Americans are stockpiling cleaning supplies again, even though research suggests COVID-19 does not primarily spread through surfaces. Experts say that's okay.

• Costco, Walmart, and Kroger have reported an increased demand for cleaning supplies as COVID-19 cases spike in the US.
• But the CDC updated guidelines in May to say surface transmission "isn't thought to be the main way the virus spreads," and updated research suggests COVID-19 can spread through non-ventilated air.
• Public health experts say Americans are stockpiling household supplies because it provides a feeling of control over the situation.
• Cleaning surfaces can also decrease flu cases and other illnesses, which can lead to less crowded COVID-19 testing sites.

Coronavirus cases are on the rise in the US and Americans are once again buying up cleaning supplies.

A winter surge in COVID-19 cases has led to record hospitalizations and deaths this month. Health experts warn the holiday season may be responsible for spreading the virus as families gather indoors outside of their immediate household.

Last spring, when COVID-19 cases and hospitalizations had first surged, demand for cleaning supplies skyrocketed as Americans sought to sanitize contaminated surfaces. Lysol and Clorox ramped up production to meet customer demand and urged Americans not to stockpile cleaners.

Now stores are again reporting high demand for cleaning supplies. Costco said on a Thursday earnings call demand and sales went up for three products - nitrile gloves, cleaning wipes, and cleaning sprays - due to the rise in COVID-19 cases. Walmart has struggled to keep cleaning supplies in stock, and Kroger imposed a limit on paper towel purchases last month.

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But researchers know much more about how COVID-19 spreads now than the did in March, and new data suggests surfaces don't spread the virus as much as previously thought. The CDC updated guidelines in May to say surface transmission "isn't thought to be the main way the virus spreads."

So why are Americans still mass-buying household supplies?

"We are seeing a lot of people buying up cleaning supplies and wearing gloves when they don't necessarily need to be wearing gloves, whereas we also see a lot of people not wearing masks when they really should be wearing masks," Ellie Murray, an assistant professor of epidemiology at the Boston University School of Public Health, told Business Insider. "So there's a little bit of a mis-connection between the communication that people are trying to put out and the information that Americans are receiving."

Buying cleaning supplies might not prevent you from getting COVID-19, but experts agree staying clean and healthy is still good.

When Americans stockpiled Clorox wipes and toilet paper in March, public health experts said the coronavirus spreads through touching contaminated surfaces and then touching your face and mouth.

But studies on outbreaks and contact tracing analysis have since suggested COVID-19 spreads primarily through close contact, not surfaces. A recent review of 172 studies show wearing a mask and keeping at least three feet apart from others are the best way to avoid catching coronavirus. Hundreds of scientists have asked the World Health Organization to recognize the risk of "airborne transmission" of COVID-19. Air spread is thought to be responsible for major outbreaks in a Washington choir practice and a call center in South Korea.

But the data may not be telling a complete story.

Murray said two factors make it hard to know how much the coronavirus spreads through surfaces: Americans are doing a better job of cleaning surfaces than usual, and contact tracing people you've shared air with is easier than figuring out who shared your restaurant table. It might take researchers years to fully understand how COVID-19 spreads.

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Still, there is no doubt COVID-19 spreads through the air, said Ryan Malosh, an assistant research scientist at the University of Michigan School of Public Health. The virus can also suspend in non-ventilated air for longer and travel further than six feet.

Avoiding getting COVID-19 through the air requires mask wearing not just of an individual, but of everyone around them. The reason why Americans are rushing to buy cleaning supplies could be because disinfecting surfaces offers control, Malosh said. The control may not exist if an wary individual leaves their house to get groceries in a crowd of maskless customers.

Even though cleaning surfaces might not be the best method of preventing COVID-19 transmission, sanitizing objects is still good. The virus does live on smooth, nonporous surfaces for days, so cleaning shared items and frequently washing your hands can work as a lower-priority precaution to physical distancing and mask wearing.

The newfound cleaning frenzy may be contributing to a decrease in flu cases. Fewer sick people would mean fewer crowds at testing sites, Murray said, because people will not confuse COVID-19 with other diseases.

Consequences for having too many cleaning products include the higher chance of mixing chemicals, which can create toxic gas, Murray said. But for the most part, experts say cleaning is okay.

"Even if it's not particularly effective, it feels good to do, [and] it's not harmful." Malosh said of buying cleaners. "So I don't think there's any reason for us to discourage it."