Saturday, April 18, 2020

Will Summer Sunshine Suppress Coronavirus Pandemic?

Preliminary results of a US Government study reveal that the sunlight quickly destroys COVID19, the novel coronavirus. The study found that the risk of “transmission from surfaces outdoors is lower during daylight” and under higher temperature and humidity conditions, according to Yahoo News. This latest work reinforces the conclusions of "Will Coronavirus Pandemic Diminish by Summer?", a recent paper written jointly by Pakistani and Indian researchers at Massachusetts Institute of Technology. Ultraviolet (UV) light, a component of sunlight, has long been known to be an effective disinfectant.

Homeland Security Study: 

The study by US Department of Homeland Security scientists concludes that “sunlight destroys the virus quickly” but it also warns that enclosed areas with low humidity, such as airplane cabins, “may require additional care to minimize risk of transmission. ”Simulated sunlight “rapidly killed the virus in aerosols,” the study says, while without that treatment, “no significant loss of virus was detected in 60 minutes. ”While the DHS describes the results as preliminary, they may eventually make their way into specific recommendations. “Outdoor daytime environments are lower risk for transmission,” the briefing states.

Dr. Qasim Bukhari's Work: 

Dr. Qasim Bukhari, a Pakistani-American scientist at MIT,  told Yahoo News that since he and his colleagues published that analysis, the numbers on the coronavirus’s spread continue to support their contention. “They are doing a lot of tests now in India. Also, when you look at the numbers in Pakistan it’s the same. There are more than 5,000 cases in Pakistan right now,” he said. “But the increase is not as rapid as you see in other countries.”

Last month I followed up with Dr. Qasim Bukhari, a fellow NED University alumnus from Karachi, about his findings. Here's a brief Question/Answer version of the email exchange I had with Dr. Bukhari:

 RH: My understanding from the data I have seen from various sources is that the coronavirus transmission rates decline but do not necessarily go to zero in hot and humid weather. And the reason is that the fatty outer layer of the virus has trouble in heat and humidity. Is that accurate?

QB: That would be almost accurate. The only thing we don't know so far is, how much decline in growth rate we are talking about. It is definitely non-zero. The underlying reasons may be many or either of many. One reason could be the fatty outer layer reason that you mentioned. Other reason could be the antibacterial nature of sunlight, another reason could be low indirect transmission (through air) in high humidity.

"There is indeed evidence that weather plays a role, but in no way we are suggesting that this role alone would be so decisive as to completely halt the spread of COVID. And anyway, the affect of this weather would only be relevant in humid hot countries. Please do share, but please use the right words that properly communicate that it is incredibly important to take precautions and quarantine measures even in the most humid hot regions, as the spread would keep on going without that, we have evidence from Singapore, Malaysia and Indonesia of this."

Over 90% of Coronavirus Cases So Far in Red Zone. Source: Dr. Qasim Bukhari and Dr. Yusuf Jamil 

Wang, Weifeng, Beihang and Ke Tang: 

There is similar work that has recently been published by a Chinese research team that included Jingyuan Wang, Kai Feng, Weifeng Lv of Beihang University, and Ke Tang from Tsinghua University. They studied 100 different Chinese cities that each reported more than 40 cases of COVID-19 from Jan. 21 to 23, 2020.

“In the early dates of the outbreaks, countries with relatively lower air temperature and lower humidity (e.g. Korea, Japan and Iran) saw severe outbreaks than warmer and more humid countries (e.g. Singapore, Malaysia and Thailand) do," the researchers wrote.

COVID-16 Transmission Rates Vs Temperature and Humidity

Here's an excerpt from the abstract published by the team:

"After estimating the serial interval of COVID-19 from 105 pairs of the virus carrier and the infected, we calculate the daily effective reproductive number, R, for each of all 100 Chinese cities with more than 40 cases. Using the daily R values from January 21 to 23, 2020 as proxies of non-intervened transmission intensity, we find, under a linear regression framework for 100 Chinese cities, high temperature and high relative humidity significantly reduce the transmission of COVID-19, respectively, even after controlling for population density and GDP per capita of cities. One degree Celsius increase in temperature and one percent increase in relative humidity lower R by 0.0383 and 0.0224, respectively. This result is consistent with the fact that the high temperature and high humidity significantly reduce the transmission of influenza. It indicates that the arrival of summer and rainy season in the northern hemisphere can effectively reduce the transmission of the COVID-19."

Some experts are pointing to the increased amount of UV rays from the sun the Northern Hemisphere will be subject to this time of year as a factor that could slow the virus, according to a story in AccuWeather.

Dr. Anthony Fauci On Effect of Weather:

Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases (NIAID) who also serves on the White House coronavirus task force, has acknowledged that a change of season might affect COVID transmission rates.

Here's what he said at a recent White House briefing: “I think it (weather) very well might. And the reason I say that is that what we’re starting to see now in the Southern Hemisphere, in southern Africa and in the southern hemisphere countries, is that we’re having cases that are appearing as they go into their winter season. And if, in fact, they have a substantial outbreak, it will be inevitable that we need to be prepared, that we’ll get a cycle around the second time.”


