Is the New Coronavirus Airborne? A Study From China Finds Evidence
By Joni Sweet
Reducing our risk for COVID-19 depends on how well we understand the way SARS-CoV-2, the virus that causes COVID-19, is transmitted.
Experts believe SARS-CoV-2 mainly spreads from person to person through respiratory droplets released when a person with the virus coughs, sneezes, or talks.
It's also possible that you can contract the virus if your hands come in contact with your mouth, nose, or eyes after touching a contaminated surface.
But can SARS-CoV-2 be spread through the air we breathe?
A new study has found evidence of the virus in the air around two hospitals in Wuhan, China.
While it's still unclear whether you can contract the virus from breathing virus-laden air, the latest findings could make an impact on how we protect ourselves as states begin to open up.
Coronavirus Material Found in the Air
In a report published April 27 in the journal Nature, researchers measured the concentration of genetic material known as RNA from the new coronavirus in samples collected in February and March from 30 spots in and around two COVID-19 treatment hospitals in Wuhan.
One hospital was dedicated to treating patients with severe cases of the disease, while the other was a makeshift field hospital used to quarantine and treat people with mild symptoms.
The investigators found higher concentrations of material from the virus in samples collected in areas prone to crowding, certain intensive care units, and places with poor airflow, like bathrooms.
Areas where medical staff removed protective apparel were found to have elevated concentrations of viral material, which may indicate that SARS-CoV-2 can be resuspended in the air when staff take off their apparel.
Sites that were rigorously sanitized, well-ventilated, and uncrowded were found to have low or undetectable concentrations of viral RNA in aerosol samples.
Can You Contract the Virus From the Air?
A World Health Organization scientific brief from March 29 found that there were no reports of airborne transmission of the new coronavirus.
While the recent Nature study didn't look at whether airborne viral material can infect someone, the findings indicate the need for further research on the possibility of contracting the new coronavirus from air contaminated with viral material.
"If you think about aerosol transmission in medicine, the chickenpox can be transmitted just by someone having been in a room where someone [with the virus] was breathing before they had any symptoms," said Dr. Natasha Lewry Beauvais of Northern Virginia Family Practice. "The typical cold virus is not transmitted that way."
The size of the particles may make a difference in whether the virus can infect someone, says Dr. Jill Grimes, a board certified family physician and author of "The Ultimate College Student Health Handbook."
The respiratory droplets believed to spread COVID-19 are around 5 microns, while the aerosolized SARS-CoV-2 in the study were as small as a quarter of a micron in size.
"The problem with aerosolized particles is that they're teeny tiny. How many particles does it take to infect someone? We don't know the answer to that," Grimes said.
Wearing a mask can help you avoid inhaling infected droplets and releasing them into the air if you happen to be carrying the virus.
Cotton fabric, often used for homemade cloth masks, have pore sizes between 50 and 100 microns, according to an article from Grimes.
She recommends wearing masks made from at least two layers of fabric and inserting a coffee filter between them for more protection.
"Those cloth masks need to be washed after you wear them, at least every day," Grimes added.
How to Protect Yourself as States Reopen
Taking precautions around the known ways that the new coronavirus spreads can help keep you safe as states begin to reopen.
While it's clear that small amounts of SARS-CoV-2 material may be in the air, doctors say the biggest risk of contracting the new coronavirus come from person-to-person transmission and, to a lesser degree, contact with contaminated surfaces or objects.
Even though the recent Nature study showed that well-ventilated areas have lower concentrations of airborne SARS-CoV-2, that doesn't necessarily mean it's significantly safer to dine outdoors than inside a restaurant.
"The hard science is on droplet transmission," Beauvais said. "In a restaurant, people take off their masks to eat and drink, and people can release droplets when they laugh, sneeze, or cough — even without being sick."
She adds that the risk of spreading and contracting the virus is on a continuum based on environment (crowded places may be more dangerous than spots where you can practice physical distancing) and people's attentiveness to things like handwashing and wearing masks.
Just because your state is opening up doesn't necessarily mean it's completely safe to resume all normal activities, says Dr. Matthew Heinz, hospitalist and internist at Tucson Medical Center.
"Follow the recommendations of public health officials and qualified scientists, not politicians or social media. The folks who have helped squash Ebola and H1N1 really know this stuff," Heinz said. "This is an insidious ninja virus that hasn't gone anywhere. It's still doing its job."
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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.
"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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