Ideal weather conditions may have helped coronavirus thrive initially, study suggests
By
Mark Puleo, AccuWeather staff writer
Published May. 19, 2020 11:48 AM
A coronavirus lockdown has been imposed in a second city in China this week.
With the United States set for the unofficial beginning of summer over Memorial Day weekend, and the solstice following about a month later for the Northern Hemisphere, a recently published study from China may provide further insight into how weather, particularly summery conditions, may affect the spread of the new coronavirus.
The publication from researchers at Chengdu University of Information Technology in China analyzed the monthly average temperature, specific humidity and downward short-wave ultraviolet radiation in each Chinese province during the early days of the coronavirus outbreak.
The new study is the latest in a string of similar studies published in recent months that analyze how weather conditions might impact the spread of SARS-CoV-2, the pathogen that causes COVID-19.
The Chengdu researchers said the applications of the findings they came away with are incomplete, but the results suggest that numerous suitable weather factors may have laid an ideal foundation for the virus to take root and eventually spread throughout the world.
Using data from the European Center for Long-Term Weather Forecast (ECMWF), they compared the weather conditions with the number of confirmed cases from each province in China in January and February. According to the findings, there are three critical meteorological conditions in which SARS-CoV-2 can most effectively spread.
The first is temperature. The researchers said the analysis "showed that COVID-19 cases were concentrated in the provinces with temperatures in [the] range of 0–10 degrees Celsius," or 32 to 50 degrees Fahrenheit.
Workers wearing face masks and gloves serve lunch at a staff cafeteria in a semiconductor production facility for Renesas Electronics during a government-organized tour for journalists in Beijing, Thursday, May 14, 2020. (AP Photo/Mark Schiefelbein)
Increased humidity and UV light from the sun are the other two critical factors the researchers cited.
The researchers reported that the strength of solar radiation also may have an effect on how the virus spreads. Places where solar radiation remained below a certain level saw more effective spread, according to their findings. Meanwhile, higher-elevation locations, which see stronger amounts of UV rays due to their altitude, along with places that have drier climates, and therefore fewer clouds in the sky to diminish solar radiation, saw less transmission.
"The Qinghai-Tibet Plateau has a high altitude (approximately 4,000 m) and is subjected to strong solar radiation, resulting in a higher amount of UV-B radiation reaching the surface," the researchers wrote about a vast area covering 965,000 square miles of southwest China. The Qinghai-Tibet Plateau is about three miles above sea level and is nicknamed the "Roof of the World."
In the left (January) and right (February) columns, researchers tracked data for temperature (a and b), UV radiation (c and d) and humidity (e and f).
It's not just altitude that affects solar radiation. The number and thickness of clouds in the sky can also determine how much of the downward shortwave ultraviolet radiation -- energy emitted by the sun -- reaches the Earth's surface.
"The weather in the arid region of the Northwest is clear with fewer clouds, and the radiation received on the surface is higher than in other parts of China," the researchers wrote in the study. "As a result, it may be difficult for COVID-19 to spread in the plateau or the arid area in the northwest due to high UV-B radiation."
The study's results show a connection between areas that had lower numbers of cases that sit at higher altitudes and, therefore, received higher levels of UV-B radiation.
In an email to AccuWeather, Xiaohang Wen, the lead author of the study, said their findings don't only apply to China, but to the rest of the world as well.
In the study, the researchers said their findings will not just help the world understand how the virus first grew, but also how to prepare for dealing with it in the future.
"I think the virus is likely to start circulating in South America in July and August, and it will break out again in various countries in the northern hemisphere after October and November (If countries in the northern hemisphere do not adopt stricter prevention and control measures this autumn)," Wen said to AccuWeather.
Previous studies have also focused on those factors, particularly UV radiation. Data compiled by AccuWeather from the beginning of the year demonstrates the steady increase of UV rays in major cities as the calendar moves away from winter. Studies have suggested that a lack of UV radiation or vitamin D from sun exposure could be tied to stronger severity of COVID-19 cases in certain portions of the world.
