The post Aerosols, Droplets, Fomites: What We Know About Transmission Of COVID-19 appeared first on Virus Reports.
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A sneeze can carry the coronavirus pathogen in droplets and in aerosols — and they could land on a surface, making it a fomite.
Peter Dazeley/Getty Images
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Peter Dazeley/Getty Images
A sneeze can carry the coronavirus pathogen in droplets and in aerosols — and they could land on a surface, making it a fomite.
Peter Dazeley/Getty Images
By now, it’s common knowledge that the coronavirus can be spread by being in close contact with someone who’s infected and then breathing in their respiratory droplets. Or by touching a contaminated surface and rubbing your eyes, nose or mouth.
An open letter signed by 239 researchers addressed to the World Health Organization, published Monday in Clinical Infectious Diseases, calls for attention and guidance around a third route of transmission: tiny respiratory particles that float in the air and are called aerosols. They could be responsible for infecting someone who comes along and breathes them in.
Researchers are actively debating the importance of aerosol transmission and whether precautionary approaches should be taken even without clear answers about its role in the spread of the coronavirus.
“The ratio is something we need to figure out,” says Kimberly Prather, an atmospheric chemist at Scripps Institution of Oceanography, who signed the letter to WHO.
Here’s what we know about the different modes of transmission:
Droplet
What it is: A microscopic virus-filled particle of breath or spittle, around 5 to 10 microns — about the size of a red blood cell — that comes out of the nose or mouth of an infected individual when they breathe, speak, cough or sneeze. Droplets generally fall to the ground within a few feet of the person who expels them.
How a virus could spread this way: Through what researchers call “the respiratory route.” Virus-laden droplets are expelled from the nose or mouth of an infected person and find their way into nearby eyes, noses and mouths, “like if you’re standing next to your kid and they cough in your face,” says Seema Lakdawala, a flu researcher at the University of Pittsburgh.
How much does it contribute to the spread? Directly coming into contact with respiratory droplets is currently considered the most frequent mode of transmission, according to the U.S. Centers for Disease Control and Prevention and WHO.
Aerosol
What it is: A virus-packed particle, smaller than 5 microns, that’s also expelled from an infected person’s mouth when breathing, speaking, coughing or sneezing. Unlike a droplet, smaller aerosol particles can remain suspended in the air.
“They’ll continue to float and follow the air streams in a room,” Prather says.
How a virus could spread this way: Through the respiratory route in which a person breathes in clouds of tiny virus particles that have accumulated and may be traveling on air currents.
How much does it contribute to the spread? It’s an open question that begs more research. “Aerosols probably have some contribution toward spread, but we don’t know to what extent and what situations are most relevant,” says Abraar Karan, a physician at Harvard Medical School who treats coronavirus patients. Viral spread via air currents has been documented in certain indoor environments: at a restaurant in Guangzhou, China, where people sitting downstream from an air conditioner caught COVID-19, and at a March choir practice in Washington state, where many choir members got sick with coronavirus after likely breathing in tiny airborne particles generated by individuals who were infected but symptom-free at the time. What’s still unclear is how long the virus lingers in the air, how far it travels (possibly through a room but not down the street) and how commonly it spreads this way.
Fomite
What it is: An object covered with virus particles, possibly because someone recently sneezed or coughed respiratory droplets onto it, or swiped a germ-covered hand on it. A countertop or a phone could become a fomite in that same manner. The particles could survive from several hours to several days.
How a virus could spread this way: Through indirect transmission if people touch the surface of a virus-covered object, pick up the virus on their hands and then introduce the virus to their eyes, nose or mouth.
How much does it contribute to the spread?: The CDC describes this as a “possible” route of coronavirus transmission but maintains that close contact between people is thought to be responsible for most new infections.
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]]>The post Speech droplets that linger in air up to 14 minutes may spread virus — study appeared first on Virus Reports.
]]>According to a new study, speech can generate thousands of mini-droplets that, in a closed environment, can hang in the air for up to 14 minutes and lead to transmission of the novel coronavirus, SARS CoV-2.
The research was published this past week in The Proceedings of the National Academy of Sciences, a peer-reviewed multidisciplinary scientific journal and the official journal of the US National Academy of Sciences. According to the study, speech droplets by asymptomatic carriers “are increasingly considered to be a likely mode of disease transmission.”
Normal speaking can produce “thousands of oral fluid droplets with a broad size distribution,” wrote the American researchers.
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The scientists at the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania conducted a study where they tracked bursts of droplets produced by volunteer speakers and illuminated them using laser lights. The participants spoke through the open end cardboard box and were asked to repeat the words “stay healthy” several times to trace and measure the droplets.
“Whereas large droplets fall quickly to the ground, small droplets can dehydrate and linger as ‘droplet nuclei’ in the air, where they behave like an aerosol,” the study found, adding that they can stay in the air between eight and 14 minutes.
Two men sitting on different benches speak as they keep social distance at a seaside of Glyfada suburb, near Athens, May 15, 2020 (AP Photo/Petros Giannakouris)
The research revealed an average droplet emission rate of 1,000 per second, with up to 10,000 droplets per second depending on speech volume. Certain sounds, such as the “th” in healthy, produced more droplets than others, according to the study.
“These observations confirm that there is a substantial probability that normal speaking causes airborne virus transmission in confined environments,” the researchers wrote.
