High temperatures, air pressure, UV radiation can decrease the incidence of COVID-19

A new scientific article published on the prepress server medRxiv * shows that the spread of COVID-19, the respiratory disease that has spread worldwide to kill hundreds of thousands by 2020, shows that weather conditions reduce the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV- 2).

Novel SARS-CoV-2 coronavirus Transmission electron micrograph of a SARS-CoV-2 virus particle isolated from a patient. Image captured and enhanced in color at NIAID’s Integrated Research Center (IRF) in Fort Detrick, Maryland. Credit: NIAID

The threat

The spread of the new COVID-19 coronavirus disease in all countries and continents has been terrifying, with a total of 4.5 million infected cases and more than 300,000 deaths in just over four months.

COVID-19 usually begins with fever, dry cough, and shortness of breath develops later. The incubation period appears to be 5-6 days, on average, and not more than 14 days. Most fatal cases end with acute respiratory distress syndrome and multiple organ failure.

The rapid spread of the virus led the World Health Organization (WHO) to call it a pandemic.

Climate and viral spread

Some climatic conditions can cause a more significant interaction between the virus and humans, facilitating faster and greater contact and, therefore, a more extensive infection of the host.

Other meteorological variables can lead to increased human-to-human interactions and persistence of the virus on environmental surfaces, which can promote the spread of infection from one human to another.

Previous research on the correlation of weather conditions and the spread of the new coronavirus has been conflicting. In northern Europe, previous studies have shown that the spread of the influenza virus is easier in cold conditions and with a higher ultraviolet index.

A study from Jakarta, Indonesia showed that the only climatic variable that shows a significant correlation with the spread of the virus is the average temperature.

On the other hand, a recent Chinese study found that there was no link between heat or UV exposure and viral transmission.

Weather-COVID-19 Partnership Test in Japan

The current study focused on determining if this association was significant.

The study was conducted in Japan in all prefectures. The total number of confirmed cases of COVID-19 in each of them was collected in the period from January to April 2020. Similarly, the population density for each square kilometer of the habitable area was obtained by 2020. Finally, collected meteorological data for each. capital city of the prefectures during the same period.

Climate data included monthly air temperature in degrees Celsius, wind speed in m / s, air pressure at sea level in hPa, relative humidity in percent, percentage of possible sunlight, total monthly during the duration of sunlight in hours, the amount of rain in mm and the monthly average of the maximum daily UV index.

To arrive at a more significant rate of viral spread, the researchers calculated the total number of COVID-19 patients divided by the total population per 100 square kilometers of habitable area, which would compensate for the large differences in population density.

What did the findings show?

Analysis of the data showed that the incidence of COVID-19 varied with the meteorological data. The number of new cases decreased significantly with air temperature, air pressure, and ultraviolet radiation.

Caution: human behavior ahead

However, many other factors come into play, as explained by the eminent epidemiologist Marc Lipsitch of the Harvard T. H. Chan School of Public Health. List at least four modifiers among the environmental conditions that could influence viral spread:

1. Dry cold conditions favor the spread of the influenza virus because it is more stable and survives longer. This may not apply to SARS-CoV-2, which can make its way in very different climatic zones, from equatorial to arctic zones.

1. SARS-CoV-2 can survive up to 72 hours on plastic and stainless steel surfaces between 21-23 ^orC) and with 40% relative humidity. At 4 ^orC can survive for more than 28 days.

2. People spend more time indoors during winter and are closer to each other, favoring the spread of respiratory pathogens. In the case of COVID-19, it is not clear whether children, for example, contract the infection as easily or transmit it less or more than adults. This is an area where urgent research is needed.
3. Host immunity may decrease during winter, due to variations in the level of vitamin D, melatonin (a light-sensitive hormone that regulates the body’s circadian rhythms).
4. The number of susceptible hosts in the population at any time can interact with the above factors to cause seasonal variation, as well as cause seasonal epidemics. Since SARS-CoV-2 is a new virus, the low level of immunity in the population is a crucial advantage that hides any potential seasonality.

The researchers conclude that “higher air temperature, air pressure and UV rays may be associated with a lower incidence of Covid-19, which should be confirmed by additional epidemiological investigations that take into account other risk and protective factors. of the COVID-19 “.

However, scientists warn of the possibility of pinning our hopes on climate change rather than changes in human behavior to stop viral transmission. Environmental researcher Miguel Araujo from the National Museum of Natural Sciences in Madrid warns: “This is not an equation of one variable. The virus spreads from human to human. The more humans there are in a given place and the more they contact each other, the more infections there will be. Their behavior is key to understanding the spread of the virus. “

*Important news

medRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, guide clinical practice / health-related behavior, or be treated as established information