The global coronavirus pandemic that has killed thousands,
infected over 350,000 and sent major economies into a tailspin may be slowed by
the upcoming changing of the seasons, several preliminary studies suggest.
However, the research on how the novel coronavirus behaves in various
temperature and humidity levels is only just getting underway.
A warm and humid weather is linked to slower spread of the novel coronavirus,
according to a study which suggests that Asian countries experiencing monsoon
may experience lesser transmission of the virus.
The scientists, including Qasim Bukhari from the Massachusetts Institute of
Technology (MIT) in the US, assessed data on the number of COVID-19 infections
in different parts of the world and compared it with two parameters of weather
from all the regions — temperature and humidity.
The findings, described in SSRN repository, show that 90 per cent of the novel
coronavirus, SARS-CoV-2, transmissions until March 22, 2020 have occurred in
regions with temperature between 3 and 17 degrees Celsius.
They added that these regions also had between 4 to 9 gram per cubic metre
(g/m3) of absolute humidity — a measure of the amount of water vapour per
cubic metre of atmosphere.
According to the MIT scientists, the total number of cases in countries with
mean temperature greater than 18 degree Celsius and absolute humidity more than
9 g/m3 in January-February-early March is less than 6 per cent.
Based on their analysis, the scientists noted that Asian countries experiencing
monsoon may see a slowdown in transmission as absolute humidity is generally
above 10g/m3 during monsoon.
“Within the US, the outbreak also shows a north-south divide. Northern (cooler)
states have much higher growth rates compared to southern (warmer) states. The
spread of 2019-nCoV has been limited in Texas, New Mexico and Arizona,”
they reported in the study.
Even in California, which spans a large climatic zone, the scientists said, the
number of cases is double in the northern part of the state than in its south.
“Within the US, Oregon and Louisiana are two outliers, with Oregon having less
than 200 cases even though it is straddled between the hotspots of California
and Washington and Louisiana having approximately 1,000 cases by March 22 2020,
even though it is relatively warm and humid,” the researchers said.
They said the overall growth rate is lower in many parts of Asia, Middle
eastern, and South American countries even though the countries in these
regions have not implemented drastic quarantine measures such as those in
China, Europe and some US states.
While it could be argued that there may be lower number of testings such as in
India, Pakistan, Indonesia and African countries, the researchers said, many
countries like Singapore, UAE, and Saudi Arabia, have performed more 2019-nCoV
tests per million people than US, Italy, and several European countries.
Based on this observation, they suggested that non-testing is not an issue at
least for the countries listed above, and that many of these countries are also
global travel hubs with thousands of people entering and exiting the country
everyday.
Citing these factors, the researchers argued that factors other than mobility
and quarantining might play an important role in slowing the transmission of
the virus.
“With more than 10,000 cases being reported in regions with mean temperature
above 18 degree Celsius after March 15, the role of warmer temperature in
slowing the spread of the 2019-nCoV as suggested previously, might only be
observed, if at all, at much higher temperatures,” the scientists wrote in
the study.
However, the scientists cautioned that there are several unknowns in the data
currently used to arrive at the conclusion.
“Our conclusions are based on currently available data with several unknowns
including how the virus is mutating and evolving, case fertility ratio,
reproductive numbers and direct versus indirect transmissions,” they said.
The researchers also emphasised that the results “in no way suggest that
2019-nCoV would not spread in warm humid regions.”
They said effective public health interventions should be implemented across
the world to slow down the transmission of 2019-nCoV.
Warm, Humid Weather Could Slow Coronavirus, New Research Finds
