When 58-year-old Sharon Larson of Milwaukee, Wisconsin, got nipped by her new puppy last June, the small bite seemed pretty minor at first. Until she developed flu-like symptoms that came on quickly and only got worse.

Within two days, she was dead.

Larson tested positive for a bacterial infection called Capnocytophaga canimorsus.

That same month, another Wisconsin resident, Greg Manteufel of West Bend, developed the same bacterial infection. In his case, the infection came not from a dog bite but a dog lick. Unlike Larson, Manteufel lived. But not before doctors had to amputate his hands and lower legs to save his life.

Like Larson, 48-year-old Manteufel fell ill with flu-like symptoms that came on fast and wouldn’t respond to antibiotics. And, like Larson, he tested positive for Capnocytophaga canimorsus.

Capnocytophaga canimorsus is a species of bacteria that lives in the mouths of healthy cats and dogs. It doesn’t make them sick, and it doesn’t make most humans sick. But in a small percentage of cases, people who come in contact with the saliva of a cat or dog that contains the bacteria, usually through bites, licks, or other close contact, do fall ill.

According to the US Centers for Disease Control, the people most at risk are those with weakened immune systems (including those who have had their spleens removed), drink alcohol to excess, and have HIV or cancer. Even then, infection is rare.

But once infected, it’s a crapshoot.

Approximately 3 in 10 infected people die. Sometimes as quickly as 24 hours after the symptoms start.

Of particular concern to healthcare professionals is the fact that neither Larson nor Manteufel had any of the common risk factors.

“It’s extremely rare,” William Schaffner, MD, a professor of infectious disease at Vanderbilt University Medical Center in Nashville, Tennessee, told NBC news. “We don’t know why some people get very ill from it and some don’t. This can affect a perfectly normal person.”

Of even more concern is the fact that a third Wisconsin resident, a then-three-year-old boy named Liam Young, had his toes and fingers amputated in 2015 after developing rapid onset flu-like symptoms. There’s no recorded instance of Young coming into contact with a dog or cat prior to the onset, but a full genetic scan of the boy completed just last month revealed the presence of Capnocytophaga canimorsus. Young survived, and is doing fine today.

Although all three victims live in Wisconsin, there are no known links between any of them.

NEWStat asked Steve Holmstrom, DVM, DAVDC, if these stories were cause for concern among veterinary staff who work around cats and dogs all day, especially during dental procedures, when the risk of exposure to Capnocytophaga canimorsus through contact with saliva is greatest.

Holmstrom, a veterinary dental expert who coauthored the 2013 AAHA Dental Care Guidelines for Dogs and Cats, reassured: “I’ve never personally seen a case nor heard of a veterinary healthcare professional having [a Capnocytophaga canimorsus infection]. This bacteria is very common [but] I have not seen any association with periodontal disease.” Holmstrom adds, “Almost all dogs carry this organism and the human infection is very rare.”

Even so, what can staff do to protect themselves? “Infection is prevented by what we have been preaching for years: personal protective equipment (PPE),” Holmstrom said. “Bite avoidance, saliva avoidance, bite first aid, and general-hygiene measures are the key. In addition to PPE, this should be focus in the veterinary setting.”

For more on these and other tips, see the 2019 AAHA Dental Care Guidelines for Dogs and Cats.