The new coronavirus is good at finding hosts when it is airborne, especially indoors. Knowing that, could ventilation systems spread the virus around? And do we still need to worry about surfaces?

Seattle Times readers have sent in a lot of questions on this topic as people visit restaurants or go shopping, workers look at returning to offices, and some kids go back to school. In those scenarios, touching surfaces and breathing air pumped through an HVAC system is inevitable. So, we’ll take a look at both in this week’s FAQ Friday.

How likely are you to get the virus by touching a surface?

The main way the virus spreads is from person to person through the air, via droplets released when you sneeze, cough, laugh, sing, speak or even just breathe. That’s why experts recommend wearing a mask, keeping your distance and staying outdoors rather than indoors.

That said, surfaces can’t be ruled out entirely.

“It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes,” according to the U.S. Centers for Disease Control and Prevention. “This is not thought to be the main way the virus spreads, but we are still learning more about how this virus spreads.”

When the virus is on a surface, it becomes less potent over time, according to Dr. Frank Esper, an infectious disease specialist with the Cleveland Clinic.

Some surfaces are more hospitable to the virus than others, Esper said in a Cleveland Clinic article: “The virus typically doesn’t like to live on surfaces that have a lot of holes or microscopic little grooves, nooks or crannies. It likes surfaces that are very smooth, like doorknobs.”


With that in mind, it is still a good idea to wash your hands frequently for at least 20 seconds, avoid touching your face and disinfect shared surfaces.

Can the virus be spread through a building’s ventilation system?

There hasn’t been as much research on this topic as there has been about other aspects of how the coronavirus spreads. Other diseases like influenza, measles and SARS have been proven to spread through ventilation systems.

A recent paper from a group of virologists and aerosol scientists found that tiny respiratory droplets floating in the air, called aerosols, can contain live virus.

“This is what people have been clamoring for,” Linsey Marr, an expert in airborne spread of viruses who was not involved in the work, told the New York Times. “It’s unambiguous evidence that there is infectious virus in aerosols.”

This matters because aerosols can linger in the air. They don’t dissipate as easily indoors as they do outdoors. Indoor settings have proven to be more conducive to spreading the virus, as evidenced by a small birthday party in Tacoma and a church choir practice in Mount Vernon.

The World Health Organization says people should “avoid crowded places, close-contact settings, and confined and enclosed spaces with poor ventilation,” and that homes and offices should ensure good ventilation.


The possibility of airborne spread indoors has enormous implications for how people should protect themselves.

People may need to minimize time indoors with others from outside the household, in addition to maintaining a safe distance and wearing cloth face coverings. Businesses, schools and nursing homes may need to invest in new ventilation systems or ultraviolet lights that destroy the virus.

As we head into a week of potentially record-breaking temperatures, it will be tempting to head inside to places with air conditioning. But the less ventilation there is in those spaces, the more opportunity the disease has to spread, Dr. Edward Nardell, a professor of environmental health and immunology and infectious diseases at Harvard Medical School told NPR.

“It is not the air conditioner that is doing anything particularly,” he said. “It is the fact that you are indoors, you are not socially distancing and you are rebreathing the air that people have just exhaled.”

If you are the rare person in Seattle with air conditioning at home, or you’re working in a building that uses an HVAC system, it is important that it is regularly pulling fresh air from outside. And, if possible, install a HEPA filter, which can catch viruses.

Businesses and building managers scramble to address fears that coronavirus can spread through shared indoor air

You can read last week’s FAQ Friday, about how to safely host overnight guests and take a road trip with more than one other person, at If you have a question you haven’t seen addressed in The Seattle Times’ coverage, ask it at or via the form below.

Do you have questions about the coronavirus that causes COVID-19?

Ask in the form below and we’ll dig for answers. If you’re using a mobile device and can’t see the form on this page, ask your question here. If you have specific medical questions, please contact your doctor.