A 63-year-old German man showed up at a hospital with a burning sensation in his left leg and muscle pain in both. His flulike symptoms were severe, with labored breathing for three days. Round, purplish spots on his skin looked like rashes. They were the result of capillaries bleeding just under the surface.

The patient’s heartbeat was stable, researchers said, even though he was running a temperature of 102. His labored breathing caused an inadequate supply of oxygen to his tissue. His failing kidneys were not producing urine, researchers wrote.

But for days, doctors had no idea what was wrong with him. He had not recently been in the hospital. They suspected some kind of bacteria, but he had no open wounds and did not have meningitis.

It wasn’t until his fourth day in the hospital that a blood test revealed that the man had a type of bacteria found in the saliva of healthy dogs and cats. It is usually transmitted to humans only if they are bitten.

Doctors soon realized the man was ill because his dog licked him, and that lick ultimately led to his death.

A recent medical case study published in the European Journal of Case Reports in Internal Medicine details how an otherwise healthy man died within weeks of being infected with bacteria in his dog’s saliva.

The case report does not indicate the date of the patient’s illness, nor does it say what kind of dog the man owned. But infections caused by Capnocytophaga canimorsus — bacteria found in dog, cat and even human saliva — are well-documented, though rare.

According to the Centers for Disease Control and Prevention, an infection of C. canimorsus can grow under the right conditions, though it is usually brought on by a dog bite, not a lick. It also does not typically take hold in a patient who does not already have a weakened immune system, the CDC notes.

If a serious infection does develop, it has a 30 percent mortality rate, according to the CDC, and death can be swift; a serious infection of C. canimorsus can kill a patient within 72 hours after symptom onset, the CDC says.

Researchers who studied the German man’s case also noted that C. canimorsus infections are rare with a range of symptoms. Most patients who have had severe or fatal infections from the bacteria have had immune, spleen or alcohol abuse issues, they wrote. But this particular patient did not indicate those ailments in his medical history.

Researchers said they chose to use the man’s case in a study because it was so baffling.

“Very rarely, severe C. canimorsus infections without biting or scratching have been reported,” they wrote. But only one of those cases was in a patient who did not have some kind of immunodeficiency.

Last year, a Wisconsin man lost his legs, hands and nose after contracting the same bacteria from a dog’s saliva without being bitten. He’s walking again with prosthetics, Fox 6 reported.

In July, an Ohio woman underwent partial amputations of both arms and legs while in a coma that was caused by C. canimorsus, Fox 8 Cleveland reported. In a different case study titled “Lick of death,” a 70-year-old woman was sickened by C. canimorsus after her dog licked her. She recovered.

Researchers on the case study warn that dog and cat owners who experience flulike symptoms should quickly seek medical care if their symptoms seem extreme for a typical illness. If you have been bitten by a dog or cat, the CDC suggests washing the area immediately with soap and water and contacting your doctor. Even if you don’t feel sick, someone who has been bitten by an animal still has a risk of contracting rabies, in addition to C. canimorsus.

In the German patient, doctors found multiple serious ailments: severe kidney injury, signs of liver dysfunction and rhabdomyolysis, a deterioration of muscle tissue that can result in kidney failure. He also had a buildup of lactic acid in his bloodstream. Once he was transferred to an intensive care unit, he was diagnosed as having severe sepsis with skin death and blood clotting, or purpura fulminans, according to doctors.

He was treated with antibiotics, but his health rapidly declined. The infection wrecked his body, doctors said. He went into cardiac arrest and was resuscitated, according to the paper, but he was then placed on a breathing machine.

Toward the end of his life, all of his extremities had gangrene, and a CT scan showed that he had severe brain swelling with a lack of oxygen, according to the paper.

The man’s relatives decided to reduce his treatment. He died after 16 days of care, according to doctors.

Read more: