Many respiratory viruses run rampant in colder months and wane in summer, including influenza and SARS. But will the spread of COVID-19 follow a similar seasonal pattern?
Experts have not found enough scientific evidence that heat and humidity will slow down the virus.
"The COVID-19 virus can be transmitted in all areas, including areas with hot and humid weather," the World Health Organization pointed out in a recent report, indicating that high temperatures have not managed to curb the virus' spread.
As Tom Kotsimbos, associate professor at Australia's Monash University and respiratory physician at the Alfred Hospital in Melbourne, told the Guardian, as this is a new virus, it "does not mean it will be like the others."
"It's interesting that (COVID-19) has spread all over the world quite quickly -- both north and south," he said, adding that the phenomenon suggests either the transmission of the new virus does not rely on temperature or that dependency is not important for its spread.
Though researchers are trying to dig out the relationship between the spread of COVID-19 and temperature, some have already drawn contradictory conclusions.
According to an article published April 2 on the medical journal The Lancet, researchers from the Public Health School of Hong Kong University found an inverse correlation between the temperature and the stability of the virus.
The virus is highly stable at 4 degrees Celsius and could be incubated for up to 14 days; with the incubation temperature increased to 70 degrees Celsius, the time for virus inactivation was reduced to 5 minutes, the researchers said.
By contrast, an article published April 8 on the European Respiratory journal said that researchers from China's Fudan University had found little association of COVID-19 transmission with temperature or UV radiation in Chinese cities.
By analyzing the cumulative number of cases in 224 cities with no fewer than 10 cases as of March 9, the basic reproduction number for 62 cities with over 50 cases as of Feb. 10, and meteorological data such as temperature, humidity, and UV radiation, the scientists concluded that "ambient temperature has no significant impact on the transmission ability of SARS-CoV-2."
"This is quite similar with MERS epidemic in the Arabian Peninsula where MERS cases continue when temperature are 45 degrees Celsius," they said.
Zhu Yifang, associate professor of environmental health sciences at the University of California, Los Angeles, told Xinhua that as related data in the studies are limited, it is uncertain whether the results can be globally verified.
Meanwhile, the possibility cannot be ruled out that the coming hot spells in the Northern Hemisphere might reduce the virus, Zhu said, adding that it also remains unknown whether the pandemic will stage a comeback during winter, becoming seasonal.