Battle Rages Inside Hospitals Over How COVID Strikes and Kills: Aerosols or Droplets
Lambert here: This piece appeared after the CDC had removed its draft on aerosols from its website, but before the final version, reinstating aerosols, was published. That doesn’t affect the content of the piece. Readers know my views on this topic, so there’s no need to repeat them. However, I would b very interested to hear from any hospital workers in the readership on how their workplace is handling the issue.
By Robert Lewis and Christina Jewett of Kaiser Health News. Originally published at Kaiser Health News.
Front-line health care workers are locked in a heated dispute with many infection control specialists and hospital administrators over how the novel coronavirus is spread ― and therefore, what level of protective gear is appropriate.
At issue is the degree to which the virus is airborne ― capable of spreading through tiny aerosol particles lingering in the air ― or primarily transmitted through large, faster-falling droplets from, say, a sneeze or cough. This wonky, seemingly semantic debate has a real-world impact on what sort of protective measures health care companies need to take to protect their patients and workers.
The Centers for Disease Control and Prevention injected confusion into the debate Friday with guidance putting new emphasis on airborne transmission and saying the tiny aerosol particles, as well as larger droplets, are the “main way the virus spreads.” By Monday that language was gone from its website, and the agency explained that it had posted a “draft version of proposed changes” in error and that experts were still working on updating “recommendations regarding airborne transmission.” [Guidance supporting aerosol and droplet transmission were subsequently published by CDC. –lambert]
Dr. Anthony Fauci, the top U.S. infectious disease expert, addressed the debate head-on in a Sept. 10 webcast for the Harvard Medical School, pointing to scientists specializing in aerosols who argued the CDC had “really gotten it wrong over many, many years.”
“Bottom line is, there’s much more aerosol [transmission] than we thought,” Fauci said.
The topic has been deeply divisive within hospitals, largely because the question of whether an illness spreads by droplets or aerosols drives two different sets of protective practices, touching on everything from airflow within hospital wards to patient isolation to choices of protective gear. Enhanced protections would be expensive and disruptive to a number of industries, but particularly to hospitals, which have fought to keep lower-level “droplet” protections in place.
The hospital administrators and epidemiologists who argue that the virus is mostly droplet-spread cite studies that show it spreads to a small number of people, like a cold or flu. Therefore, N95 respirators and strict patient isolation practices aren’t necessary for routine care of COVID-19 patients, those officials say.
On the other side are many occupational safety experts, aerosol scientists, front-line health care workers and their unions, who are quick to note that the novel coronavirus is far deadlier than the flu ― and argue that the science suggests that high-quality, and costlier, N95 respirators should be required for routine COVID-19 patient care.
The highly protective respirators have been in short supply nationwide and have soared in price, from about $1 to $7 each. Meanwhile, research has shown high rates of asymptomatic virus transmission, putting N95s in high demand among front-line health care workers in virtually every setting.
The debate has come to a head at hospitals from coast to coast, as studies have emerged showing that live virus hangs in COVID-19 patients’ hospital rooms even in the absence of “aerosol-generating” procedures (such as intubations or breathing treatments) and has contributed to outbreaks at a nursing home, shuttle bus and choir practice.
KHN and The Guardian U.S. are examining more than 1,200 health care worker deaths from COVID-19, including many in which their family or colleagues reported they worked with inadequate personal protective gear.
Yet some front-line workers and managers disagree about exactly how and why health care workers are getting sick.
The hospital infection-control and epidemiology leaders cite studies suggesting that many health care workers are contracting the virus outside of work and at rates that mirror what’s happening in their communities.
A group of Penn Medicine epidemiologists in late July characterized research on aerosol transmission as unconvincing and cited “extensive published evidence from across the globe” showing the “overwhelming majority” of coronavirus spread is “via large respiratory droplets.”
Unions, occupational health researchers and aerosol scientists, though, reference another pile of studies showing health care workers have been hit far harder than average people ― and a study that showed active viral particles can drift in the air up to 15 feet from a patient in a hospital room. Such particles can hang in the air for up to three hours.
Backing their concerns, a July 6 letter signed by 239 scientists urged the medical community and World Health Organization to recognize “the potential for airborne spread of Covid-19.”
The letter pointed to studies that say talking, exhaling and coughing emit tiny particles that remain suspended in the air far longer than droplets and “pose a risk of exposure.”
In one ward of a Dutch nursing home with recirculated air, researchers found that 81% of the residents were diagnosed with COVID-19. Half of the workers on the ward ― who all wore surgical masks during patient care but not during breaks ― also tested positive for the virus.
Although researchers couldn’t exclude transmission by another method, the “near-simultaneous detection” of the virus among nearly all the residents pointed to aerosol spread.
The idea that the virus is spread by either droplets or aerosols is an oversimplification, said Dr. Shruti Gohil, associate medical director of epidemiology and infection prevention at the University of California-Irvine School of Medicine.
Gohil said it’s more of a spectrum, with the virus being transmitted by some droplets and some large aerosol particles as well.
