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August 12, 2020

Infectious coronavirus can linger in the air, a new study shows

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    A new, preprint study reveals that researchers isolated viable samples of the novel coronavirus from respiratory droplets that were hanging in the air of a hospital room, leading experts to question what the findings mean for how the virus spreads.

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    US new coronavirus cases near 5.2M, deaths top 164K

    The new findings come as U.S. officials on Tuesday reported about 53,344 new cases of the novel coronavirus, bringing the total number of coronavirus cases reported in the country since the epidemic began to 5,154,700 as of Wednesday morning—up from 5,101,300 cases reported as of Tuesday morning.

    Data from the New York Times shows that Guam, Puerto Rico, the U.S. Virgin Islands, and four states saw their average daily numbers of newly reported coronavirus cases rise over the past 14 days: Hawaii, Illinois, Massachusetts, and South Dakota.

    The Times' data also shows that the average daily numbers of newly reported coronavirus cases over the past two weeks remained mostly stable in Washington, D.C., and 22 states: Arkansas, California, Connecticut, Georgia, Idaho, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Montana, Nebraska, New Jersey, New York, North Dakota, Oregon, Rhode Island, Texas, Vermont, Virginia, and Wisconsin.

    Although its number of newly reported coronavirus cases has remained steady over the past two weeks, Texas on Tuesday became the third state to report a total of more than 500,000 cases of the virus since America's epidemic began, with a total of 522,626 reported cases as of Wednesday morning. California and Florida are the only other states so far that have reported more than 500,000 cases of the virus.

    However, data from Texas' Department of Health Services shows that the percentage of coronavirus tests performed in the state that are positive has increased to 24% over the past seven days, which is the highest positivity rate the state has seen since the epidemic started, the Associated Press reports. Gov. Greg Abbott (R) said he thinks family and neighborhood gatherings are driving the increase.

    "There's a reason why this is happening, I believe, and that is some people feel if they're just with family members," they can let down their guard, Abbott said. "And that turns out not to be the case."

    Abbott on Tuesday said Texas' coronavirus infection rate and the rate of hospitalizations tied to the virus in the state remain too high for the state to move forward with reopening nonessential businesses and easing other measures aimed at curbing the virus' spread.

    "The most important thing I can convey today is that even though the numbers of Covid-19 have improved," the coronavirus "not left the state of Texas," Abbott said.

    Meanwhile, the Times' data shows that 24 states saw their average daily numbers of newly confirmed coronavirus cases decrease over the past 14 days: Alabama, Alaska, Arizona, Colorado, Delaware, Florida, Louisiana, Maine, Maryland, Mississippi, Missouri, Nevada, New Hampshire, New Mexico, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Utah, Washington, West Virginia, and Wyoming.

    U.S. officials also reported about 1,450 new deaths tied to the coronavirus on Tuesday, bringing the country's total of reported coronavirus-linked deaths since the epidemic began to 164,468 as of Wednesday morning—up from 163,018 deaths reported as of Tuesday morning.

    According to the Times' data, Puerto Rico and 20 states saw their average daily numbers of newly reported deaths linked to the coronavirus rise over the past 14 days: Arkansas, California, Florida, Georgia, Hawaii, Iowa, Louisiana, Maryland, Minnesota, Mississippi, Nebraska, Nevada, North Carolina, North Dakota, South Dakota, Tennessee, Texas, Virginia, Washington, and West Virginia.

    On Tuesday, Florida and Georgia each reported record-high single-day increases in their numbers of new deaths linked to the coronavirus.

    Study shows viable coronavirus can hang in the air

    As the coronavirus has continued to spread throughout the United States, researchers have scrambled to identify exactly how the virus transmits.

