Up early Tuesday with her 14-month-old baby, Salomé Cerqueira heard a noise and went to her front window, where she saw something that would make anyone shudder in these contagious times.

A man was criss-crossing the street, going from one recycling bin to the next, spitting on their handles, she said.

“I thought he was scavenging but no, I watched him do it again and again,” she said. “I thought, I bet he’s been doing this the whole way up the block.”

The mother of two, who is at home with both children since daycares and schools closed, immediately posted a note to her neighbourhood Facebook group.

“I don’t normally post much, but I was really concerned. I had to do it,” she said.

Then, worried that some of her neighbours near Yonge St. and St. Clair Ave. might not be on Facebook, she sent out her older son to knock on doors and warn people in person.

What Cerqueira saw might be an isolated and extreme case of wanton disregard for the health of others, but her story is not unique. Social media abounds with anecdotes of people spitting on the sidewalk, in the subway and even on elevator buttons.

At a time when the risk of contracting the COVID-19 virus from a few cough droplets has brought the world to a halt, spitting is now far worse than a social faux pas: it could be an extraordinary threat to public health.

“Generally, viruses die when they dry up and get too cold, so they might survive longer in spit because it’s wetter,” said Jennifer Palmer, a professor and co-director of the Health in Humanitarian Crises Centre at the London School of Hygiene and Tropical Medicine. “But every virus is different.”

Because COVID-19 is so new, it’s still not well understood. But unlike typical flu viruses, the coronavirus is impervious to snow and freezing temperatures, according to the World Health Organization, meaning an infected wad of spit would — at least theoretically —— leave a lasting risk of infection on outdoor surfaces, even in March in Toronto.

The major factor would be how sick the spitter is, said Kelly Grindrod, a professor in the University of Waterloo’s school of pharmacy. If they have a high viral load, their saliva could contain an enormous amount of virus, which would then live and remain contagious on a surface for hours, even days.

“If you think about those plastic bins, spitting on them is gross. But worse, it could stay on a plastic surface like that for up to three days,” she said.

With fewer person-to-person interactions due to borders closing, businesses shuttering and all public gatherings being called off, surfaces might end up being one of the most dangerous transmission vectors for COVID-19.

“Both coughing and spitting are dangerous,” said Linda Vrbova, a Toronto epidemiologist, “but coughing tends to be more so because it’s at a level where others are more likely to catch it.

“Of course, if you end up touching spit, this could be dangerous too, especially since this virus seems to be pretty hardy,” she said.

New research about the virus is emerging daily and several studies appear to have some information that would apply to spit. Researchers at the U.S. National Institutes of Health, for example, found that the coronavirus lasts longest on plastic and stainless steel surfaces, where it can survive up to 72 hours.

An epidemiological tracing study published in the Lancet found that a Chinese couple in Singapore transmitted the virus to others at a church even though they did not attend the same service. Closed circuit television footage revealed that they sat at the same spot on a pew several hours apart, meaning the virus must have survived on the seat between services.

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While washing your hands is still the number one way to prevent infection, Toronto Public Health says you can dilute bleach with water to disinfect surfaces in and around your house.

Grindrod says wiping your door knobs would be a good idea, not only to protect yourself but also others, like the mail carrier — or the garbage collector.

“I might be inclined to give those bins a wipe down before putting them out and again before bringing them back in,” she said.