Climate Change

Summer commences in India, impact on COVID-19 unclear as of now

More data expected in next 2 weeks, especially on the virus, humidity and ultra-violet radiation

By Akshit Sangomla
Published: Monday 13 April 2020
Novel coronavirus and weather

There has been speculation about the connection between COVID-19 and higher temperatures. The summer season has started in India as temperatures have started rising in the second week of April, 2020, after a rainy and cool month of March.

The temperatures though are not as high as expected. “The extended range forecast from India Meteorological Department (IMD) already indicated that April was going to be cooler than normal and that has happened thus far,” Raghu Murtugudde, climate scientist at the University of Maryland in the United States, said.

There might be a link between the unusual weather in March and early April and the decrease in air pollution and aerosol dispersal in China due to lockdowns implemented to control the spread of the COVID-19 pandemic, Murtugudde said.

“Pre-monsoon showers are not out of the question in a natural world but the biggest signal we have is the dramatic drop in greenhouse gases and aerosols / pollution,” Murtugudde pointed out.

“China got clean before us and this would have impacted the elevated heating over Tibet as well as the Eurasian snow cover. Reduced aerosols also have an impact on land warming and ocean warming,” he said.

“How these are all modulating the monsoon circulation and the pre-monsoon shower activity is not totally clear right now from observations. Some modelling studies are being performed, which will shed some light soon enough,” he added.

Maximum temperatures crossed the 40 degrees Celsius mark in parts of Gujarat, Maharashtra, Rajasthan and Madhya Pradesh on April 11. These values were 1-4°C above normal, according to data from IMD.

The rest of India has much lower maximum temperatures. In fact, large parts of eastern, central and southern parts of the country still have maximum temperatures 1-3°C below normal.

The IMD earlier predicted a warmer than usual summer season this year. Average maximum temperatures are likely to be warmer than usual by 0.5-1°C for April-May-June according to the latest seasonal outlook for temperatures released by IMD.

These temperatures will be warmer-than-usual over east and west Rajasthan, west Madhya Pradesh, Gujarat, Konkan and Goa, Madhya Maharashtra, Marathwada, north and south interior Karnataka, coastal Karnataka, Rayalaseema and Kerala.

Weather and COVID-19

There is a link between weather factors such as temperature and humidity on the spread of the CoVID-19 pandemic according to experts but they are still unsure about the exact impact.

There are two ways that scientists explore the relationship between weather and the spread of diseases, according to a rapid expert consultation published by the US National Academies Press on April 7, 2020.

This assessment was conducted by the members of the National Academies’ Standing Committee on Emerging Infectious Diseases and 21st century Health Threats.

The first way is through laboratory experiment studies conducted by spreading an artificially grown version of the SARS-CoV-2 virus that causes CoVID-19 disease, within controlled environmental conditions and observing its behaviour.

The second way is through natural history studies which take into account the spread of the disease in actual environmental conditions in different places throughout the year. Both these methods have their shortfalls.

While for experimental studies, the controlled environmental conditions are never close enough to the real-life conditions, for natural histories there are too many factors involved to pin point the exact causes of the spread of the disease.

It is also difficult to bring the results of these two ways to come to a conclusion as they are so different from each other. 

Laboratory data available so far indicated reduced survival of the virus at elevated temperatures, the paper stated. For instance, a research paper from Hong Kong said there was around 50 per cent reduction in the concentration of the virus in seven days at 22°C while there was no detection of virus after 14 days.

At 37°C, the time period of 50 per cent reduction was reduced to just one day and no virus was detected after that, showing that an increase in temperature does have an effect on the survival of the virus.

The relationship of the virus with temperature changes with the surface it is present on, with time, the paper said. The virus can survive on printing and tissue paper for three hours, on cloth for two days and on stainless steel for seven days.

One alarming result was that there was some virus left on personnel protection equipment masks even on the seventh day after it was introduced, perhaps hinting at the reason why many medical professionals at the forefront of CoVID-19 treatment and control are getting infected by the disease.

Another study being conducted at the Tulane University National Primate Research Centre in Louisiana suggests that the SARS-CoV-2 virus might have a longer half-life than the influenza virus, SARS-CoV-1 virus, monkeypox virus and tuberculosis bacteria at 23°C and 50 per cent relative humidity.

The scientists caution that the number of well-controlled studies is small in number right now and the survival properties of the real-world virus might be different to the artificially grown studies being used in these studies.

Most of the laboratories are also unable to control humidity levels efficiently, leading to improper testing conditions. Moreover, the testing conditions in all these experiments are different from one another which means that no correlations or conclusions can be drawn from them.

More data is expected in the current week and next, especially related to the relationship between the virus and humidity and ultra-violet radiation.

On the other hand, natural history studies remain even more inconclusive regarding the seasonality of CoVID-19 because of poor data quality and a paucity of time since the beginning of the pandemic to draw effective conclusions.

Even though some studies do suggest that the spread of the disease might slow down in higher ambient temperatures and humidities, the slowing down might not be significant as the human population lacks immunity to the virus as of now.

“There are some papers claiming that there is a relation between temperature and humidity and COVID infections and mortalities. But this signal may be true in a natural system and we have moved the virus by human travel and may be also by shipments into regions,” Murtugudde said.

So it is hard to separate the environmental impacts right now.

“One clue is that the midlatitude countries tend to have a strong seasonality in flu and to the extent that CoVID-19 is a flu-like disease, it may end up becoming seasonal,” Murtugudde said.

Tropics do not have seasonal flu. Rather, it can occur anytime. “Like all life forms, coronavirus will also have a range of tolerance for surviving in the open environment but what is most important now is to see what it does once it finds a host after being transported by travel and shipments,” Murtugudde concluded. 

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