Northwest Arkansas Democrat-Gazette
Airborne spread of virus possible, CDC confirms
The Centers for Disease Control and Prevention acknowledged Monday that people can sometimes be infected with the coronavirus through airborne transmission, especially in enclosed spaces with inadequate ventilation.
The statement from the CDC comes as the head of emergencies at the World Health Organization said an estimated 1 in 10 people worldwide may have been infected by the coronavirus.
The long-awaited update to the CDC webpage explaining how the virus spreads represents an official acknowledgment of growing evidence that under certain conditions, people farther than 6 feet apart can become infected by tiny droplets and particles that float in the air for minutes and hours, and that they play a role in the pandemic.
The update follows an incident last month when the agency removed a draft that
had not gone through proper review and was posted in error. The draft’s wording included a reference to aerosols — tiny droplets that can stay in the air, potentially traveling a significant distance. Officials said the draft was removed because they feared the language could be misinterpreted as suggesting that airborne transmission is the main way the virus spreads.
That is not the case. The CDC says the main way the virus spreads is through close contact with virus-containing droplets — large and small — that are emitted when someone coughs, sneezes, sings, talks, or breathes. When people are in proximity, within 6 feet, they are exposed to the whole spectrum of spray that can cause infection. “It’s not just big goobers, but everything that’s exhaled, big and tiny,” said one CDC scientist who spoke on the condition of anonymity because he was not authorized to speak on the record.
Now, the CDC is saying infection can also spread through exposure to smaller virus-containing droplets and particles that can remain suspended in the air over long distances and time.
“There is evidence that under certain conditions, people with COVID-19 seem to have infected others who were more than six feet away,” the updated web page states. “These transmissions occurred within enclosed spaces that had inadequate ventilation. Sometimes the infected person was breathing heavily, for example while singing or exercising.”
“Under these circumstances,” the web page says, “scientists believe that the amount of infectious smaller droplet and particles produced by the people with COVID-19 became concentrated enough to spread the virus to other people. The people who were infected were in the same space during the same time or shortly after the person with COVID-19 had left.”
In a statement, the agency said it “continues to believe, based on current science, that people are more likely to become infected the longer and closer they are to a person with COVID-19.”
The CDC added: “Today’s update acknowledges the existence of some published reports showing limited, uncommon circumstances where people with COVID-19 infected others who were more than 6 feet away or shortly after the COVID-19- positive person left an area.” The agency said transmission took place in “poorly ventilated and enclosed spaces that often involved activities that caused heavier breathing, like singing or exercise. Such environments and activities may contribute to the buildup of virus-carrying particles.”
The agency said its recommendations for avoiding the virus remain the same.
People can protect themselves by staying at least 6 feet away from others, wearing a mask that covers their nose and mouth, washing their hands frequently, cleaning touched surfaces often and staying home when sick, the CDC said. People should also avoid crowded indoor spaces and ensure indoor spaces are properly ventilated by bringing in outdoor air as much as possible, the agency said.
EXPERTS WEIGH IN
Experts welcomed CDC’s new guidance on airborne transmission.
“There is overwhelming evidence that this is an important route of transmission for covid-19, and we have desperately needed federal guidance on this route,” said Linsey Marr, who studies aerosols at Virginia Tech and was an author of a letter in the journal Science from a group of infectious-disease physicians and aerosol experts. “I would like to emphasize that short-range airborne transmission when people are in close contact, meaning inhalation of aerosols, probably is more important than transmission by large droplets that are sprayed onto mucous membranes.”
Some of the debate around airborne transmission may stem not from substance but from terms used differently in the fields of aerosol chemistry and infectious disease. The Science letter clarifies that fluid blobs up to 100 microns wide can behave as aerosols, unlike some definitions focused on smaller particles.
“Aerosol biologists speak a slightly different language than, say, clinicians like myself do, where we’re looking more at the pragmatic application of transmission for infection control, especially in a health care environment,” Jay Butler, the CDC’s deputy director for infectious diseases, said last month. He summed up a National Academies of Sciences workshop, convened in late August to discuss the growing evidence of airborne transmission, as having “much more agreement than disagreement” around its possibility.
Covid-19 is not as contagious as measles or tuberculosis, which are primarily spread through airborne transmission and require hospitals and health care settings to treat patients in special negative-pressure infection isolation rooms to prevent spread.