A US Government study has found that the sunlight quickly destroys the coronavirus. Ultraviolet (UV) light, a component of sunlight, has long been known to be an effective disinfectant.  Mainstream US and Indian media have also widely covered a recent MIT paper on the effects of heat and humidity on coronavirus transmission. Dr. Qasim Bukhari, the lead author and alumnus of NED University located in Karachi, Pakistan, has shared data showing that 90% of the coronavirus cases so far have occurred  in a regions with absolute humidity between 4 and 10 grams per cubic meter. Recent Chinese research is also showing that hot and humid weather may significantly slow down transmission of coronavirus or COVID-19. An increase of just one degree Celsius and 1% relative humidity increase substantially lower the (Covid-19  or 2019-nCoV) virus’s transmission, says a study published on March 10, 2020 by Chinese researchers. One possible reason is that the fatty outer layer of the virus has trouble surviving in high heat and humidity. The virus disintegrates when the fatty outer cover is gone in a way similar to how the soap and hot water destroy it. This may explain why there appear to be relatively few reports of local COVID-19 transmissions in places like Pakistan. Most of the known coronavirus cases in Pakistan appear to be those of the people who have come into the country from cold, dry places like northern Iran where the pandemic is raging. The rate of local transmission in Pakistan is not zero but relatively low. Dr. Bukhari says that "there is indeed evidence that weather plays a role, but in no way we are suggesting that this role alone would be so decisive as to completely halt the spread of COVID."

Related Links:


Mayraj F. said...
Coronavirus Can Survive High Temperatures for Long Periods, Study Finds

Riaz Haq said...

Mayraj: "Coronavirus Can Survive High Temperatures for Long Periods"

No virus survives for long under UV light which is part of sunlight.

UV light is a strong disinfectant.

Mayraj F. said...

Florida has sunlight and its cases are mounting.
Florida COVID-19 cases, deaths rise as model predicts peak has passed

Riaz Haq said...

Mayraj: "Florida has sunlight and its cases are mounting."

Florida cases raise the following questions:

1. How many of these are local transmissions?

2. Did these local transmissions occur indoors or outdoors?

Riaz Haq said...

#SouthAsia has 20% of world’s population but less than 2% of #COVID19 cases. Positive Test Rates Percent: #India (4.36), #Bangladesh (11.43), #Pakistan (8.26) much lower than #Italy (12.69), #US (19.55), #France (34.09). #Sunshine #Heat #Humidity #BCG

Despite being home to one-fifth of the world’s population, South Asia accounts for less than 35,000, or approximately 1.5 per cent, of the 24 lakh coronavirus cases worldwide.

The eight countries, which make up the Indian subcontinent and are part of the South Asian Association for Regional Cooperation (SAARC), include Afghanistan, Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan, and Sri Lanka.

While the number of cases in Europe and North America was 14 lakh and 8.8 lakh, respectively, as of 22 April, India had 20,178 cases, Pakistan 9,749, Bangladesh 3,382, Afghanistan 1,092, Sri Lanka 321, Maldives 108, Nepal 42 and Bhutan 6.

Even the positivity rate — the ratio of confirmed cases to total tests conducted — is lower in South Asia. The rates in India (4.36), Bangladesh (11.43), Pakistan (8.26) and Sri Lanka (4.19) are way lower than those for Italy (12.69), US (19.55), France (34.09) and Germany (8.59).

Experts have offered different reasons to explain this disparity — the warmer and more humid weather in the South Asian region tempered the spread of the disease, protection offered by the tuberculosis vaccine bacillus Calmette-GuĂ©rin (BCG), a potentially better immune response among those in the Indian subcontinent, and a weaker strain of the virus here.

Some say the explanation could be a lot simpler — South Asian countries have likely implemented efficient physical distancing thanks to a slower first wave of spread within the countries. The nations are also reportedly seeing far lower testing numbers as compared to the rest of the world.

The SAARC countries have the lowest testing rates in the world but that may not fully explain the fewer cases.

India, for instance, conducts just 335 tests per million population whereas the numbers for western are far higher — 7,103 in France, 20,629 in Germany, and 12,659 in the US.

But even in countries of South Asia that have higher testing, the positivity rate has remained low. Bhutan has conducted a total of over 8,700 tests, which translates to 11,000 tests per million people, but has only six confirmed cases. The Maldives is currently conducting 6,871 tests per million with 1.08 positivity.

“At this point in time, no one has an explanation for the low prevalence of cases in this region,” said Sumanth C. Raman, a healthcare domain consultant and a doctor specialising in child health. “Certainly the rate of testing is lower, and that is a very likely contribution to the explanation. But it doesn’t explain the full picture.”

The lockdown may have “shifted the peak from say April to June” but only time will tell if South Asian countries indeed have an advantage, said Shahid Jameel, a virologist who serves as the CEO of The Wellcome Trust/DBT India Alliance, an independent nonprofit that funds health and biomedical research in Indian institutions.

“It (the number of cases), however, has definitely proven the doomsday predictors wrong. They had predicted the number of infected as high as 1-2 crore,” he said.

A major reason for the observed pattern of spread could be the fact that older populations respond poorly to Covid-19, said Madhukar Pai, director of Global Health at McGill University, Canada, and a tuberculosis expert. “Countries with younger populations should have a different epidemic curve because of the age effect, especially for deaths due to Covid-19,” he said.

Younger people have mild or asymptomatic infection and, over time, they will protect others through herd immunity, Pai said.