It's happened at schools, stores and offices, warehouses and city halls: Someone who might be infected with the coronavirus passes through.
The building often closes. Then come the calming words: deep cleaning.
The idea is that a thorough cleaning and disinfecting could help prevent people from getting sick. The virus is spread mainly through person-to-person contact, though people can also catch it from droplets exhaled when an infected person coughs or sneezes. Those droplets can stick to surfaces, and the virus can survive for hours or days, according to health officials.
A deep clean is supposed to kill it.
The term sounds official, but it isn't. It has no standardized definition.
One company says the right approach is using a mechanical sprayer or thermal fogger that mists disinfectant into the air, then wiping all surfaces. Another swears by taking everything out of each room, disinfecting it all and then putting it back.
Some have warned against trusting competitors who, they say, only wipe down places that get touched a lot, like doorknobs or handles, or don't require workers to wear heavy-duty protective gear.
“Deep cleaning is really just a term they use to make the public feel warm and fuzzy,” said Erick McCallum, founder of Texas-based the Cleaning Guys, which handled ebola cleanup during a 2014 outbreak in Dallas.
Health experts say it's enough to clean frequently with soap, alcohol or bleach-based products. "You don't need any unusual procedures or cleaning agents," says Dr. Timothy Brewer, professor of medicine and epidemiology at UCLA.
That hasn't stopped the onslaught of calls for deep cleaning.
The Servpro Extreme Response Team typically handles calls related to water or fire damage repairs in California, Nevada and Arizona. Now it gets about 100 inquiries a week on coronavirus cleanings and goes on four related calls a day.
Aftermath Services, based in Illinois, generally cleans up crime scenes and biohazards. The flood of calls about coronavirus-related cleanings threatened to overwhelm it, so the company pulled people from its finance department to help answer the phones.
"It’s all hands on deck," said Casey Decker, Aftermath's vice president of field services.
The calls haven't slowed even as more companies require employees to work from home.
As restaurants, bars, gyms and other businesses close their doors, some professional cleaning firms expect demand will ramp up. Buildings can be thoroughly disinfected when there are no customers or employees inside.
“It's very possible that almost everything will end up shutting down," said Vanessa Cabrera, director of client services at All Clean Inc. MD, which cleans commercial and industrial properties on the East Coast. "When that’s the case, then we’ll have a lot more people calling and more jobs to do.... They’re going to want a deep clean of their facility.”
Workers, at times, might wear full-face respirators, one-piece protective suits, two pairs of gloves and booties, particularly if they're at a place that had confirmed cases of the coronavirus. Brewer, the UCLA professor, said booties and respirators aren't necessary. A face shield or surgical mask will do.
"When you’re going in and you’re 100% encapsulated, you feel like you can go up against anything,” Decker said of wearing a protective suit.
Cabrera's mother, Adriana Corona, a manager at All Clean Inc. MD, is often in the field with workers and said they now wear more protective gear than they would during their normal course of work. She's also done online training on how to do deep cleanings.
She said she hasn't been afraid of becoming infected while on jobs. "We just clean and disinfect everything," Corona said.
Clean Harbors, a Massachusetts company that specializes in hazardous waste removal, designates three different zones for its employees when they arrive at a decontamination job.
Workers suit up in the "warm zone" before entering the "hot zone," where decontamination occurs. After the job is done, one person who did not enter the building helps the others take off their suits back in the warm zone before they can enter the "cold zone," or clean area.
The protective gear is put into a drum and incinerated. The respirators are rinsed with bleach, soap and water before they're used again.
In some ways, there's precedent for the kind of thorough disinfection that cleaning companies are now doing. Some have compared the work to sewage and mold removal or to cleanups of crime scenes and meth labs. Some even have experience with other viruses, such as MRSA or norovirus.
“We’re used to this," said Chuck Geer, senior vice president of field services at Clean Harbors. "It’s not uncommon at any point in time for our teams to respond to something like this.”
His company, he said, helped clean up ground zero in New York after the Sept. 11, 2001, attacks; decontaminated oily boats after the Deepwater Horizon oil rig explosion in the Gulf of Mexico; and also has experience with anthrax.
In each of these cases, "you normally know exactly what you're cleaning up," Geer said. But with the coronavirus, "you can’t see it," he said. "When you go into a room or a building, you have to disinfect everything."
Art Dickerson, president of restoration firm Paul Davis Commercial, compared coronavirus cleanings to sewage or mold cleanups. Workers use the same types of disinfectants.
But these recent jobs are on "a wider scale," he said. "We only get so many mold jobs or sewage jobs a year.”
The demand for coronavirus cleanings has shifted Aftermath's primary business from crime-scene cleanups to "virucidal disinfection," a term a company official acknowledged does not roll off the tongue.
Aftermath now gets about 500 to 600 calls per day nationwide, up from its usual 50 to 75 calls. Calls have been coming in from all parts of the country, though California is a hot spot, said Vikas Chopra, director of marketing.
Prices vary depending on the size of the place to be cleaned and the types of services desired. For a 800- to 1,000-square-foot building, All Clean Inc. MD charges between $800 and $1,200. Servpro charges 50 cents to $2.50 per square foot.
But it's important not to go overboard with the cleaning.
Using antimicrobial solutions could inadvertently lead to antimicrobial resistance that can lead to super bugs, said Erica Hartmann, assistant professor of civil and environmental engineering at Northwestern University, who specializes in environmental microbiology.
“Yes, wash your hands. Yes, you can disinfect high-touch surfaces, but within reason,” she said. "We’re not aiming to sterilize everything around us.”
Times staff writer Molly Hennessy-Fiske contributed to this report.