D.Numerous scientific studies have shown that most infections and infectious diseases are actually characterized by seasonal movements – we are talking about “seasonal”: warmer seasons are more conducive to the disappearance or reduction of infections born during the cold season.
For example, this is the so-called “seasonal” flu. Jeffrey Shaman and Melvin Cohn, for researchers Fever intensifies during the winter, When the temperature and humidity are very low. Thus, the Covid-19 virus is no different, with evidence of its dynamics in the seasons and hemispheres over the past three waves.
But what about the scientific studies on Govit-19 in particular? Can we really trust a stimulus from the summer along with the vaccine to bring down the masks?
Effect of moisture and solar radiation
This has been shown by many laboratory studies including Thug Camp and his colleagues Released in 2020 – Resistance to SARS-CoV-2 Owned Human Corona Viruses, Through Drops and Air Surfaces, Is significantly reduced by hot and humid conditions.
Resistance of human corona viruses to airborne droplets and surfaces is significantly reduced by hot and humid conditions
Conversely, under dry conditions, water in droplets quickly evaporates causing the virus to stagnate in the air, increasing its spread, especially in poorly ventilated and controlled environments.
The results of studies on other human corona viruses point in one direction Reduced stability in warmer climates. In 2011, researcher K.H. Chan and his colleagues confirmed that the reliability of the virus for SARS-CoV-2 was rapidly deteriorating. At high temperature and humidity levels.
Cold, dry conditions – especially in environments that use air conditioning and / or polluted conditions – Increasing the spread of the virus.
From laboratories to statistical analysis
Are the results of laboratory studies statistically valid? To the researcher Florence Dushabe, It will be like that: “In terms of infection and mortality, the severity of the disease is 6 times higher in countries located in the temperate region. Infections in tropical countries account for only 4% of worldwide epidemics with low mortality (2.5%). ”
To Simiao Sen and his team, their works have been published Scientific reports, Will work in support of reducing the number of Govt cases to one million people near the equator. According to other studies, as mentioned, there are weather conditions in which the virus is particularly contagious in moderation. Italy, The onset of the epidemic in the winter of 2020.
However, to be precise, the industrialized countries of the Northern Hemisphere (Europe and the United States) have weather conditions, so temperatures are average within this range, and the weather effects of the virus are weak.
It may have contributed to the development of the epidemic within these countries, especially during the first wave and, especially in cities Air quality was reduced, As in the Lombardy and Madrid region.
The relationship between climatic factors and Govt-19 may be more complex. Temperature conditions may have “linear” statistical relationships Intense violets In particular: a very negative or very positive temperature shortens the survival of the virus, but a moderate temperature does not cause a moderate or impact.
Jorge Luo and his colleagues More skepticism Regarding the significant relationship between humidity and virus survival rates in China.
Other studies are moving in the same direction: For example Spain, Alvaro Pris-Radon and Angel Serrano-Aroca do not see a significant effect of temperature, controlling – here “by combining variables” to understand – population density or number of passengers may be dependent on previous study results.
Beyond the role of temperature and humidity, the most recent studies have found the role of ultraviolet rays, solar radiation and wind speed.
“Outbreaks appear to be exacerbated 6 times higher in countries with a moderate incidence of morbidity and mortality”
Florence Tushabe, researcher
In the review January 2021 PNAS, For a group of 173 countries, as Dhamma Carleton and colleagues have shown, high daily UV light reduces the overall growth rate of Covit-19 cases by up to two and a half weeks; On the other hand, they do not have a significant effect on temperature and humidity levels.
In conclusion, the correlation between climatic conditions and Govt-19 will be significant, but to a lesser extent Expert Rachel Baker has already written In review Science From the summer of 2020.
Although high temperatures and strong UV levels in the summer may help reduce the virus’s circulation, it may not be sufficient to reduce its circulation in the population without the need to maintain sensitivity to SARS-CoV-2 to weather conditions. Social distance policies.
Therefore, the climate will play a positive but moderate role in the fight against Govt-19, which was recently highlighted. Dhamma Carleton and his colleagues.
An impact that is somewhat present
This is what we show An article has now appeared in the press BLOSE One, And about a sample of 37 industrialized OECD countries observed during the first wave of the Govt-19 epidemic.
Rising temperatures, solar radiation and humidity have significantly reduced the number of cases and deaths since Kovit-19, but to some extent our results suggest.
The effects were primarily measured at 7 days in the number of cases, which is similar to the minimum incubation period, but takes into account up to 28 days of integration and hospitalization periods.
In a related work – not yet reviewed – these results are confirmed by the rates for hospitalization in France, based on data collected in about fifteen major cities for the first wave.
The climate may explain, albeit slightly, why the north and east of France were most affected during the first wave of the epidemic.
We also show that air quality is an important additional determinant of the virus, as pollution exacerbates its impact on French cities under our study.
Question about movement
In our study published in BLOSE OneLet us recall that in the model of the OECD countries, we went further than the existing literature, taking into account the way weather conditions may affect the spread of COV-19 according to individual movement conditions.
We wondered if our movements (like car, walking, etc.) were affected by weather conditions, and if so, how this could affect the spread of the virus.
Based on data covering the period from January to September 2020, the movement is increasing the spread of the virus: more people are moving, moving in groups, going out, communicating, and the rate of transmission is likely to increase, which is not surprising.
However, after three weeks in our sample the effects were not known. This means that it is necessary to take into account the incubation and stabilization periods of the virus to experience the effects of the weather on the cov. However, the very short-term relationship is not clear.
However, favorable weather (sunlight, temperature) increases our desire to go outside (terraces, friends, supermarkets, parks, etc.), which mechanically increases the circulation of the virus.
Double effect of temperature
After all, the beneficial effect of weather conditions on the Govit-19, due to its interaction with the movement of individuals, is somewhat mitigated by this increased mobility: a beautiful hot and sunny day certainly allows for better ventilation of its interior, thus reducing the stability of the virus, but it is also the terrace of a hotel. Or even in a park, it encourages people to go out more and interact more with others by increasing the number of contacts, which further reduces social distance.
All this will lead to an increase in the circulation of the virus and the number of cases. This mechanism becomes even clearer if some or all social interactions take place indoors, in confined and poorly ventilated areas – and if air conditioning such as summer helps to increase the spread of the virus.
We have shown that individual movement increases the circulation of the virus when weather conditions are favorable, thus minimizing the beneficial effect of the latter on this cycle.
Keep in mind that the absence of social exclusion and the wearing of the mask was marked as high last year, so the indirect effects we have identified should be dramatically lower in 2021.
Nevertheless, it is advisable to be cautious in dealing with the indirect consequences of which health conditions may deteriorate too quickly, and with favorable weather conditions for an increase in social interactions.