The bacterial illness can cause swelling, pain, and joint damage, and is resistant to some antibiotics.

Credit: Daniel Hernanz Ramos/Getty Images

By now you've probably seen the nerve-racking video of a young girl who was pulled into the water by a sea lion near Vancouver, British Columbia. ABC News reports that the six-year-old is receiving preventative treatment for an infection known as seal finger. Because she suffered a small wound during the attack, experts say the illness is an unlikely but potentially dangerous possibility.

The dramatic encounter with the marine mammal became a viral sensation earlier this week. In the footage, the girl sits on the edge of a dock as others toss food to a sea lion swimming in the harbor. The animal rises out of the water and grabs the girl’s dress in its mouth, yanking her underwater. Her grandfather jumped in and lifted her to safety, her dad later told CBC News.

While the girl and her grandfather are both safe, her dad said she did suffer a wound, about two inches by four inches, and that she was prescribed antibiotics after the incident.

The family reached out to the Vancouver Aquarium, ABC News reported yesterday, after seeing aquarium staff members mention the possibility of a seal finger infection in media interviews over the weekend. “She did get a superficial wound, and she's going to get the right treatment," aquarium spokeswoman Deana Lancaster told ABC News.

According to a 2009 case report in the Canadian Journal of Plastic Surgery, seal finger infections are caused by Mycoplasma bacteria that live in the mouths of sea mammals. If the bacteria enter a person’s bloodstream—through a cut on the hand, usually—it can cause pain, swelling, and joint stiffness within one to two weeks of exposure.

Seal finger was a common infection for Norwegian and Canadian seal fishermen in the first half of the 20th century, the case report states, but it has also been documented in animal researchers, veterinarians, scuba divers, and biologists. Most commonly, the bacteria is transmitted through a bite from a marine mammal, or by handling seal pelts or seal meat. (The case described in the paper involved a Canadian man whose hand became massively swollen and stiff after hunting and skinning seals.)

Lancaster told ABC News that the infection can be debilitating, and that it can be resistant to some medications: The bacteria are extremely tiny and do not have a cell wall, which is the primary target for first-line antibiotics like penicillin. Other antibiotics, like tetracycline, are more effective.

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Before treatment with tetracycline was available, however, the infection frequently led to the loss of hand function, or of fingers themselves. “It was not uncommon that a patient at sea on a fishing voyage would demand amputation of a finger to avoid losing valuable working time and wages,” the authors of the case report wrote.

But even in modern times, they wrote, there have been numerous reports of patients being misdiagnosed and treated incorrectly—probably because many primary-care physicians have never heard of seal finger. This can result in the need for more medications, a longer recovery time, unnecessary invasive procedures, and permanent joint damage.

Luckily, doctors caring for this particular patient are aware of the potential risk of infection. Meanwhile, dock officials are taking precautions to make sure no one else gets hurt: After the incident went viral, CBC News reports, additional signs were posted, warning people not to feed the sea lions.