Following a deadly virus from dogs to humans

New research highlights an overlooked risk of caring for infected pets

Tick bites are nasty. These relatives of spiders can carry a nasty mix of bacteria, allergens, and viruses that lead to illnesses ranging from Lyme diseaseopens in new tab/window and red meat allergy to a viral infection, which causes severe bleeding.

This infection, called severe fever with thrombocytopenia syndrome (SFTS), can begin with a high fever and diarrhea, then escalate into internal bleeding and organ failure. The potentially deadly disease is endemic in parts of East Asia, with reported fatality rates ranging from 10% to 30%. And it doesn’t just stop with one species.

In a new study, researchers traced the SFTS virus from a man back to his sick dogs, confirming that the virus can spread from dogs to humans. The findings, published in the Cell Press journal Infection, Genetics and Evolutionopens in new tab/window, revealed another route for infection beyond a tick bite and underscores the importance of safety measures when handling sick pets.

“We provide evidence for the direct dog-to-human transmission of the virus through close contact with infected pet dogs,” wrote the authors.

The case

In April 2024, a three-year-old male dog from China became sick with SFTS. He was lethargic and feverish, with diarrhea that turned bloody. The researchers found high levels of the SFTS virus in his saliva, urine, and stool. The presence of the virus in these bodily fluids suggested a potential risk of transmission to people caring for sick pets.

Two weeks after the dog became sick, his 40-year-old male owner fell ill, too. Given the timing, the researchers suspected the man had contracted SFTS from his dog. He also reported no tick bites and had cared for the sick dog without protective equipment such as gloves or a mask.

When the researchers compared samples, “genomic sequencing revealed 100% identity between the viral strains from the dog and the owner,” they noted. In other words, the infection likely passed from dog to owner.

“This study provides the first molecular confirmation of direct SFTSV transmission from dogs to humans, identifying bloody stools and saliva as high-risk transmission sources,” explained the authors.

The importance of care with caution

Scientists already know that both dogs and cats can contract SFTS, but the disease can manifest differently. Previous case studiesopens in new tab/window found that felines can also pass the virus to people and are particularly vulnerable to the infection, with a 62.5% fatality rate.

Dogs, however, pose a different challenge — they can start spreading the virus before they appear sick. Dogs are also in more frequent contact with humans during everyday care. This means owners may be cuddling, feeding, or cleaning up after an infected dog without realizing there is a risk.

The researchers highlighted the importance of taking precautions when caring for feverish animals in endemic areas, even if the animals have no known tick bites or appear only mildly ill. These areas include China, South Korea, and Japan.

“These findings underscore the importance of including dogs in SFTS [virus] surveillance systems and implementing protective measures when handling sick pets in endemic areas,” concluded the authors.