    The World Health Organization (WHO) largely has maintained that the virus primarily spreads through large respiratory droplets that are expelled when an infected person coughs and sneezes—but those droplets typically fall to the ground and do not hang in the air. WHO has been skeptical of whether the coronavirus can spread through smaller, aerosolized droplets, saying that while such transmission is possible, it hasn't been supported with strong evidence. Still, the organization has acknowledged that some outbreak reports indicate the virus can be transmitted in indoor spaces through tiny airborne particles and called for further investigation.

    Now, researchers at University of Florida in the new study—which was published preprint and hasn't yet been peer reviewed—say they have evidence showing that the novel coronavirus can, in fact, hang in the air in smaller, aerosolized droplets.

    For the study, the researchers collected two separate aerosol samples—one from a distance of seven feet and another from a distance of 16 feet—from hospitalized patients with Covid-19, the disease caused by the coronavirus.

    The researchers gathered the samples inside a hospital room within a ward designated for Covid-19 patients at the University of Florida Health Shands Hospital. The hospital rooms underwent six air changes each hour, and they were equipped with efficient filters, ultraviolet irradiation, and other safety measures intended to deactivate any coronavirus samples present in the room before new air was pumped into the space.

    The researchers collected the samples in a manner similar to how humans would inhale aerosolized biological material. To do so, they developed a sampler that used pure water vapor to expand aerosols to a point that they could be easily gathered from the air. The sampler then transferred the aerosols into a solution designed to preserve any pathogens present in the samples.

    The researchers were able to isolate viable samples of the novel coronavirus from the aerosols, finding 74 particles of the virus per liter of air. John Lednicky, the research team's lead virologist, said the hospital's safety measures appeared to help reduce the coronavirus' presence in the samples, noting that the aerosols contained fewer virus particles than the researchers would expect to see in samples gathered from other indoor spaces without as robust ventilation, such as a school.

    Still, the researchers found that the coronavirus particles they isolated from the aerosol samples could infect cells in a lab dish. They also found that the genome sequence of the coronavirus particles they had isolated was identical to the sequence of coronavirus particles they collected with a swab from one of the Covid-19 patients in the hospital room where they gathered the samples.

    Ultimately, the researchers wrote that their findings show "[p]atients with respiratory manifestations of Covid-19 produce aerosols in the absence of aerosol-generating procedures that contain viable" coronavirus particles. Further, they added that the findings suggest "these aerosols may serve as a source of transmission of the virus."

    What do the findings mean for coronavirus transmission?

    Many public health experts touted the new findings, saying they confirm that infectious coronavirus particles can hang in the air.

    For example, Linsey Marr, a professor of civil and environmental engineering at Virginia Tech, told the Times, "This is what people have been clamoring for. It's unambiguous evidence that there is infectious virus in aerosols."

    Separately, Marr in a tweet posted last week wrote, "If this isn't a smoking gun, then I don't know what is."

    But others raised questions about whether the findings could be extrapolated to estimate a person's risk of contracting the coronavirus from those aerosolized particles.

    "I'm just not sure that these numbers are high enough to cause an infection in somebody," said Angela Rasmussen, a virologist at Columbia University. "The only conclusion I can take from this paper is you can culture viable virus out of the air," she said. However, Rasmussen added, "that's not a small thing."

    Seema Lakdawala, a respiratory virus expert at the University of Pittsburgh, said the study's results should encourage people to take precautions to prevent the coronavirus' transmission, such as improving indoor ventilation.

    Robyn Schofield, an atmospheric chemist at Melbourne University in Australia, said the findings also show that practicing six feet of physical distancing when indoors does not offer the same level of protection as it does when people are outdoors.

    "We know that indoors, those distance rules don't matter anymore," she said, explaining that the six-feet minimum for physical distancing is "misleading, because people think they are protected indoors and they're really not" (Weber, Associated Press, 8/12; New York Times [1], 8/12; Owens, "Vitals," Axios, 8/12; Mandavilli, New York Times, 8/11; New York Times [2], 8/12; Lednicky et al., medRxiv, 8/3).

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