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Coronavirus May Wane This Summer, but Don’t Expect the Pandemic to End

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Coronavirus May Wane This Summer, but Don’t Expect the Pandemic to End
An aerial view of a notice dug into the sand reading #STAYHOME on Tamarama Beach on April 02, 2020 in Sydney, Australia. James Gourley / Getty Images

By Ellen Wright Clayton

Will SARS-CoV-2, the virus that causes COVID-19, fade away on its own this summer?

After all, other viruses – including influenza and respiratory syncytial virus (RSV), which causes bronchiolitis in little children – are mostly seen in the winter.


The National Academies' Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats recently addressed the question of whether SARS-CoV-2 will follow the same pattern. The group of experts corralled the research that's been done so far – much of it not yet peer-reviewed – to assess the evidence.

While there is some reason to hope that things may get better as the weather warms up, there is plenty of reason for the U.S. to keep its guard up.

Are Heat and Humidity Reason for Hope?

Although the U.S. is early in the course of the pandemic, there is evidence from other countries that SARS-CoV-2 spreads more rapidly in cold, dry weather.

One preprint study of 30 Chinese provinces showed that the number of COVID-19 cases went down by between 36% and 57% for every 1.8 degree Fahrenheit increase in temperature. When temperatures held steady in the low 40s F, the number of cases went down between 11% and 22% with each 1% increase in relative humidity (how much water is in the air).

A larger preprint study looking at 310 regions in 116 countries found that 11% more cases were reported when the temperature went down 9 degrees, the relative humidity went down 10% and when the wind speed went up.

Laboratory research also suggest that the virus survives longer in cold conditions. One study showed that SARS-CoV-2 lasts for 14 days at 40 F in lab media but is gone after one day at 98.6 F.

These and other studies suggest that warm, humid weather may slow the spread of this virus, although not all commentators agree.

New research on this topic appears almost daily, and scientists are watching to see what happens as summer comes to the Northern Hemisphere.

Which Clues Call for Caution?

COVID-19 is already spreading in many parts of the world where it's hot, including Australia and South America, demonstrating that high temperatures are not enough to stop the disease.

The most important reason to be concerned about ongoing spread is the fact that this is a brand new virus for humans, so almost everyone is susceptible to being infected.

In fact, weather actually appears to play a minor role in the rate at which this virus spreads.

Other influences on infection rates include individual behaviors, cultural practices, geography, income and living conditions. Public health practices such as social distancing, the intensity of testing for infection, contact tracing, quarantine of people who are exposed and isolation of people who are actually infected also play a big role in how the coronavirus spreads.

The news from other viral diseases is not encouraging either. The two most serious coronavirus diseases that are closely related to COVID-19, the first SARS outbreak and MERS, did not vary with the seasons after they emerged. In fact, MERS is still found year-round in the Middle East, where it is hot and dry. Pandemic influenza infections have emerged at different times of the year as well.

What Should We Do?

The long-term solution to SARS-CoV-2 will be to develop a safe and effective vaccine. This work is proceeding at unprecedented speed, but it will still take anywhere from months to a few years and will require trials involving thousands of people and massive international leadership and collaboration.

Until there's a vaccine, prevention will require avoiding exposure to people who can spread the virus. Communities need to test people to find out who is contagious and engage in serious contact tracing, quarantine and isolation. Scientists need to learn more about how to determine if someone is immune and how long immunity lasts, a big open question at the moment. As individuals, each of us will need to follow expert scientific advice about good hygiene practices and distancing.

SARS-CoV-2 is likely to keep circulating until the human population has widespread immunity, which hopefully will come not from an unchecked pandemic but from developing and deploying a safe and effective vaccine.

Ellen Wright Clayton is a Professor of Pediatrics and Law and Health Policy at Vanderbilt University.

Disclosure statement: Ellen Wright Clayton reviewed the statement on seasonality by the NASEM Standing Committee.

Reposted with permission from The Conversation.


A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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