One metric people in the hospital infection-control field focus on, though, is how many people one sick person infects. For COVID-19, research has shown that the number is about two ― similar to a cold or the flu. For an unequivocally airborne disease like measles, the number is closer to 12 to 18.
Measles is “what airborne [transmission] looks like,” Gohil said. “If this was truly a primary aerosol-transmissible disease, we’d be in a world of hurt.”
Hospital epidemiologists are also focused on the rate of household spread of the novel coronavirus. With the measles, the risk of an unvaccinated member of a household getting sick is 85%, said Dr. Rachael Lee, a hospital epidemiologist and assistant professor at the University of Alabama-Birmingham. For COVID-19, she said, the risk is closer to 10%.
Though the virus is believed to be spread more by droplets than aerosol particles, Lee said, staffers at UAB University Hospital wear an N95 respirator for an extra layer of protection and because the patients require so many breathing treatments or procedures considered “aerosol-generating.”
Such practices are not universal. At the University of Iowa’s hospital, health care workers use N95s and face shields for aerosol-generating procedures but otherwise use surgical masks and face shields for routine care of COVID patients, said Dr. Daniel Diekema, director of the division of infectious diseases at the university.
He said such “enhanced droplet precautions” are working. Places where workers are correctly using regular medical masks and face shields are finding no significant spread of the disease among staffers, although one such report focused on the spread from a single patient.
Elsewhere, patients have also been safe on floors where COVID-19 patients and those without the virus have been placed in adjacent rooms ― a practice those concerned about aerosol spread do not endorse.
“It’s not an airborne disease the way measles or tuberculosis is,” said Dr. Shira Doron, an epidemiologist at Tufts Medical Center in Boston and an assistant professor at Tufts medical school. “We know because we don’t see outbreaks that affect multiple patients on a floor.”
Origin of the Debate
The CDC helped set the stage for the current debate. In March, the agency issued revised guidance essentially saying it was “acceptable” for health care workers to use surgical masks ― instead of N95s ― for routine care. The guidance said respiratory droplets were the most likely source of transmission and recommended N95s only for aerosol-generating procedures.
“The contribution of small respirable particles, sometimes called aerosols or droplet nuclei, to close proximity transmission is currently uncertain. However, airborne transmission from person-to-person over long distances is unlikely,” according to the guidance.
The California Hospital Association sent a letter to the state’s congressional delegation urging the revised guidance be made permanent.
“We need the CDC to clearly, not conditionally, move from airborne to droplet precautions for patients and health care workers,” the letter said. Doing so would enable hospitals to preserve PPE supplies and limit the use of special isolation rooms for COVID patients.
An association spokesperson told KHN that the group wasn’t weighing in on the science, merely pressing for clarity of the rules.
Christopher Friese, professor of nursing, health management and policy at the University of Michigan, is among the experts who think those rules have endangered health care workers.
“We lost a tremendous amount of time and, candidly, lives because the early guidance was to wear N95s only for those specific procedures,” Friese said.
Family members and union leaders from Missouri to Michigan to California have raised concerns about nurses dying of COVID-19 after caring for virus patients without N95 respirators. In such cases, hospitals have said they followed CDC guidance.
Friese echoed some occupational safety experts who suggested stronger guidance from the CDC early on calling the disease airborne might have had an impact ― perhaps pressuring President Donald Trump to invoke the Defense Production Act to boost supplies of N95s so “we might have the supply we need everywhere we need,” Friese said.
Surveys across the country show there’s still a shortage of personal protective equipment at many health care facilities.
The CDC guidance posted Friday would have put pressure on some hospitals to bolster their protective measures, something they have reportedly resisted. It said the virus can spread when a person sings, talks or breathes.
“These particles can be inhaled into the nose, mouth, airways, and lungs and cause infection,” the site said. “This is thought to be the main way the virus spreads.”
By Monday morning, the website was back to saying the virus mainly spreads through droplets, noting that draft language had been posted in error.
The University of Nebraska Medical Center has been taking so-called airborne precautions from the start. There, Dr. James Lawler, a physician and director of the Global Center for Health Security at the university, said his colleagues documented that the virus can drift in the air and live on surfaces at an extensive distance from patients.
He said the hospital tests all admitted patients for the virus and keeps COVID-19 patients apart from the general population. He said they pay close attention to cleaning shared spaces and monitoring airflow within the restricted-access unit. Workers also had N95 respirators or PAPRS, which are fitted hoods with filtered air pumped in.
All of it has added up to a “very low” rate of health care worker infections.
Amid uncertainty about the virus, and as an unprecedented number of health care workers are dying, adopting the “highest possible” forms of protection seems the best course, said Betsy Marville, nurse organizer for the 1199SEIU United Healthcare Workers East union in Florida.
That would mean a departure from CDC guidelines that now say health care workers need an N95 respirator only for “aerosol-generating” procedures, like intubations or other breathing treatments. She said the rule has left the nurses she represents in Florida scrambling for protective gear ― or unprotected ― when patients need such treatments urgently.
“You don’t leave your patient in distress and go looking for a mask,” she said. “That’s crazy.”