trick or treat

Scientists reveal the biggest mistake you can make this Halloween

Here's how to have a sanitary spook season.

Ashley Sandberg / EyeEm/ Getty Images

In 2020, every holiday heralds new fears.

The casual summer road trip comes with considerations about quarantine. Family gatherings require complicated risk-benefit calculations, especially if older relatives are involved. And this October, Halloween offers its own conundrum.

What do you do if trick-or-treaters turn up at your door?

First, some good news: Trick-or-treating is likely not the riskiest aspect of Halloween, explains Amesh Adalja, a senior scholar at the Johns Hopkins University Center for Health Security. Rather, the dreaded coronavirus Fall surge will be driven by small indoor gatherings, according to Robert Redfield, the director of the Centers for Disease Control and Prevention (CDC).

"I think that those types of small gatherings where people haven't mixed before are going to be the challenge" Adalja tells Inverse.

But Halloween trick-or-treating does still carry risk. There are two kinds of risk: surface-based transmission (doling out of candy to strangers) and people congregating on a doorstep.

Surface-based transmission risk is low, but there are ways to reduce it even more. Oliver Kramm / EyeEm/Getty Images

Should you hand out candy? –  The odds of surface-based Covid-19 transmission (also called fomite transmission) are far lower than those of other ways the virus spreads. Far riskier are activities involving prolonged, non-masked, face-to-face interactions, or encountering small aerosols when someone talks, coughs, sneezes, or sings.

In the few cases where fomite-based transmission of the virus might occur (like inside the household), there are so many other factors at play it is difficult to pin transmission down in that way, a September review paper on Covid-19 transmission notes. Importantly, the CDC has not yet documented any case of Covid-19 that has stemmed from food packaging.

But that's not to say that the virus can't survive on surfaces.

A widely read study in the New England Journal of Medicine suggested the virus survives for up to 72 hours on plastic and stainless steel, but for less than 24 hours on cardboard. More recently, a study published in the journal Virology reports the virus may survive for as long as 28 days on glass, stainless steel, or bank notes. It fared worse on porous surfaces like cotton, however — lasting at longest, 14 days.

As grim as these findings appear, they come with a large, important caveat. The studies don't mimic real life — in fact, they barely get close to the real-world conditions we encounter the coronavirus in. The latter experiment, for example, drew criticism because it calculated virus survival in an environment that was not only totally dark (the virus is vulnerable to UV light), but also temperature and climate-controlled at 64 degrees Fahrenheit and 50 percent humidity.

Here's how the science boils down for you and your candy: JoLynn Montgomery, founder risk-assessment firm Epistudies and adjunct assistant research scientist at the University of Michigan tells Inverse there is no activity that carries zero chance of Covid-19 transmission. But handing out candy — as long as it's in a wrapper and no one has coughed or sneezed on it — is at the low end of the spectrum of risk.

The virus' ability to live on surfaces for any length of time is just one reason why that may be the case, Montgomery explains. To get sick from touching something, virus molecules first have to fall on a surface, be encountered by another person before they are no longer viable, and then make it inside the body.

"So, all of those things have to happen before the infection occurs," she says. "It doesn't just seep through your skin."

Trick-or-treating is a fleeting interaction, but you can reduce risk even more by leaving candy outside in a socially distanced way. Javier Zayas Photography/Getty Images

Studies suggest the novel coronavirus can survive on skin for up to 9 hours in controlled lab conditions. Again, the lab is not the real world. And hand washing dramatically reduces the risk, Adalja says.

There are certain instances when a surface poses higher risk, like if someone has recently coughed or sneezed directly on to it. But in most cases, dry, wrapped candy isn't an issue.

"If you have a candy that is dry, and I'm talking about candy in the wrapper, the fomite risk is very low," Montgomery says.

That said, if you feel symptomatic, test positive for Covid-19, or have been exposed to the virus, skip the activities all together.

Should you open your door? – Surface-based transmission is only one way a virus can spread. In the case of Covid-19, early studies suggest close social contact with other people is a major risk, no touching necessary. Rather, the aerosol droplets produced when a person talks, sneezes, coughs or sings may be enough to infect those around them. That's why social distancing and wearing masks are cited as important infection-control strategies.

Montgomery says she's not opening her door to trick-or-treaters this year. She's too concerned about coronavirus cases circulating in her area.

"My county is in the low levels of yellow," she says. "We have about 12 and a half cases per hundred thousand people right now, and that's higher than I'm comfortable with," she says.

When deciding whether you will open your door to trick-or-treaters, you might want to consider your locality's positive test rate, too.

The Johns Hopkins Coronavirus resource center indicates there are 33 states where the coronavirus positivity rate is higher that 5 percent — a level thought to indicate a surge in cases and a sign of hospitalizations to come.

States with higher than recommended positivity rates in yellow. Johns Hopkins Coronavirus Resource Center

Some localities are placing restrictions on trick-or-treaters. Rhode Island has banned trick-or-treating after dark, and Beverly Hills, California has banned the practice entirely. (Beverly Hills has also banned spraying shaving cream on others.)

For the person doling out candy on a doorstep, Adalja says that risk remains low. That's because passing out candy is a "fleeting" interaction — meaning it doesn't result in a significant amount of exposure. Spending a prolonged time, about 10-15 minutes or more, within six feet and without masks with another person is a concern, however. So cut the conversation short.

"Nobody is usually sticking around that long for candy at a door," Adalja notes. "But for those who have are very risk-averse then the solution is to leave the candy out."

Should you choose leave candy outside, you can go further to protect others, Montgomery says. The greatest risks stem from people congregating in crowds, which could happen on high-traffic trick-or-treating streets.

The solution she proposes: If you are going to leave out candy, don't force people to congregate around a candy bowl. Her neighbor took this to a new level by creating a socially distanced candy scavenger hunt in the park, she says. Another option would be spacing out candy packages at the end of a driveway.

"Be creative," she says. "Do it differently, we can still have fun for Halloween."

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