How The Spread Of The New Coronavirus May Fluctuate With Temperature?

Fluctuation In COVID-19 Spread According To Different Temperatures

In our previous blog on the outbreak of COVID-19, we looked at how the overestimation of nations resulted in serious consequences. The number of corona positive cases and deaths around the world are still on the rise. And until date, scientists have been trying hard to discover a vaccine or an antiviral drug to fight the virus.

Hence, countries starting to be hit by the outbreak are finding ‘lockdown’ as the best preventive measure. Keeping a social distance will stop the virus from human to human transmission. Some are seeing this as a broader solution to stop the transmission chain. Whereas others believe it as buying time to find a solution to this pandemic.

Amidst all this disruption to normal life, scientists are studying the nature of this new coronavirus. Dozens of researches are revealing the potency of COVID-19 in different climates. In our third chapter exploring the epidemic, we attempt to find out if there is really any truth: Does extreme temperature retard the spread of COVID-19?

How High Temperatures May Demotivate The New Coronavirus?

How Climate Change Can Affect Coronavirus?

According to a study, a warm and humid climate is linked to the slower speed of COVID-19. This study was conducted by Qasim Bukhari and a team of scientists from the Massachusetts Institute of Technology (MIT). They assessed the data on the number of infections worldwide by comparing it with two global climate parameters – temperature and humidity. The study suggests that Asian countries experiencing monsoon may have lower chances of the transmission. 

The findings show that 90% of the virus transmissions until March 22, 2020, happened in regions with a temperature between 3-7℃. Moreover, the absolute density of these regions during this time was between 4 to 9 g/m3. 

The MIT scientists also marked that the total number of cases in nations with temperature higher than 18℃ was less than 6%. And the humidity was greater than 4 to 9 g/m3 between January and early March. 


Temperature Impact In China 

Now we delve into another study specific to China. The findings analysed data from Wuhan, the Chinese epicentre of the coronavirus outbreak. Shockingly, it unveiled that the virus seems to be spreading at a faster rate in summer climate. In particular, the optimum temperature they found to be 19℃ and humidity 75% with less than 30 mm of rain in a month.

To a big concern, the researcher also found that cold air destroys the virus. As per their study, containment measures should be built up as the temperature rises. 

However, more alarmingly, the next 11 similar studies concluded the opposite of this study. One such research looked at all 80,981 cases in the central region of China between January 20, 2020 to February 29, 2020. It showed that the optimum temperature for virus spread is 10℃. Further, it said that temperatures lower or higher retard its transmission capacity. With that, it didn’t find any link with humidity.

Study On The Spread In The US

A study focusing on the transmission capacity of COVID-19 in the US shows a different situation in the north and south. The northern states of the country have seen much higher growth rate as opposed to southern states. The point to note here is that the weather in northern states is cooler while in the south it is warmer. In addition, the study marked that cases have been limited in Arizona, New Mexico and Texas – located towards the south.

On the other side, the northern region of California has double the number of cases compared to its south. Intriguingly, Oregon and Louisiana are not in this chain despite situated in between California and Washington – hotspots of the virus. Oregon reportedly has nearly 200 cases and Louisiana has over 1000 by March 22, 2020. If we take the case of Oregon and Louisiana, the latter has more cases despite having a warmer climate. 

Why Coronavirus May Spread More In The Winter Season?

Several infectious diseases tend to have a seasonal pattern in their incidence. Take, for example, an influenza virus that shows a significant difference in its potential to spread in different seasons. Mostly flu surges in dry temperate regions while it displays less incidence in tropical areas. Scientifically, there are three reasons for this. 

  • Viruses are more stable in cold and dry conditions with low levels of ultraviolet light. 
  • In winter, people spend more time indoors which increases the chances of human to human transmission. 
  • The vitamin D deficiency during the winter when the Sun is mild weakens our immune system. This gives the virus the windows to attack our immunity.

The novel coronavirus causes common cold symptoms that are similar to the flu or pneumonia. Hence, considering this factor, this newfound virus is likely to be more aggressive during the winter – or in temperate regions of the world.

What Do Indian Microbiologists Have To Say?

Microbiologists Study on COVID-19

Currently, India is on a 21-day lockdown on account of tackling the COVID-19 crisis. There is a big hope that towards the end of April, the country will have the leverage to prevent the pandemic. Because during this time, most parts in the country experience extreme summer. This report as per Professor J.S Virdi, an eminent microbiologist and Chief of the Association of Microbiologists in India (AMI).

According to virologists, the new coronavirus is more active between December and April. The same pattern has been detected in the spread of Influenza as well. Similarly, other viruses such as SARS or Flu show the maximum spread between from October to March. This clarifies that temperature definitely has a role in creating a certain pattern during the virus outbreak. Thus, by the end of June, the impact of the virus will be less compared to the present statistics.

Professor Pratyoosh Shukla, General Secretary of AMI, Chinese collaborators have informed that COVID-19 resistance power cannot tolerate high temperature. All put together, the outbreak suggests preference over cool and dry regions.

Furthermore, Professor Virdi says that in my fifty years of career as a microbiologist, he has “never seen a virus spreading at such an electrifying speed. And the fact that it is spreading at such a speed suggests that it is airborne.”

Temperatures Across The World During COVID-19 Spread

Here is a list of countries severely hit by COVID-19. Follow the list and make your own analysis and compare it with the studies mentioned here.

CountryAverage Temperature Range COVID-19 Cases 
ChinaJan-Feb 2020 (7-13℃)78,824
Italy Feb-Mar 2020 (4-9℃)101,739
Spain Feb-Mar 2020 (5-17℃)95,923
Germany Feb-Mar 2020 (1-9℃)71,808
IranFeb-Mar 2020 (3-17℃)29,084
FranceFeb-Mar 2020 (3-8℃)52,128
USAMar-Apr 2020 (6-16℃)215,003

The list given above shows that each country first hit by the outbreak has lower temperatures than those in warmer areas. That said, it is yet not clear that only colder regions have a greater threat of the spread. Researchers emphasise that results do not suggest at all that the new coronavirus does not spread in the warmer regions. Therefore, it is critical that each country implements effective public health interventions to slow down the transmission of COVID-19. This is as important as deploying smart city technology to fight the crisis.