The novel coronavirus is seasonal and spreads in certain climate conditions, a new study suggests.
Researchers found that areas affected early on in the outbreak were on a similar band of northern latitude, such as Wuhan and Daegu in Asia; Milan and Paris in Europe; and Seattle in the US.
Also related among these cities were ranges of cold temperatures and relatively low humidity from January through March.
This seems to imply that the virus behaves similarly to seasonal respiratory viruses such as the flu.
The team, from the University of Maryland School of Medicine, says its maps can help scientists and policy makers predict where and when outbreaks will occur so they can stop the deadly disease in its tracks before it’s too late.
From November 2019 to March 2020, eight cities that had ‘substantial’ spread of coronavirus were all on a narrow band of latitudes between 30° N and 50° N (in green band and black circles)
This combination of low temperatures puts Central Asia, the Caucuses, Eastern and Central Europe, the UK, the northeastern and midwestern US, and British Columbia (all in green band) at the highest risk for spread during the fall and winter
For the study, published in JAMA Network Open, the team collected climate data from 50 cities around the world between January 2020 and March 2020.
Eight cities with ‘substantial’ spread of the virus – Daegu, South Korea; Madrid, Spain; Milan, Italy; Paris, France; Qom, Iran; Seattle, USA; Tokyo, Japan; and Wuhan, China – were compared to 42 cities that were affected little to none by the virus.
‘Substantial’ transmission was defined as a country reporting at least 10 deaths from COVID-19, the disease caused by the virus, by March 10.
Climate data, such as temperatures and humidity, came from the European Centre for Medium-Range Weather Forecasts ERA-5 reanalysis.
From November 2019 to March 2020, the eight cities that had substantial spread were all on a narrow band of latitudes between 30° N and 50° N.
However, COVID-19 was unsuccessful in spreading as widely among cities north of this band such as in Moscow, Russia, which sits at 56.0° N, and south such as in Bangkok, Thailand, sitting at 13.7° N.
The cities that had substantial spread also had low levels of specific humidity, or how much water vapor is in a unit of moist air in grams per kilograms (above)
Researchers then looked at 2-m temperature, which is the temperature near Earth’s surface, where the majority of human activity takes place.
Results showed that in January 2020 in Wuhan and in February 2020 in the other seven cities, the average temperature at airport weather stations was between 39F (4C) and 48F (9C).
Average temperatures 20 to 30 days before the first community death in each city were roughly the same, ranging from 37F (3C) to 48F (9C).
The cities also had similar low amounts of specific humidity (Q), or how much water vapor is in a unit of moist air in grams per kilograms.
‘Having low average temperatures and low Q tightly clustered the cities with substantial outbreaks as of March 10, 2020, compared with cities that did not have COVID-19 cases,’ the authors wrote.
The team says the findings show why the risk of community spread affected areas such as Central Asia, the Caucuses, Eastern and Central Europe, the UK, the northeastern and midwestern US, and British Columbia in the winter.
It also shows that the coronavirus behaves similarly to a seasonal respiratory virus, such as influenza, peaking in cold weather and dying out in warmer ones.
Aside from prolonging the life of the virus, cold temperatures and low humidity could also affect how quickly it breeds in the nasal cavity and impaired immunity, allowing the virus to spread and move throughout the body.
‘All of this points to a potential direct association between temperature and SARS-CoV-2 environmental survival and spreading,’ the authors concluded.
‘Using weather modeling, it may be possible to estimate the regions most likely to be at a higher risk of substantial community spread of COVID-19 in the upcoming weeks, allowing for concentration of public health efforts on surveillance and containment.’
In the US, there are more than two million confirmed cases of the virus and more than 112,000 deaths.
