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Will warmer spring weather slow down the #COVID19 virus spread? And can colder weather make it worse? What do we know so far and what to expect

As the new Coronavirus disease COVID-19 outbreak continues to distribute with an accelerating rate, many are asking how this can be stopped. Could the coming warmer spring weather slow down the virus distribution, similar to the flu season characteristics? Could potential cold outbreaks (which are foreseen in the coming weeks across both continents) make it even worse? It has now been officially announced that COVID-19 is characterized as a pandemic. As of March 12th, more than 130.000 infections and nearly 5.000 deaths were reported globally. The worst numbers are in Italy and Iran.

We have been requested to help with the public awareness on this global topic lately. Let us see what we know so far and what we don’t know. Yet.


NEW UPDATE: The #COVID-19 environmental factual effect over Italy: The nationwide lockdown leads to significant decline in nitrogen dioxide (NO2) emission

The #COVID-19 environmental factual effect over Italy: The nationwide lockdown leads to significant decline in nitrogen dioxide (NO2) emission


The global distribution so far:

Global distribution. Image by Center for Systems Science and Engineering at the John Hopkins University

Could the climate be a factor for its spread?

Well, it is too early to know exactly. Experts say sunlight and heat limit the growth and longevity of the virus. As the COVID-19 has begun in late 2019 in China, its distribution period over only 3-4 months is very short. However, some signals have been found on how the disease responds to the variable climate over the continents. The latest report by WHO (World Health Organization) suggests there is further deeper research needed to investigate the stronger correlation between Covid-19 and higher temperatures. There are some discussions about how higher temperatures, high humidity, and sunlight ould limit the virus spread:

Sunlight will cut the virus’s ability to grow in half, so the half-life will be 2.5 minutes, and in the dark, it’s about 13 to 20 [minutes]. Sunlight is really good at killing viruses,” Dr. John Nicholls, a pathology professor at the University of Hong Kong, said.

Deutsche Welle also cited Thomas Pietschmann, a virologist from Germany’s Centre for Experimental and Clinical Infection Research, who said the coronavirus is “not very heat-resistant, which means that the virus quickly breaks down when temperatures rise”.

See the official WHO full report here: WHO report, March 5th, 2020.

Distribution across the European continent (as of March 12th, 2020):

Is there actually any evidence of Covid-19 (or Coronavirus) correlation with weather climate?

Some research analysis did show some similarities over the areas where the virus spread has been the most intense through the population so far. Researches made a comparison of virus distribution over the mid-latitudes in China (Wuhan), north Italy (Milan) and Northwest US (Seattle). These areas share a similar climate during winter months, with temperatures ranging between 5-11 °C (41-52 degrees F) and humidity 47-79 %. Researchers found that in hotter and more humid air regions (e.g. closer to tropical regions), the virus has been limited to the people that brought it from outside, while there are basically very low signals of its secondary distribution. In other words – there is a strong signal the spread inside the region is minimal. However, this still has to be taken with extreme caution due to a very low number of cases over that region, and these assumptions might not be accurate yet.

To date, Coronavirus Disease 2019 (COVID-19), caused by SARS-CoV-2, has established significant community spread in cities and regions only along with a narrow east-west distribution roughly along the 30-50 N” corridor at consistently similar weather patterns (5-11 degrees Celsius and 47-79% humidity).

Temperature and Latitude Analysis to Predict Potential Spread and Seasonality for COVID-19

Can we compare the season behaviour of flu and Covid-19?

The first investigations on COVID-19 introduce similarities with some other studies how influenza (known as “flu”) spreads. The study has found that high temperatures and especially higher humidity significantly slows down the virus spread. With very high humidity, it even stops the spread.

The warmer air can hold more moisture, which prevents airborne viruses from traveling less than they would in dry air. In humid conditions, the small liquid droplets in a cough or sneeze gather more moisture as they’re expelled. Eventually too heavy to stay airborne, they drop to the ground.

Taking these facts into the account, we see the flu spreads more during cold and dry months, and vanishes during hotter and more humid months. However, studies have shown the tropical region has more cases during rainy months, probably as people stay indoors. First comparisons do show the COVID-19 has much higher fatality rate:

COVID-19 vs. season flu fatality rates:

Harvard epidemiologist Marc Lipsitch doesn’t think any weather changes will put a big dent in how the virus spreads. COVID-19 has now been documented around the world. If the virus is anything like a typical flu virus, it may worsen in Southern Hemisphere regions as the seasons change.

Distribution across the United States (as of March 12th, 2020):

The Cumulative number of cases, by a number of days since 100th case across the most affected countries; we can see how robust the spread is over United States, Italy, Iran and also Spain:

So, can we make some conclusions for this spring?

What can we expect with the upcoming warmer weather this spring or with a potential cold outbreak that may happen until May? While health experts mostly agree the warmer weather could be the key factor with the virus distribution, the final outcome undoubtedly strongly depends on each country’s response and how robust its healthcare infrastructure is made and also how pro-active the citizens are. Relying only on the warmer weather patterns without taking into account the safety precautions and other health protocols brings a high risk for the final outcome. Even as the weather warms up in the northern hemisphere, the COVID-19 may still survive for days (or weeks) at temperatures up to 25 °C (= 77 F), according to a study in Germany published by the Journal of Hospital Infection.

Based on the latest global model guidance for North American and European continents, we can see they can both expect some colder weather patterns return in the coming weeks, possibly even with intense cold outbreaks. Attached are March 12th Ensemble model forecasts for both continents:

Final words:

We are investigating and monitoring the weather patterns across Europe and the United States, so we can see how the virus spread correlates with the currently known facts. More updates will follow in this article and also additional details in the future. Stay tuned and please stay safe!

Check out these useful links about the COVID-19 disease, how to protect yourself, find the latest reports and research papers:

The symptoms of coronavirus disease COVID-19: