Explainer: Summer might slow coronavirus but is unlikely to stop it

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Explainer: Summer might slow coronavirus but is unlikely to stop it

By Kate Kelland, Manas Mishra and Christine Soares

 

FILE PHOTO: With the coronavirus disease (COVID-19) restrictions eased, visitors enjoy the beach during the Memorial Day holiday weekend, the unofficial start of summer, in Ocean City, Maryland, U.S., May 23, 2020. REUTERS/Kevin Lamarque/File Photo

 

(Reuters) - The arrival of warmer weather in the Northern Hemisphere raises the question of whether summer could slow the spread of the coronavirus outbreak. Here is what science says.

 

While warmer weather typically ends the annual flu season in temperate zones, climate alone has not stopped the COVID-19 pandemic from sweeping any part of the globe. In fact, outbreaks in hot and sunny Brazil and Egypt are growing.

 

Still, recent data about how sunlight, humidity and outdoor breezes affect the virus gives some reason for optimism that summer could slow the spread.

 

IS THE NEW CORONAVIRUS 'SEASONAL'?

The virus has not been around long enough to be certain.

 

Respiratory infections like flu and the common cold follow seasonal patterns in temperate regions. Environmental conditions including cold weather, low indoor humidity, and spending more time indoors can all hasten the spread of an epidemic.

 

Real-world evidence about the effect of weather on the new virus is mixed. One study of 221 Chinese cities found that temperature, humidity and daylight did not affect speed of spread.

 

Two other studies did find an effect, including a look at new infections in 47 countries that linked higher temperatures to slower transmission in places like the Philippines, Australia and Brazil.

 

"The Northern hemisphere may see a decline in new COVID-19 cases during summer and a resurgence during winter," concluded the authors of another study of 117 countries, which found that each 1-degree of latitude increase in distance from the Equator was associated with a 2.6% increase in cases.

 

WHY DO RESPIRATORY DISEASES SPREAD DIFFERENTLY IN SUMMER AND WINTER?

"The reason why cold weather is presumed to cause spreading of coughs, colds and flu is that cold air causes irritation in the nasal passages and airways, which makes us more susceptible to viral infection," said Simon Clarke, an expert in cellular microbiology at Britain's University of Reading.

 

Winter weather tends to inspire people to spend more time indoors, although air conditioning may also bring people back inside in the summer.

In the lab, when temperatures and humidity rise, coronavirus particles on surfaces more quickly lose their ability to infect people - and they are inactivated especially fast when exposed to sunlight, U.S. government researchers found.

 

It is still a good idea for people to wash hands frequently, practice social distancing and wear a mask in summer, experts say. While virus particles coughed or exhaled by an infected person will disperse faster outdoors, one study found a gentle breeze could carry saliva droplets up to 6 meters (19.69 feet).

 

WHAT ELSE ABOUT SUMMER COULD SLOW THE VIRUS?

Vitamin D : Researchers are investigating whether levels of immunity-regulating vitamin D in people's blood affect how vulnerable they are to infection with the new coronavirus or how sick they become. The majority of vitamin D in the body comes from skin exposure to sunlight.

 

Pollen: A study in the Netherlands of all "flu-like" illness, including COVID-19, in recent years concludes that pollen concentrations are a better predictor than sunlight of respiratory disease trends. Clouds of pollen act as air filters, snagging virus particles, and pollen activates immune responses, even in people without overt allergies.

 

The study found that flu-like illness started to drop when pollen in the air reached 610 grains per cubic meter, a typical level from early spring to October in most middle latitudes.

 

(This story corrects to reflect a 2.6% increase rather than 2.6% drop in cases, paragraph 9)

 

(Reporting by Kate Kelland in London, Manas Mishra in Bengaluru and Christine Soares in New York; Editing by Peter Henderson and Matthew Lewis)

 

-- © Copyright Reuters 2020-06-11

 

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[AlexRich]

We just have to let it rip, protect the vulnerable, but don’t allow it to reek any further economic damage. 

[Tug]

22 minutes ago, AlexRich said:

We just have to let it rip, protect the vulnerable, but don’t allow it to reek any further economic damage. 

Oh it will rip all right we don’t have much choice about that but I agree we must do all we can to mitigate health and economic damage I wish we were seeing more shared information acrosst borders and keeping the politics out of it

[balo]

Nonsense, look at Brazil now, the worst hit country in the world.  It's a tropical climate with average temperatures around 30 degrees C.  This virus does not care if it's hot or cold outside. 
All that matters is good hygiene and always keep 1-2 meter distance to people. 

[Proboscis]

3 hours ago, balo said:

Nonsense, look at Brazil now, the worst hit country in the world.  It's a tropical climate with average temperatures around 30 degrees C.  This virus does not care if it's hot or cold outside. 
All that matters is good hygiene and always keep 1-2 meter distance to people. 

What makes Brazil the worst hit country right now is down to many factors, probably including population density and poor sanitation. Brazil is entering the coolest time of the year which is not helping.

 

Looking around the world, I cannot help noticing that countries such as SE Asia (Laos, Vietnam, Cambodia and Thailand) have all done remarkably well without extreme efforts. Russia did very well at the beginning, possibly due to the very low temperatures, but less well now.

 

Another seasonal factor might be pollen - the presence of pollen might make the virus more inactive as it sticks to the pollen. Pollen is often associated with warmer times of the year.

 

No one is claiming that the virus is going to disappear in the summer but, like all corona-type viruses before, it appears to be less infectious during the summer time.

[Nigel Garvie]

3 hours ago, balo said:

Nonsense, look at Brazil now, the worst hit country in the world.  It's a tropical climate with average temperatures around 30 degrees C.  This virus does not care if it's hot or cold outside. 
All that matters is good hygiene and always keep 1-2 meter distance to people. 

No doubt about Brazil's high number of cases. That nutter Bolsonaro closed down the reporting site so people would stop seeing how bad it was. However statistically Brazil is an outlier, their government policies were useless, considerably worse even than Trump and Johnson.

 

There is clearly a heat factor in winter colds and flu, why not Covid-19, which is part of the same family as the common cold. I think the information that it gets inactivated when lying on hot surfaces appears valid. 

[rabas]

Another opinion.

 

Surprisingly, in 1918 they understood in detail how to fight the flu, from air-tight goggles, gloves, masks, self-isolation, touching things, cleaning, and even putting patients in sunlight and opening windows for fresh air. They had instructions how to lay your food tray outside your bedroom door when self isolating in your own home. All this information was usually printed on a single piece of paper.

 

Compare that with today's information of mass confusion. Yet now we know so much more.

 

Edited June 11, 2020 by rabas

[Sheryl]

It is never summer worldwide.

 

In the southern hemisphere, it is now winter.

 

We can see where it is and is not slowing, and it is slowing in many northern countries where it peaked between Jan - April.  The big question is, will there be a second wave in these same countries come winter? That is what happened with the Spanish Flu and the second wave was worse than the first.

[phantomfiddler]

2 hours ago, Sheryl said:

It is never summer worldwide.

 

In the southern hemisphere, it is now winter.

 

We can see where it is and is not slowing, and it is slowing in many northern countries where it peaked between Jan - April.  The big question is, will there be a second wave in these same countries come winter? That is what happened with the Spanish Flu and the second wave was worse than the first.

I could never understand that either, sort of like a Thermos flask. Put hot coffee inside and it keeps it hot, but put an iced drink in and it keeps it cold. How does it know !!!

[johnpetersen]

4 hours ago, Sheryl said:

It is never summer worldwide.

 

In the southern hemisphere, it is now winter.

 

We can see where it is and is not slowing, and it is slowing in many northern countries where it peaked between Jan - April.  The big question is, will there be a second wave in these same countries come winter? That is what happened with the Spanish Flu and the second wave was worse than the first.

In the USA, the decline is mainly due to the states that were severely afflicted and have maintained strict lockdown measures. But in states that were slow to lockdown and/or quick to exit from that, there has been a sharp increase in cases.

 

As coronavirus cases rise nationwide, public health experts urge caution

https://www.washingtonpost.com/sports/as-coronavirus-cases-rise-nationwide-public-health-experts-urge-caution/2020/06/10/1617dee4-ab36-11ea-a9d9-a81c1a491c52_story.html

 

Arizona is on the verge of a health emergency:

Arizona calls for emergency plan as COVID-19 spikes after reopening

https://www.reuters.com/article/us-health-coronavirus-usa-arizona/arizona-calls-for-emergency-plan-as-covid-19-spikes-after-reopening-idUSKBN23H03K