The study was conducted in a controlled environment and did not involve participants with COVID-19.
Surveys suggest Vitamin D may help
Meanwhile, a study pre-published last month by a group of researchers from Northwestern University in Illinois found a correlation between insufficient Vitamin D and the more serious effects of COVID-19.
Defying COVID-19 restrictions, Israelis enjoy the beach in Tel Aviv, as temperatures rise to 40 degrees in some parts of the country, May 16, 2020. (Miriam Alster/Flash90)
Those with severe Vitamin D deficiencies were found to suffer serious effects from COVID-19 in 17.3 percent of cases studied, while for those with normal levels the figure was 14.6%, according to the study, which has not yet been peer-reviewed.
Northwestern Prof. Vadim Backman, who led the research, estimated that eliminating vitamin D deficiency could cut the mortality rate in half.
“It will not prevent a patient from contracting the virus, but it may reduce complications and prevent death in those who are infected,” he said.
The study, which has not yet been peer-reviewed, relied on data gleaned from China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, Britain and the US. While researchers were unable to study vitamin D levels directly, they used data on C-reactive proteins from blood samples as a stand-in, noting that a correlation between the two has been found before.
Some scientists have theorized that environmental factors such as heat could affect the virus’s ability to spread, while unfounded claims on social media have led some to believe that sunlight could kill the virus.
That claim got a boost last month when a senior US official said a study had shownd sunlight could quickly destroy the virus and heat and humidity could lower the time it lives on surfaces. That study as well has yet to be evaluated independently, but US President Donald Trump spoke about it enthusiastically during a press conference.
US President Donald Trump points to the sun as he arrives to view the solar eclipse, on August 21, 2017, at the White House in Washington. (AP Photo/Andrew Harnik)
The Northwestern study does not directly link the virus to sunlight, which is a main source of Vitamin D, along with fish, eggs and milk. In general, however, having enough of the vitamin is seen as key to maintaining a healthy immune system.
The researchers found that severely low vitamin levels were more likely to trigger a so-called “cytokin storm,” in which the immune system goes into overdrive in an attempt to destroy the virus and winds up making the patient extremely ill. The cytokin storm is considered a leading factor in fatalities, though researchers have struggled to explain why it only occurs in some people, and why some countries are more badly affected than others.
The Northwestern researchers theorized that the deficiency could explain why the young, who were less likely to have developed an acquired immune system, suffered lower mortality rates.
“While I think it is important for people to know that vitamin D deficiency might play a role in mortality, we don’t need to push vitamin D on everybody,” Backman stressed. “This needs further study, and I hope our work will stimulate interest in this area. The data also may illuminate the mechanism of mortality, which, if proven, could lead to new therapeutic targets.”
Two surveys in Asia that have not undergone peer review have also pointed toward a link between vitamin D deficiency and a severe response to the coronavirus, Newsweek reported. However experts warned of the danger of the use of causal inference in that research, as well as the lack of information on research methods.
Agencies contributed to this report.
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]]>The post Coronavirus droplets travel further than social distancing norms: Study appeared first on Virus Reports.
]]>NEW DELHI: A Canadian study on flu has clear implications for COVID-19, as it found that an unobstructed cough could travel over two metres (six feet) in less than three seconds, and keep going.
First reported by the South China Morning Post on Thursday, the study was led by Canada’s Western University and has been accepted for publication in the journal Indoor Air was done in the 2017-18 flu season – well before the COVID-19 struck.
Coronavirus lockdown: Latest updates
“Even when you are 2.5 metres away, the airflow in the cough can still be moving at 200mm (eight inches) a second,” said Eric Savory, professor from department of mechanical and materials engineering at Western University.
“The very fine droplets are going to remain suspended for a long time, even after four seconds.”
According to the World Health Organisation (WHO), the virus is transmitted through respiratory droplets and contact routes.
Another study this month by an MIT researcher claimed that new coronavirus droplets could travel up to 27 feet as a sneeze or a cough results in a turbulent gas cloud that could contain SARS-CoV-2 droplets.
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In a paper published in the Journal of the American Medical Association (JAMA), Lydia Bourouiba, associate professor at MIT and an expert in fluid dynamics, has suggested to revise social distancing of six feet (2 metres) to limit the risk of exposure as well as currently used surgical and N95 masks which “are not tested for these potential characteristics of respiratory emissions”.
In India, the Health Ministry has asked citizens to ensure physical distancing of minimum 1 metre or three feet.
“Recent work has demonstrated that exhalations, sneezes, and coughs not only consist of mucosalivary droplets following short-range semiballistic emission trajectories but, importantly, are primarily made of a multiphase turbulent gas (a puff) cloud that entrains ambient air and traps and carries within it clusters of droplets with a continuum of droplet sizes,” Bourouiba emphasized.
The locally moist and warm atmosphere within the turbulent gas cloud allows the contained droplets to evade evaporation for much longer than occurs with isolated droplets.
“Under these conditions, the lifetime of a droplet could be considerably extended by a factor of up to 1000, from a fraction of a second to minutes,” said Bourouiba.
Dr Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, however urged caution with the MIT study during a White House briefing.
“This could really be terribly misleading,” he said, adding that it would apply only to people with extremely strong sneezes.
An earlier research by the Centers for Disease Control and Prevention (CDC) revealed that the coronavirus RNA was present even after 17 days on a Diamond Princess cruise ship in Japan.
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