Transmission electron micrograph of SARS-CoV-2 virus particles, isolated from a patient. Image captured and color-enhanced at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland.
(National Institute of Allergy and Infectious Diseases, NIH)
AccuWeather Meteorologist Michael Steinberg said there are numerous factors that go into determining how much UV radiation reaches the Earth and seasonality plays a crucial role.
"UV radiation is emitted by the sun in a near-constant amount, but the amount that reaches the Earth varies. It is partially blocked by the ozone layer and some kinds of clouds, especially thick ones, and influenced to a lesser degree by pressure, surface elevation, humidity, and several other factors," Steinberg said. "But the most important factors are the latitude, time of day, and time of year – these three determine the maximum possible level of UV – the actual amount is then determined by the other factors."
The Chengdu authors' findings, along with prior studies on the spread of seasonal influenza, show that even just a month of favorable environmental change can greatly reduce transmission.
“A further understanding of the environmental factors that are prevalent in the development of COVID-19 will help predict the potential risks of the global spread of this disease, and provide support for the prevention and surveillance of countries around the world,” they wrote.
A figure of a scatter plot from the published study shows how the number of confirmed cases in a province related to changing meteorological data in January, represented on the left, and February, represented on the right. (papers.ssrn.com)
To conduct their study, the researchers compiled data from January to February in each Chinese province to plot how changes in meteorological conditions correlated with the number of confirmed cases in each province.
In looking to the summer in the United States, Steinberg said humidity levels, temperature and UV radiation will be considerably higher than in the winter, when the outbreak erupted. These factors should greatly reduce transmission if the researchers' conclusions hold true.
"The amount of water vapor in the air (absolute humidity) and the specific humidity are typically much higher in the summer season, because the hotter air can hold more water vapor," Steinberg said. "When the relative humidity (which is what weather reports usually present) is 100% in the winter at a temperature of 30 F, there is only about half as much actual water vapor in the air as in the summer when the relative humidity is 25% but the temperature is 84 F."
In addition to a rise in humidity, the amount of solar radiation also increases significantly in the U.S. during summer, Steinberg explained.
"The seasonal variation is much greater at higher latitudes," he said, "but on average across the United States, the daily high UV Index level might be 8-9 in the summer and 2-3 in the winter."
The Chengdu team referenced prior studies that have shown that most enveloped viruses — such as coronaviruses — exhibit strong seasonality due to the hardening of the virus particle’s oily coating.
Warmer and more humid conditions are expected to soften that oily coating and make respiratory droplets fall to the ground more quickly, rather than lingering in the air.
A security worker, wearing a face mask, stands guard at the Disneyland theme park in Shanghai as it reopened Monday, May 11, 2020. With warmer weather and new coronavirus cases and deaths falling to near-zero, China has been reopening tourist sites such as the Great Wall and the Forbidden City palace complex in Beijing.(AP Photo/Sam McNeil)
Dr. Jeremy Rossman of Kent University previously told AccuWeather that he expects the summer months in the U.S. to help with slowing transmission due to the impact higher humidity levels have on respiratory droplets.
"As the country starts to have higher levels of humidity, we might see a small reduction in virus transmission," he said. "That might be really beneficial in terms of containment measures, but it shouldn't be enough that it would actually stop the virus on its own."
While the authors of the study added that many other factors, such as population flow, were not analyzed in this research, they argued that meteorological data points and weather patterns should be a focal point in future studies in order to better paint a full picture of COVID-19's scope.
"Although there are other factors that affect the spread of the virus, such as population density, population movement, and virus mutation, etc., the public must know that the truth is that meteorological conditions are also important for the spread of the virus," Wen said.
And the researchers plan to work on creating "a mathematical model to predict daily or seasonal incidence rates by considering the highest temperature, minimum temperature, air pressure, humidity, radiation, population density, and population transmission," they wrote to close the paper.
"By improving our understanding of the impact of meteorological factors on the spread of COVID-19, a scientific control system can be established in order to reduce the risk of global virus transmission."