WARNING FROM WHO
Dr. Michael Ryan, the head of emergencies at the WHO, said Monday that the agency’s “best estimates” indicate roughly 1 in 10 people worldwide may have been infected by the coronavirus — more than 20 times the number of confirmed cases — and warned of a difficult period ahead.
Ryan, speaking to a special session of the WHO’s 34-member executive board focusing on covid-19, said the figures vary from urban to rural areas, and among groups, but that ultimately it means “the vast majority of the world remains at risk.” He said the pandemic would continue to evolve, but that tools exist to suppress transmission and save lives.
“Many deaths have been averted and many more lives can be protected,” Ryan said. He was flanked by his boss, WHO Director- General Tedros Adhanom Ghebreyesus, who minutes earlier led a moment of silence to honor victims, as well as a round of applause for the health workers who have strove to save them.
Ryan said southeast Asia faced a surge in cases, Europe and the eastern Mediterranean were seeing an increase, while the situations in Africa and the Western Pacific were “rather more positive.” Overall, though, he said the world was “heading into a difficult period.”
“The disease continues to spread. It is on the rise in many parts of the world,” Ryan told attendees from governments that make up the executive board and provide much of the WHO’s funding. “Our current best estimates tell us that about 10% of the global population may have been infected by this virus.”
The estimate — which would amount to more than 760 million people based on a current world population of about 7.6 billion — far outstrips the number of confirmed cases as tallied by both the WHO and Johns Hopkins University, now more than 35 million worldwide. Experts have long said that the number of confirmed cases greatly undershoots the true figure.
Ryan did not elaborate on the estimate. Dr. Margaret Harris, a WHO spokeswoman, said it was based on an average of antibody studies conducted around the world. She said the estimated 90% of people remaining without infection means the virus has “opportunity” to spread further “if we don’t take action to stop it” such as by contact-tracing and tracking of cases by health officials.
MOVE ON VACCINES
Also on Monday, the White House has blocked new Food and Drug Administration guidelines on bringing potential vaccines for covid-19 to market that likely would have prevented their approval before the Nov. 3 election.
At issue was the FDA’s planned requirement that participants in the ongoing mass clinical trials for nearly a half-dozen vaccine candidates be followed for two months to ensure there are no side effects and that the vaccines provide lasting protection from the virus in order to receive emergency approval. A senior administration official confirmed the move Monday evening, saying the White House believed there was “no clinical or medical reason” to add additional screening protocols.
FDA Commissioner Stephen Hahn has pledged that career scientists, not politicians, will decide whether any coronavirus vaccine meets clearly stated standards that it works and is safe. Vaccine development usually takes years, but scientists have been racing to shorten that time.
The senior administration official, who spoke on the condition of anonymity to discuss the action, said the White House was intent on getting a safe vaccine to market and wanted to make sure “additional loopholes” weren’t added that would slow down the process.
RUSSIAN DEATH TOLL
Elsewhere in the world, Russia’s Federal Statistics Service said 45,663 people have died with covid-19 in April through August, more than double the death toll released by the government’s virus-response staff.
The latest figures from the statistics agency, known as Rosstat, include deaths both directly attributed to the coronavirus and cases where it was listed as an “important condition” leading to the lethal outcome.
The government’s virus-response staff puts the total deaths at 21,475 from the start of the epidemic through Oct. 4. According to those figures, the accuracy of which has been questioned by the World Health Organization and outside experts, Russia has one of the lowest death rates in the world.
But the Rosstat figures put Russia’s performance more in line with other countries with large outbreaks. Russia has reported the fourth-largest number of cases in the world.
The British government has launched an investigation into how nearly 16,000 new coronavirus infections went unreported as a result of a technical glitch, a failing that could have given fresh impetus to an outbreak that critics say could easily get out of control.
Health Secretary Matt Hancock told lawmakers Monday that the problem related to the “automated transfer of files.” The problem is widely thought to be connected to the file size limitations on Excel spreadsheets used in the test-and-trace program.
Hancock’s appearance at the House of Commons came after the weekend disclosure that 15,841 virus cases weren’t tabulated from Sept. 25 to Oct. 2. Though those testing positive had been told of their status, their contacts — potentially around 50,000 people — weren’t traced, a failing that could have allowed the virus to flourish.