Q&A: What is the risk for surface, aerosol spread of COVID-19?

Months into the COVID-19 pandemic, people still question what precautions they should take to prevent the spread of the novel coronavirus on surfaces.

A recent study showed that SARS-CoV-2 can survive on certain surfaces — such as stainless steel and money — for 28 days after exposure. Additionally, there is evidence that suggests aerosol spread of COVID-19 may be possible, according to the CDC.

Early on in the pandemic, many people reported taking precautions such as wiping down their groceries and takeout food containers, with some news outlets even hosting segments and posting stories to show the public the best way to do so.

Healio Primary Care spoke with Donald W. Schaffner, PhD, distinguished professor and extension specialist in food science at Rutgers University, to learn more about the risk for surface and aerosol transmission of COVID-19, as well as what precautions people should take and which ones may be unnecessary.

Q: What should primary care physicians tell patients about their risk for becoming infected by SARS-CoV-2 on surfaces? Should they still be taking precautions like wiping down groceries?

A: I have thought from the earliest days that risk from surfaces is quite low. No evidence has emerged to convince me otherwise.

Your biggest risk from grocery shopping comes from being in the store and being around other people. The way you manage that risk is wearing a mask, visiting grocery stores that insist that everyone else wear a mask too, and staying away from people as much as possible in the store.

If you've got some hand sanitizer in your car, you can use some before getting on the road to head home.

Once you get home from the grocery store and put your groceries away, wash your hands or use hand sanitizer.

Q: What should PCPs tell patients about the risk for aerosol transmission of COVID-19?

A: I believe the scientific evidence still indicates that the greatest risk comes from droplet transmission. Droplets do not spread far — 6 feet at most, hence the 6-feet recommendation from CDC.

That said, there is evidence that the virus may also be spread by aerosols, which are smaller than droplets, do not settle to the ground as quickly, and can spread further. It appears that aerosol transmission may have been responsible for some of the large outbreaks that occurred during choir practice events, for example.

The possibility of aerosol transmission does not negate the advice to stay 6 feet away from other people, and if you can't, everybody should be wearing a mask.

Q: Many bars and restaurants have reopened indoor dining spaces heading into the winter. What should PCPs tell patients about eating in these spaces and any potential risks for transmission?

A: We know that indoor spaces appear to be riskier than outdoor spaces. We also know that situations where people are not wearing masks are higher risk. Both of these things can occur in bars and restaurants. I think the bars may be especially risky because it's not as easy to keep 6 feet of distance as we would in a restaurant, where people are seated at tables.

Personally, I'm not planning to go to a bar anytime soon, and I limit my restaurant food consumption to strictly takeout. This is the same advice I'm giving to my elderly (80+) patients.

Of course, people are free to make their own choices given the restrictions imposed by governors of their states.

Q: What precautions should PCPs tell patients to take in their homes?

A: If there is no one in the home who is sick with COVID-19 or flu-like symptoms, normal home cleanliness practices would still apply. If someone in the home is diagnosed with COVID-19, or is showing COVID-19 symptoms, I recommend following the CDC guidance.

I think it's also important to note that if no one is sick, it’s important not to overdo it when it comes to cleaning and disinfection. There was a report earlier this year that indicated that calls to poison control centers for people exposed to cleaners and disinfectants were in some cases almost double reports in a typical year.

References:

Chang A, et al. MMWR Morb Mortal Wkly Rep. 2020;doi:10.15585/mmwr.mm6916e1.

CNN. How to properly wipe down your groceries. https://www.cnn.com/videos/health/2020/04/03/sanjay-gupta-wiping-cleaning-groceries-demo-town-hall-vpx.cnn. Accessed October 28, 2020.

Fox News. Coronavirus pandemic: Doctor applies 'sterile technique' to cleaning groceries, handling takeout. https://www.foxnews.com/food-drink/coronavirus-doctor-sterile-technique-groceries-takeout. Accessed October 28, 2020.

Gharpure R, et al. MMWR Morb Mortal Wkly Rep. 2020;doi:10.15585/mmwr.mm6923e2.