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
Report a Typo
News / Health
Ideal weather conditions may have helped coronavirus thrive initially, study suggests
By Mark Puleo, AccuWeather staff writer
Published May. 19, 2020 11:48 AM
A coronavirus lockdown has been imposed in a second city in China this week.
With the United States set for the unofficial beginning of summer over Memorial Day weekend, and the solstice following about a month later for the Northern Hemisphere, a recently published study from China may provide further insight into how weather, particularly summery conditions, may affect the spread of the new coronavirus.
The publication from researchers at Chengdu University of Information Technology in China analyzed the monthly average temperature, specific humidity and downward short-wave ultraviolet radiation in each Chinese province during the early days of the coronavirus outbreak.
The new study is the latest in a string of similar studies published in recent months that analyze how weather conditions might impact the spread of SARS-CoV-2, the pathogen that causes COVID-19.
The Chengdu researchers said the applications of the findings they came away with are incomplete, but the results suggest that numerous suitable weather factors may have laid an ideal foundation for the virus to take root and eventually spread throughout the world.
Using data from the European Center for Long-Term Weather Forecast (ECMWF), they compared the weather conditions with the number of confirmed cases from each province in China in January and February. According to the findings, there are three critical meteorological conditions in which SARS-CoV-2 can most effectively spread.
The first is temperature. The researchers said the analysis "showed that COVID-19 cases were concentrated in the provinces with temperatures in [the] range of 0–10 degrees Celsius," or 32 to 50 degrees Fahrenheit.
Workers wearing face masks and gloves serve lunch at a staff cafeteria in a semiconductor production facility for Renesas Electronics during a government-organized tour for journalists in Beijing, Thursday, May 14, 2020. (AP Photo/Mark Schiefelbein)
Increased humidity and UV light from the sun are the other two critical factors the researchers cited.
The researchers reported that the strength of solar radiation also may have an effect on how the virus spreads. Places where solar radiation remained below a certain level saw more effective spread, according to their findings. Meanwhile, higher-elevation locations, which see stronger amounts of UV rays due to their altitude, along with places that have drier climates, and therefore fewer clouds in the sky to diminish solar radiation, saw less transmission.
"The Qinghai-Tibet Plateau has a high altitude (approximately 4,000 m) and is subjected to strong solar radiation, resulting in a higher amount of UV-B radiation reaching the surface," the researchers wrote about a vast area covering 965,000 square miles of southwest China. The Qinghai-Tibet Plateau is about three miles above sea level and is nicknamed the "Roof of the World."
In the left (January) and right (February) columns, researchers tracked data for temperature (a and b), UV radiation (c and d) and humidity (e and f).
It's not just altitude that affects solar radiation. The number and thickness of clouds in the sky can also determine how much of the downward shortwave ultraviolet radiation -- energy emitted by the sun -- reaches the Earth's surface.
"The weather in the arid region of the Northwest is clear with fewer clouds, and the radiation received on the surface is higher than in other parts of China," the researchers wrote in the study. "As a result, it may be difficult for COVID-19 to spread in the plateau or the arid area in the northwest due to high UV-B radiation."
The study's results show a connection between areas that had lower numbers of cases that sit at higher altitudes and, therefore, received higher levels of UV-B radiation.
In an email to AccuWeather, Xiaohang Wen, the lead author of the study, said their findings don't only apply to China, but to the rest of the world as well.
In the study, the researchers said their findings will not just help the world understand how the virus first grew, but also how to prepare for dealing with it in the future.
"I think the virus is likely to start circulating in South America in July and August, and it will break out again in various countries in the northern hemisphere after October and November (If countries in the northern hemisphere do not adopt stricter prevention and control measures this autumn)," Wen said to AccuWeather.
Previous studies have also focused on those factors, particularly UV radiation. Data compiled by AccuWeather from the beginning of the year demonstrates the steady increase of UV rays in major cities as the calendar moves away from winter. Studies have suggested that a lack of UV radiation or vitamin D from sun exposure could be tied to stronger severity of COVID-19 cases in certain portions of the world.
