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Sci Total Environ. 2019 Oct 31;703:134727. doi: 10.1016/j.scitotenv.2019.134727. [Epub ahead of print] Latitudes mediate the association between influenza activity and meteorological factors: A nationwide modelling analysis in 45 Japanese prefectures from 2000 to 2018.
Chong KC1, Liang J2, Jia KM3, Kobayashi N4, Wang MH5, Wei L2, Lau SYF6, Sumi A7.
Author information
1 JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China; Clinical Trials and Biostatistics Laboratory, Shenzhen Research Institute, The Chinese University of Hong Kong, China. Electronic address: marc@cuhk.edu.hk. 2 JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China. 3 JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China. Electronic address: 1155078733@link.cuhk.edu.hk. 4 Department of Hygiene, Sapporo Medical University School of Medicine, Sapporo, Japan. Electronic address: nkobayas@sapmed.ac.jp. 5 JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China; Clinical Trials and Biostatistics Laboratory, Shenzhen Research Institute, The Chinese University of Hong Kong, China. Electronic address: maggiew@cuhk.edu.hk. 6 JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China. Electronic address: stevenlau@cuhk.edu.hk. 7 Department of Hygiene, Sapporo Medical University School of Medicine, Sapporo, Japan. Electronic address: sumi@sapmed.ac.jp.
Abstract
BACKGROUND:
Cold and dry conditions were well-documented as a major determinant of influenza seasonality in temperate countries but the association may not be consistent when the climate in temperate areas is closer to that in sub-tropical areas. We hypothesized latitudes may mediate the association between influenza activity and meteorological factors in 45 Japanese prefectures.
METHODS:
We used the weekly incidence of influenza-like illness of 45 prefectures from 2000 to 2018 as a proxy for influenza activity in Japan, a temperate country lying off the east coast of Asia. A combination of generalized additive model and distributed lag nonlinear model was adopted to investigate the associations between meteorological factors (average temperature, relative humidity, total rainfall, and actual vapour pressure, a proxy for absolute humidity) and the influenza incidence. Kendall's tau b (τ) and Spearman correlation coefficient (rs) between latitude and the adjusted relative risk (ARR) of each meteorological factor were also assessed.
RESULTS:
A higher vapour pressure was significantly associated with a lower influenza risk but the ARR strongly weakened along with a lower latitude (τ = -0.23, p-value = 0.02; rs = -0.33, p-value = 0.03). Lower temperature and lower relatively humidity were significantly associated with higher influenza risks in over 65% and around 40% of the prefectures respectively but the strength and significance of the correlations between their ARRs and latitude were weaker than that from vapour pressure.
CONCLUSION:
Even though the range of latitudes in Japan is small (26?N-43?N), the relationships between meteorological factors and influenza activity were mediated by the latitude. Our study echoed absolute humidity played a more important role in relating influenza risk, but we on the other hand showed its effect on influenza activity could be hampered in a low-latitude temperate region, which have a warmer climate. These findings thus offer a high-resolution characterization of the role of meteorological factors on influenza seasonality.
Copyright ? 2019 Elsevier B.V. All rights reserved.
KEYWORDS:
Humidity; Influenza; Japan; Latitude; Temperature
PMID: 31731153 DOI: 10.1016/j.scitotenv.2019.134727