Corona pandemic: will spring and summer help? Virologist Christian Drosten is skeptical


Researchers see a connection between the coronavirus and weather influences. Virologists, however, warn against hoping too high for spring.

  • Experts believe that factors such as Humidity or UV light consequences on Corona could have.
  • Virology Christian Drosten warns against drawing too fast conclusions from the Weather on the infection process.
  • Corona-News: You can find all the news on our topic page.

Frankfurt – When the warmer temperatures in spring If many people move outdoors and they no longer spend as much time together in closed rooms, the risk of infection with the decreases Coronavirus. It is not for nothing that the whole of Germany has discovered walking as a new “hobby”.

And also the general risk of colds as well Flu viruses reduce in spring. But spring also has an effect on that Coronavirus self? Researchers disagree, but point to certain environmental influences on the Covid-19Pathogen and its spread.

Corona in spring: No specific factors for virus seasonality

In fact, the number of infections in Germany subsided in the summer of 2020. The Robert Koch Institute (RKI) assumes that Sars-CoV-2 more common in the colder months of the year than in summer.

Corona: The virologist Christian Drosten is dampening hopes for a relaxed summer.

© Jürgen Heinrich via

According to Ulf Dittmer, director of the Institute for Virology at the Essen University Hospital, the course of the pandemic will be determined by a variety of factors. A clear forecast is therefore difficult. “The seasonality of Virusesthat are spread via the respiratory tract is extremely complex and cannot be determined by individual factors, ”says Dittmer.

Various environmental influences affect the virus – changed properties of the droplets

The virologist Stephanie Pfänder from the Ruhr University Bochum sees certain environmental influences as having an effect on this Virus. According to Pfänder, environmental factors can, for example, affect the persistence and resistance of the virus. The environmental conditions would also have an impact on the properties of aerosols or droplets with which the virus is spread.

Among the decisive environmental influences, she counts factors such as temperature, Humidity and UV radiation. For this, basic knowledge could be derived through studies.

Behavior as an important factor influencing the risk of coronavirus transmission

In addition to weather-related factors, other aspects determine the course of the pandemic, such as people’s behavior, according to virologist Ulf Dittmer.

In winter we tend to stay in closed rooms, in the spring and summer Many are more drawn to the outdoors. “If all of life happens outside in the fresh air or rooms are consistently well ventilated, that is it Transmission risk naturally lower, ”says the virologist Pfänder.

Spring during Corona: The risk of infection for the virus is lower outdoors. (Symbol image)

© Caroline Seidel

Corona in spring: effects of temperature and humidity

According to the virologist Ulf Dittmer, the virus envelope is particularly stable outdoors at a temperature of around ten degrees: “The warmer it gets, the more the stability decreases.” The heat changes fat molecules in the envelope in such a way that they can burst.

According to the Leipzig aerosol researcher Ajit Ahlawat, air humidity plays an important role, especially indoors. For this purpose, investigations into transmissions of the Coronavirus carried out in closed rooms. Together with other researchers, the scientist from the Leibniz Institute for Tropospheric Research (Tropos) found out that the risk of infection inside is lower at higher humidity.

Seasonal effects on corona: UV light is more important than humidity and temperature

“If the relative humidity of the room air is below 40 percent, the virus particles emitted by the infected absorb less water. So they don’t sink to the ground as quickly, but stay in the air and are more likely to be inhaled by healthy people, ”explains Ahlawat.

The condition of the nasal mucous membranes is also at risk for Virus-Transfers to be considered. In dry air these become drier and therefore more permeable to Viruses. However, a lower risk of infection from less dry nasal mucous membranes outdoors cannot be derived directly from these findings, according to Ahlawat. Outside there would be other factors, mainly the dilution of the aerosol particles in the air and that they are in the UV light be less active. These factors played a bigger role than outdoors temperature and Humidity.

UV radiation and vitamin D: protection against corona infection in spring is not certain

Sun rays – in particular UV radiation – damage the genetic information of the Virus. “You can roughly say that UV radiation is able to inactivate the virus by attacking the viral nucleic acid,” says the virologist Pfänder. The viruses are then no longer infectious.

According to the German Nutrition Society (DGE), vitamin D formed with the help of sunlight has regulatory effects on it immune system. However, I am still not sure if it is before one Corona infection can protect. According to the RKI, the Vitamin-DDue to the geographical location in Central Europe, formation is only possible in the summer half-year (March to October). In winter, the body uses the vitamin D reserves built up in summer.

Innate and learned mechanisms of the immune system – more efficient defense against new viruses in summer

The human defense system has to protect us from various attacks: bacteria, fungi – or even Viruses. For every intruder, the body tries to use a suitable reaction, also known as an immune response: “Having everything ready at the same time, but would cost a lot of energy,” explains the Giessen immunologist Eva Peters. That’s why it fits immune system his reactions to the season. There are two different types of immune response for this: the innate and the learned.

In winter, a learned immune response is usually required for problems that have arisen in the past. Such as Cold virusesfor which the body had previously antibody formed. This learned specific immune response is very precise, but only builds up slowly.

Im spring and summer on the other hand, if people spend more time outdoors, the body is also exposed to unknown risks. Here the immune system uses the innate, unspecific immune response. This could be used to quickly identify intruders such as viruses based on certain damage patterns. “That means that in summer our immune system is better at fighting off new germs quickly and efficiently. That also applies Sars-CoV-2 too, ”says Peters.

Christian Drosten: Warm temperatures are not decisive for reducing the corona numbers

But Christian Drosten, Head of Virology at the Berlin Charité, warns against drawing too fast conclusions about the time of year. True, they are Infection numbers decreased in Germany in summer 2020, but after one in Spain Lockdown increased again despite the heat.

Drosten believes that it is unlikely that the transmission dynamics of the past year can also be used to draw conclusions about the summer of 2021: “The fact that we had such a relaxed summer in 2020 was probably due to the fact that our case numbers remained below a critical threshold in spring. But that is no longer the case, ”he told the“ Spiegel ”.

Christian Drosten, virologist at Charité Berlin, at the federal press conference. (Archive photo)

© Reiner Zensen / Imago Images

Weather influences exist in spring – but the effects on pandemic events are uncertain

temperature, UV radiation, Vitamin D: “All of these factors improve in the spring and in summer“, Summarizes virologist Dittmer. So there are seasonal effects. But how much the weather influences the pandemic is still lacking concrete information.

“We know of Coronavirenthat the R-value, i.e. the reproduction rate of the Virus, due to these factors drops significantly in spring and summer. So at least by a factor of 0.5, maybe even more. And that’s quite a lot, ”explains Dittmer. However, the past year also showed that the seasonal effects did not lead to a complete disappearance.

Influence of spring weather: Corona mutants as an unknown factor

Now, according to the experts, there is another unknown danger: the The virus mutation. The benefit gained by the seasonal effects could be from the more infectious Mutants are virtually “eaten up”, says virologist Dittmer. This could show itself in the coming months despite the warmer weather. The seasonal effects could then possibly not be sufficient for the R-value to fall below the threshold of 1 above which the Corona-Pandemie subsides.

Virologist Pfänder assumes that the warmer season can in principle already contribute to slowing down the transmission dynamics. She also sees uncertainty among them Mutants. “The occurrence and spread of mutants is actually a factor that is unpredictable.” (Anna Charlotte Groos with dpa)

List of rubric lists: © Jürgen Heinrich via

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Corona pandemic spring summer Virologist Christian Drosten skeptical


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