-19 transmission.
KW - COVID-19
KW - Effect modification
KW - Humidex
KW - MCC Collaborative Research Network
KW - PM
KW - Two-stage design
UR - https://www.scopus.com/pages/publications/105029027309
U2 - 10.1016/j.envint.2026.110090
DO - 10.1016/j.envint.2026.110090
M3 - Article
C2 - 41621133
AN - SCOPUS:105029027309
SN - 0160-4120
VL - 208
SP - 110090
JO - Environment international
JF - Environment international
M1 - 110090
ER -
ODS 3: Salud y bienestar
ODS 11: Ciudades y comunidades sostenibles