key: cord-317138-6nonzjbq
authors: Takagi, Hisato; Kuno, Toshiki; Yokoyama, Yujiro; Ueyama, Hiroki; Matsushiro, Takuya; Hari, Yosuke; Ando, Tomo
title: The higher temperature and ultraviolet, the lower COVID-19 prevalence – Meta-regression of data from large U.S. cities
date: 2020-06-20
journal: Am J Infect Control
DOI: 10.1016/j.ajic.2020.06.181
sha: 
doc_id: 317138
cord_uid: 6nonzjbq

nan

To the Editor:

Higher temperature and ultraviolet (UV) index in Northern Europe have been reported as the most important meteorological protective factors for the transmission of influenza virus. 1 On the other hand, a recent study in China suggests that higher temperature and UV radiation may not be associated with a decrease in the epidemics of Coronavirus disease 2019 (COVID-19). 2 To determine whether prevalence of COVID-19 is modulated by meteorological conditions, we herein conducted meta-regression of data from large U.S. cities.

We selected 33 large U.S. cities with a population of >500,000 in 2010 from U.S. Census Bureau (http://www.census.gov). We obtained 1) integrated number of confirmed COVID-19 cases in the county (to which the city belongs) on 14 May 2020 from Johns Hopkins Coronavirus Resource Center (https://coronavirus.jhu.edu), 2) estimated population in 2019 in the county from U.S. Census Bureau, and 3) monthly meteorological conditions at the city for 4 months (from January to April 2020) from National Weather Service (https://www.weather.gov), World Weather Online (https://www.worldweatheronline.com), and Global Solar Atlas (https://globalsolaratlas.info/map) ( Table 1) . As the meteorological conditions, 1) mean temperature (F), total precipitation (inch), mean wind speed (mph), mean sky cover, and mean relative humidity (%) were available from National Weather Service;

2) mean pressure (mb), mean UV index, and total sun hours were obtainable from World Weather Online; and 3) total solar direct normal irradiation (DNI) (kWh/m 2 ) in the average year was procurable from Global Solar Atlas. Monthly data for the 4 months (mean pressure/UV index and total sun hours were available for 3 months, from January to March 2020) were averaged or cumulated. The COVID-19 prevalence was defined as the integrated number of COVID-19 cases divided by the population.

Random-effects meta-regression was performed by means of OpenMetaAnalyst (http://www.cebm.brown.edu/openmeta/index.html).

In a meta-regression graph, COVID-19 prevalence (plotted as logarithm transformed prevalence on the y-axis) was depicted as a function of given factors (plotted as meteorological data on the x-axis).

Results of the meta-regression were summarized in Table 2 The present meta-regression suggests that temperature, UV index, sun hours, and solar DNI may be negatively, and wind speed and sky cover may be positively associated with COVID-19 prevalence. Higher sun hours/solar DNI and lower sky cover are probably related to higher UV radiation. Despite the association of lower temperature and UV-index with the influenza transmission, 1 no association of temperature and UV radiation with the COVID-19 epidemics has been reported, 2 however, which may be denied by the present results of the association of higher temperature/UV index/sun hours/solar DNI and lower sky cover with lower COVID-19

prevalence. In conclusion, higher temperature/UV index/sun hours/solar DNI and lower wind speed/sky cover may be associated with lower COVID-19 prevalence (i.e.

lower temperature/UV index/sun hours/solar DNI and higher wind speed/sky cover may be associated with higher COVID-19 prevalence), which should be confirmed by further epidemiological researches adjusting for various risk and protective factors (in addition to meteorological conditions) of COVID-19.

None. 

Low Temperature and Low UV Indexes Correlated with Peaks of Influenza Virus Activity in Northern Europe during

No association of COVID-19 transmission with temperature or UV radiation in Chinese cities