June 11 (UPI) -- SARS-CoV-2 behaves like a "seasonal" virus that spreads more rapidly in cooler temperatures and drier, less humid climates, according to an analysis published Thursday by JAMA Network Open.
Instead of thriving in the tropical environs of southeast Asia, as expected, the new coronavirus, which causes the disease COVID-19, exploded in eight cities located "on a narrow band, roughly on the 30 degrees north to 50 degrees north corridor" latitude, the international team of researchers observed.
Temperatures in these cities ranged from 41 to 51 degrees during the period of highest virus spread, with relative humidity readings between 44 and 84 percent, they said.
"We think the SARS-CoV-2 virus has a more difficult time spreading in conditions with higher temperature and humidity," study co-author Dr. Mohammad Sajadi, an associate professor in the University of Maryland School of Medicine's Institute of Human Virology, told UPI.
Based on the findings, "we believe that the study of the climate can help predict outbreaks and/or hot spots, and that this factor should be incorporated into future epidemiologic models," Sajadi said. "However, we think further work should be done to refine the climate model."
Although much of the United States already is experiencing warmer, more humid summer weather, most of the country -- Alaska being the exception -- lies within the "narrow band" identified by Sajadi and his colleagues.
For their study, the researchers examined climate data from 50 cities worldwide with and without "substantial community spread" of COVID-19.
Eight cities with substantial spread of COVID-19 as of March 10 -- Wuhan, China; Tokyo; Daegu, South Korea; Qom, Iran; Milan; Paris; Seattle; and Madrid -- were compared with 42 cities with no confirmed cases or low community spread.
All of the eight cities with substantial community spread as of March 10 were located between 30 and 50 degrees north latitude, which roughly equates to the southern and northern borders of the continental United States, the authors found. These cities "had consistently similar weather patterns," they said.
The analysis also revealed "a lack of substantial community establishment in expected locations" based on geographic proximity, according to the researchers. For example, while Wuhan, China -- at 30.8 degrees north -- had more than 80,000 cases as March 10, Hanoi, Vietnam -- 21.2 degrees north -- had 31 cases.
"In studying the earliest stages of the COVID-19 pandemic, the disease did not spread like was initially predicted," Sajadi said.
Instead, "the distribution of significant community outbreaks along restricted latitude, temperature and humidity were consistent with the behavior of a seasonal respiratory virus," he said.
"We think the SARS-CoV-2 virus has a more difficult time spreading in conditions with higher temperature and humidity, [but] the best way to test this hypothesis is to study it in the laboratory where these conditions can be controlled," Sajadi said.