RPT: REVIEW - Spring Brings Hope For COVID-19 Decline But Scientists Not Rushing To Conclusions

BRUSSELS (Pakistan Point News / Sputnik - 01st April, 2020) Social media platforms are full of discussions about the potential impact of weather on the spread of coronavirus and it is often assumed that, similar to the regular "seasonal" influenza, good days for the Northern Hemisphere will be back together with warmth in April or May, but virologists do not generally rush to make certain conclusions, citing a current lack of data to render more or less accurate forecasts.

In its "Myth busters" information page, the World Health Organization (WHO), in turn, is very clear about the correlation between weather and the present epidemic, saying that the disease can be transmitted in all areas of the world irrespective of climate type and average temperatures.

"From the evidence so far, the COVID-19 virus can be transmitted in ALL AREAS, including areas with hot and humid weather. Regardless of climate, adopt protective measures if you live in, or travel to an area reporting COVID-19. The best way to protect yourself against COVID-19 is by frequently cleaning your hands. By doing this you eliminate viruses that may be on your hands and avoid infection that could occur by then touching your eyes, mouth, and nose," WHO says.

SUN AND HEAT LIMIT VIRUS LONGEVITY

Experts seem to agree on the fact that COVID-19 is less virulent and disappears faster on neutral surfaces in sunny and hot climates, although they often add that "adhering to good hygiene is more effective."

As the pandemic is hitting hard at New York and California, the North American press is full of panicky articles about coronavirus. However, amid all of it, Stefan Baral, an epidemiology expert at Johns Hopkins University, declares, comparing the COVID-19 pandemic to the seasonal flu, that he expects a "natural decrease in the coronavirus disease as the United States warms now that spring is there."

"There are three things that the coronavirus does not like: sunlight, heat and humidity. Sunlight will halve the ability of the virus to develop, so its half-life will be 2.5 minutes, and in the dark, it will be 13-20 minutes. Sunlight is really good at killing viruses ... Moreover, the COVID-19 is not very heat resistant, which means that the virus breaks down quickly when the temperature rises," John Nicholls, a clinical professor in pathology at the University of Hong Kong, says, as quoted by AccuWeather website.

Spring is in Europe and the United States. Temperatures in Rome have already risen to an average above 17 degrees Celsius (62.6 Fahrenheit). Temperatures above 20 Celsius are expected for the next weekend. In Spain, the Mediterranean coast is already warmer, while Madrid, which has been hit hard by the outbreak, is still struggling below 10 Celsius, but 17 is finally expected by the next weekend.

At the same time, in Tehran, temperatures have reached 17 degrees Celsius and will reach 19 next weekend.

However, Jean Ruelle, a researcher of the Institute of Experimental and Clinical Research at the Catholic University of Louvain (UCLouvain), told Sputnik that although the virus has restricted survival at high temperatures, it could not deactivate its transmission from person to person.

"Indeed, laboratory studies show that coronaviruses have decreased survival from heat and UV radiation. But this must be put in the context of transmissions. Contamination happens either by direct person-to-person transmission via droplets from an infected person, or indirectly by contaminated objects, which are then handled by the hands. If the survival of the virus in the environment is reduced under conditions of sunshine and heat, its inactivation is not immediate either. And this change in environmental conditions does not influence direct person-to-person transmissions," Ruelle said.

"The sun, light and heat are thus welcome, but it is hazardous to rely on the weather to resolve the current epidemic," the expert concluded.

As for the African continent, where the number of COVID-19 cases is rapidly rising but which has not still faced a dramatic outbreak like Europe, for example, Ruelle supposes that a greater spread of the virus to the region's countries is just a matter of time.

"Regarding Africa, I think, it is still too early to say anything, the pandemic has still not reached most parts of the continent. It is only a delay. There is also the issue of a number of tests carried out so far, which influences the data. Information is patchy and incomplete. To my knowledge, no scientific publications are allowing to support a hypothesis of better immune defenses in Africa for example compared to an ethnic origin or a particular microbial environment," the expert stated.

Even if the weather warms up in the Northern Hemisphere, the coronavirus can still survive for days at temperatures up to 25 degrees Celsius, according to a study carried out in Germany and published in the Journal of Hospital Infection. The study shows that the human coronavirus could persist for five days at a temperature of 21 degrees Celsius on a Teflon, ceramic or steel surface.

WILL SPRING BRING SIGNIFICANT IMPROVEMENT?

