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Does SARS-CoV-2 dislike warm and humid weather?
A recent study shows that nine out of ten infections with the new SARS-CoV-2 coronavirus have so far occurred in regions in which the average daytime temperature was between three degrees Celsius and 17 degrees Celsius. In addition, the absolute humidity in the regions was four to nine grams per cubic meter. The American research team predicts that summer can weaken the pandemic.
Researchers at the Massachusetts Institute of Technology examined the pattern of distribution of the new SARS-CoV-2 coronavirus, noting that the virus was particularly prevalent in countries where weather conditions were similar to those in China at the time of the outbreak. In contrast, China-related countries with a warmer and humid climate such as Singapore, Malaysia, Thailand and other Southeast Asian countries have significantly lower growth rates. The results were recently published in the journal "Social Science Research Network".
Similar weather conditions
The research team found that the number of cases increased most in countries with similar weather conditions to those in the heavily affected region of Hubei in China. According to the study team, similar weather conditions prevailed in Italy, Iran and South Korea at the time of the rapid spread as in Wuhan and other Chinese cities, in which the corona virus spread widely.
SARS-CoV-2 seems to avoid warm regions
The virus seems to prefer a daily average temperature between 3 ° C and 10 ° C with a humidity of 4 to 9 g / m3. This thesis is also supported by the fact that the virus spread less strongly in warmer regions such as Thailand, which are in close proximity to China. In addition, the researchers showed that there is also a striking north-south divide in the spread within the United States. In the cooler states of the north, more illnesses are reported than in the warmer states of the south. Even in California, the number of cases in the north is twice that in the south.
However, there are also two states that do not fit this picture. These include the state of Oregon, which registered few diseases despite its relatively northern location, and the state of Louisiana, in which a relatively large number of diseases were reported despite its southern location.
SARS-CoV-2 seems to prefer dry air
In addition, the team led by research leader Qasim Bukhari found that by March 11, 2020, 90 percent of all infections had occurred in places where the absolute humidity was between 4 and 9 g / m3. In any case, high humidity is an obstacle to the spread of respiratory diseases.
Similar observations from China
Chinese observers from Tsinghua University also reported similar observations. They reported that in 100 Chinese cities, the rate of new infections decreased as the temperature and humidity increased.
The Chinese researchers calculated that the so-called basic reproduction number drops due to rising temperature and humidity. This number indicates how many more people infect a sick person. If this value is 1, a sick person infects another person. To stop an epidemic, this value would have to drop below 1. The Robert Koch Institute estimates the basic reproduction number of Covid-19 at 2.4 to 3.3. The Chinese research team calculated that for every degree of temperature rise, the base reproductive number decreased by 0.0383. The number also fell by a further 0.0224 per 1 percent increase in relative humidity.
The actual impact will be shown shortly
It will be seen in the coming months whether the two research teams are right. However, the researchers emphasize that the results do not suggest that SARS-CoV-2 cannot spread in warm areas. The calculations are based on the data currently available and there are many unknown factors. Many virologists, such as Christian Drosten, also emphasize that an increase in temperature may be beneficial for containment, but that this alone is unlikely to be enough to stop the epidemic. (vb)
Read also: COVID-19 Diseases: Rate Decreased Nationwide in the past week.
Author and source information
This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
Graduate editor (FH) Volker Blasek
- Qasim Bukhari, including: Will Coronavirus Pandemic Diminish by Summer? in: Social Science Research Network, 2020, papers.ssrn.com
- RKI: SARS-CoV-2 Fact Sheet for Coronavirus Disease-2019 (COVID-19) (as of March 23, 2020), rki.de
- Jingyuan Wang, Ke Tang, Kai Feng, et al .: High Temperature and High Humidity Reduce the Transmission of COVID-19; Tsinghua University, 2020, arxiv.org