Editor’s note: This report has been updated to correct the number of dog bite injuries as a share of pediatric ER visits over several months in 2020.

The pandemic seems to have triggered an uptick in dog bites, some of them disfiguring, a few of them fatal.

Multiple studies point to a rise in U.S. emergency room visits for canine bites since the start of COVID-19. Britain, too, has seen a surge in dog bites, an upward trend that began before the pandemic and may continue beyond it.

Researchers and dog experts can only guess at the reasons. One likely factor is the wave of pandemic pet adoptions, which put dogs in millions of homes that hadn’t had them before. Another is COVID lockdowns, which put humans and dogs in close quarters for months on end. A third is viral pet videos, encouraging human-dog staring contests and closeups of dogs “smiling” with bared fangs, episodes that don’t always end well.

Accounts of canine aggression have even emanated from the White House. Commander, a presidential German shepherd, is said to have bitten Secret Service officers. Another Biden family dog, Major, was evicted from 1600 Pennsylvania Ave. after a spate of similar incidents.

Dogs are also turning on other dogs. Dogfights aren’t new, but a recent dog-on-dog attack on Manhattan’s Upper East Side made the A section of The New York Times. A German shepherd named Syko reportedly mauled a toy poodle outside a French bookstore.

Dog bites are not a well-worn pathway of academic research. Data and reports appear sporadically, sometimes prompted by an outbreak of attacks.

One 1959 study of dog bites in Pittsburgh grouped nearly 1,000 victims into illuminating occupational categories. The toll included 414 schoolchildren, 50 housewives, 33 newspaper boys, 26 mailmen, 12 milkmen and six veterinarians.

The latest round of scholarly interest seems to have commenced with anecdotal reports of dog-bite victims arriving in emergency rooms in greater numbers.

One study, published last summer in the Journal of Craniofacial Surgery, found that dog bite injuries nearly tripled as a share of pediatric ER visits over several months in 2020, to about 8 cases for every 1,000 patients.

The surge in bites is “likely to be associated with stay-at-home orders, bringing dogs and children together for longer periods of time and perhaps in closer quarters,” the researchers wrote. “It is alarming to note that the spike of incidence of dog bites has peaked, yet persisted, even as states continue to slowly relax social restrictions.”

A second paper, published in August 2022 in the Journal of Surgical Research, found a 25 percent increase in pediatric dog bites from 2019 to 2020.

Both studies focused on children, who tend to suffer more grievous wounds in dog attacks because they are closer to the ground.

“Some of the injuries we saw were horrific,” said E.J. Caterson, chief of plastic surgery at Nemours Children’s Health in Wilmington, Del., and co-author of the second study. “These are preventable injuries, in most cases.”

Neither study looked beyond 2020. But research by DogsBite.org, a public education website, found 81 fatal dog attacks in 2021, the most recorded in any recent year by the Centers for Disease Control and Prevention.

Many dog attack fatalities are grown women in households with three or more dogs, said Colleen Lynn, founder of DogsBite.org.           

“The risk of injury really increases, the more dogs in a household,” she said.

In Britain, scholars have tracked an ongoing rise in dog attacks that may not have reached its peak.

At least four Britons have died in dog attacks this year, according to a June report in The Guardian, and 10 people died in 2022. Those are big numbers in a region that averages about three dog attack deaths a year. 

London police seized 479 animals last year under a Dangerous Dogs Act, compared to 336 in 2019.

The pandemic pet boom provides, at best, a partial explanation for the rise in violent outbursts by dogs.

Dog and cat adoptions actually declined in 2020 in the United States, shelter data show. Overall pet ownership rose, but not by much: 70 percent of American households owned pets in 2021, up from 67 percent in pre-pandemic 2019, according to a national survey by the American Pet Products Association.

Some pandemic dogs went to humans who were unschooled in how to raise them. Others suffered disruptions in their daily routines as their humans pivoted from offices to virtual work and back again.

“Dogs that have less stable personalities, that are less resilient, thrive in more predictable environments,” said Pamela Reid, vice president of the behavioral sciences team at the American Society for the Prevention of Cruelty to Animals. If a dog’s daily schedule “changed during the pandemic, and then changed back to what it was before, that could be disruptive.”

Other societal shifts may explain increased dog aggression.

One theory holds that online marketing has spurred a rise in unscrupulous breeders, who sell dogs that weren’t properly socialized as puppies.

Another potential culprit is social media. YouTubers and TikTokkers can reap millions of clicks for videos of staring contests with dogs. Trainers say that’s a no-no; staring at dogs makes them uneasy. Viral videos of dogs “smiling” are similarly unwise.

“That’s a stress smile,” said Carley Faughn, an animal behaviorist at Best Friends Animal Society. A stress smile bespeaks unease and could lead to a bite.

Dogs may be lashing out because of the heat. New research from Harvard Medical School and Spaulding Rehabilitation Hospital shows dogs are more likely to bite on hot days, and we have had a lot of those lately.

Clas Linnman, an assistant professor of physical medicine and rehabilitation and study co-author, theorizes that both dogs and humans may show more aggression at higher temperatures.

“There are lab studies indicating that rats are more aggressive when exposed to heat stress, so I think it is shared across species,” he said.

Here, then, are some tips on preventing dog bites:

Understand dog body language. An aggressive dog may try to look bigger, ears forward, fur puffed out, tail straight or even wagging. Bared teeth and growling are more obvious signs.

An anxious dog may try to look smaller, shrinking to the ground, lowering its head, licking its lips, flattening ears back, even yawning.

“Not all dogs that are uncomfortable become aggressive,” Reid said, “but dogs that become aggressive are generally uncomfortable.”

Ask before you pet an unfamiliar dog. Let it sniff your closed hand first. Avoid the top of the head.

Avoid dogs — obviously — who are barking or growling. If an unknown dog approaches and looks tense, stay quiet and still, head down.

Don’t leave a small child alone with a dog. Instruct children never to tease dogs, pull their tails or ears or mess with their toys, treats or food. Consider pet gates to separate dogs and tots.

Don’t force your dog to interact with people, especially if the dog seems reluctant. Remove the dog from any situation that resonates tension.

If someone asks to pet your dog, don’t be afraid to say no.

“What I always say is, it’s up to us,” Faughn said. “We’re teaching dogs to live in a human world.”

–Updated at 7:10 a.m.