Transmission electron micrograph of SARS-CoV-2 virus particles, isolated from a patient. Image captured and color-enhanced at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland.
(National Institute of Allergy and Infectious Diseases, NIH)
AccuWeather Meteorologist Michael Steinberg said there are numerous factors that go into determining how much UV radiation reaches the Earth and seasonality plays a crucial role.
"UV radiation is emitted by the sun in a near-constant amount, but the amount that reaches the Earth varies. It is partially blocked by the ozone layer and some kinds of clouds, especially thick ones, and influenced to a lesser degree by pressure, surface elevation, humidity, and several other factors," Steinberg said. "But the most important factors are the latitude, time of day, and time of year – these three determine the maximum possible level of UV – the actual amount is then determined by the other factors."
The Chengdu authors' findings, along with prior studies on the spread of seasonal influenza, show that even just a month of favorable environmental change can greatly reduce transmission.
“A further understanding of the environmental factors that are prevalent in the development of COVID-19 will help predict the potential risks of the global spread of this disease, and provide support for the prevention and surveillance of countries around the world,” they wrote.
A figure of a scatter plot from the published study shows how the number of confirmed cases in a province related to changing meteorological data in January, represented on the left, and February, represented on the right. (papers.ssrn.com)
To conduct their study, the researchers compiled data from January to February in each Chinese province to plot how changes in meteorological conditions correlated with the number of confirmed cases in each province.
In looking to the summer in the United States, Steinberg said humidity levels, temperature and UV radiation will be considerably higher than in the winter, when the outbreak erupted. These factors should greatly reduce transmission if the researchers' conclusions hold true.
"The amount of water vapor in the air (absolute humidity) and the specific humidity are typically much higher in the summer season, because the hotter air can hold more water vapor," Steinberg said. "When the relative humidity (which is what weather reports usually present) is 100% in the winter at a temperature of 30 F, there is only about half as much actual water vapor in the air as in the summer when the relative humidity is 25% but the temperature is 84 F."
In addition to a rise in humidity, the amount of solar radiation also increases significantly in the U.S. during summer, Steinberg explained.
"The seasonal variation is much greater at higher latitudes," he said, "but on average across the United States, the daily high UV Index level might be 8-9 in the summer and 2-3 in the winter."
The Chengdu team referenced prior studies that have shown that most enveloped viruses — such as coronaviruses — exhibit strong seasonality due to the hardening of the virus particle’s oily coating.
Warmer and more humid conditions are expected to soften that oily coating and make respiratory droplets fall to the ground more quickly, rather than lingering in the air.
A security worker, wearing a face mask, stands guard at the Disneyland theme park in Shanghai as it reopened Monday, May 11, 2020. With warmer weather and new coronavirus cases and deaths falling to near-zero, China has been reopening tourist sites such as the Great Wall and the Forbidden City palace complex in Beijing.(AP Photo/Sam McNeil)
Dr. Jeremy Rossman of Kent University previously told AccuWeather that he expects the summer months in the U.S. to help with slowing transmission due to the impact higher humidity levels have on respiratory droplets.
"As the country starts to have higher levels of humidity, we might see a small reduction in virus transmission," he said. "That might be really beneficial in terms of containment measures, but it shouldn't be enough that it would actually stop the virus on its own."
While the authors of the study added that many other factors, such as population flow, were not analyzed in this research, they argued that meteorological data points and weather patterns should be a focal point in future studies in order to better paint a full picture of COVID-19's scope.
"Although there are other factors that affect the spread of the virus, such as population density, population movement, and virus mutation, etc., the public must know that the truth is that meteorological conditions are also important for the spread of the virus," Wen said.
And the researchers plan to work on creating "a mathematical model to predict daily or seasonal incidence rates by considering the highest temperature, minimum temperature, air pressure, humidity, radiation, population density, and population transmission," they wrote to close the paper.
"By improving our understanding of the impact of meteorological factors on the spread of COVID-19, a scientific control system can be established in order to reduce the risk of global virus transmission."
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
Report a Typo