Sophie van Wambeke, a professor of epidemiology at the Earth and Climate Institute of UCLouvain, told Sputnik that it was currently too risky to draw certain parallels between seasons and the spread of coronavirus.

"Well, we observe in our regions that epidemics of respiratory diseases are rather associated with winter conditions, which can have different reasons. It is possible, indeed, that the warmth of spring reduces the progress of the virus in Western Europe, as it can be seen with other viruses, such as the flu. However, on the scale of the present pandemic, it should be emphasized that the Southern hemisphere, where the epidemic is also raging, is entering its winter season. Any parallel with observations on the seasonality of influenza, therefore, seems risky. We simply do not know yet," she explained.

The expert also noted that it was important to consider the transmission process and emergence of the virus separately when it comes to its dependence on climate conditions.

"If you envisage the climate in general and the influence it could have, the emergence and diffusion processes must be considered separately. The direct factors of the spread of the pandemic will be more immediate in the human-environment interaction and the interactions between human populations. Climate could act indirectly by modulating the degree and nature of these interactions, more directly when it is a pathogen involving other species. Mosquitoes, for example," van Wambeke said.

"However, let us note two elements which throw light on the question here: the emergence of this disease is not a phenomenon specific to tropical regions; and this emergence is a complex ecological process which involves a number of factors, among which human factors are very important, and among which the climate does not necessarily dominate. I do not think the climate can be considered as a direct factor in the epidemic of COVID-19," the scientist concluded.

The political world and citizens on social media insist on the fact that similar viral epidemics in the last few years somehow lost their virulence as the weather improved and days got warmer with the spring. This assumption has become a great hope for many.

"If the transmission is done in an aerosol way, with droplets as for the coronavirus which then gives respiratory symptoms, it is true that the virus remains a little longer active in a colder environment. But not all viruses are. Others are more easily transmitted at higher temperatures. If an epidemic becomes less virulent with good weather, it is mainly because people live less confined when the weather improves, and the aerosol spread is less efficient," Francois Dufrasne, a virologist at the Pole of Medical Microbiology at UCLouvain, told Sputnik.

Dufrasne added that global warming would definitely increase the risk of transmission of viruses from animals to humans.

"Global warming will, in the long term, increase the chances of virus transmission from animal reservoirs, and the last epidemics were all resulting form a transmission of a virus from animal to human. In the case of COVID-19, it seems that pangolins and bats were involved. But I am thinking more about the example of mosquito populations, which transmit viral diseases such as dengue or the West Nile disease. So, climate change has and will certainly influence the onset of pandemics, for example by expanding the range of insect vectors. The travel connections have become very simple and numerous in today's world; mosquitoes follow and adapt. It is not excluded that in 10-20 years, where it is still cold today, an increase in temperature, even of 2 degrees Celsius allows them to settle," he said.

IMMUNE SYSTEM MIGHT ALSO SUFFER

Despite the lack of studies indicating a link between immunity and ethnic origin or a particular microbial environment, some authors do link the virus' development and climate.

Climate change is likely to lead to future epidemics caused by viruses and other pathogens. It changes the way diseases spread and with pandemics like the coronavirus, we are learning in real-time how to deal with them.

For many scientists, higher temperatures can weaken or are weakening our natural immune system. The idea is that, when pathogens are exposed to gradually warmer temperatures in the natural world, they become better equipped to survive the high temperature inside the body, gradually reducing the efficiency of our body's defense mechanisms.

In the open access scientific publication of the American Society for Microbiology in MBio journal, Professor Arturo Casadevall from the Bloomberg school of Public Health of Johns Hopkins University demonstrated how a fungus called "Candida Auris," responsible for bloodstream-linked diseases, emerged simultaneously in three places, not linked to each other from 2013-2015. These three places and the vectors had nothing to do with each other Venezuela, Southeast Asia and South Africa.

The conclusion of Casadevall and his colleagues was that similar changing climate conditions lead to similar developments in different regions. It means that climate change can definitely be linked to new microbiological developments implying viruses, which, in turn, could trigger potential epidemics or even pandemics.

One thing is certain. The scientific community does not know much yet about COVID-19 but is learning fast. Vaccines are being developed all over the world, the most advanced works are being carried out in the US, where Johnson & Johnson is at the animal testing phase, and in China. Tests on humans will mean that the vaccines will only be available in the fall, at best, or early next year for the most pessimistic of experts.