Digging deeper, Yao’s group conducted a complex analysis of the spread of novel coronavirus across China, including Hubei province, where the global pandemic began. They compared that epidemiological data to fluctuations in daily temperatures and the amount of sunlight, as well as changes in humidity.
Reporting April 9 in the European Respiratory Journal, the Chinese team found that, after adjusting for humidity and UV levels, “the spread ability of COVID-19 would not change with increasing temperature.” Likewise, adjusting for temperature and humidity, the amount of UV sunlight also didn’t affect transmission rates.
The team pointed out that these patterns are similar to what was seen with another coronavirus-linked outbreak, the spread in 2012 to 2013 of Middle East respiratory syndrome (MERS). In that outbreak, MERS cases still spread even when outside temperatures in the Arabian Peninsula soared to 113 degrees Fahrenheit.
“Other newly emergent zoonotic [originating in animals] disease, such as Ebola or pandemic strains of influenza, have also occurred in unpredictable patterns,” the scientists noted.
Yao’s team stressed, however, that their study is not definitive, and “certainly, further studies with longer follow-up period and wider temperature range are warranted.”
For its part, the NAS agreed. “Additional studies as the pandemic unfolds could shed more light on the effects of climate on transmission,” the institute said in a news release. But right now, their own “expert consultation” on the potential seasonality of COVID-19 finds little conclusive evidence that cases will drop as the summer nears.
“There is some evidence to suggest that the COVID-19 virus may transmit less efficiently in environments with higher ambient temperature and humidity; however, given the lack of immunity to the virus globally, this reduction in transmission efficiency may not lead to a significant reduction in disease spread without the simultaneous adoption of major public health interventions,” the NAS said.
Dr. Miriam Smith is chief of infectious disease at Long Island Jewish Forest Hills, in New York City. Reading over the Chinese study, she agreed that other factors — not the approach of summer — may finally curb the COVID-19 pandemic.
“Until herd immunity is established, effective evidence-based treatments become available and a vaccine is developed, social distancing will likely continue to play a role in reducing transmission,” Smith said.
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