A mysterious illness is worrying dog owners in the United States. Hundreds of animals across at least seven US states – including Colorado, Rhode Island, Oregon, New Hampshire and Massachusetts – have contracted a severe cough sometimes followed by respiratory distress. This type of canine pneumonia, very resistant to treatment, has already killed several of the affected animals, reports the Washington Post.

Veterinarians recorded the first cases in October. An unusually high number of dogs with the same symptoms flocked to practices. These generally start with a simple cough which progresses to pneumonia, before turning into severe respiratory distress.

Analytical laboratories are mobilizing to find a cure, while the disease is resistant to antibiotics. The owner of Thunder, a Hutski who died in two weeks after having a sudden cough, expressed her distress on BFMTV. “I want to testify: our dogs are getting sick,” she exclaimed in tears, declaring that she wanted to give “meaning” to the sudden death of her dog, that two weeks of treatment and a veterinary bill of more than 16,900 dollars could not save.

“We don’t know what the cause is and we can’t say with certainty how it is transmitted,” said Lindsey Ganzer, a veterinarian in Colorado, whose center has received at least 35 cases since October 20, four of which are deceased. The veterinarian describes the symptoms as fever, cough, lack of appetite, runny eyes and nose, sneezing and difficulty breathing.

Many questions remain about this strange disease, such as its mortality rate or its possible contagiousness for humans. However, scientists recommend that owners avoid contact between dogs, even though the potential pathogen has been detected in nasal and throat swabs, which dogs can transmit through play. “I would strongly recommend that people avoid boarding facilities, doggy daycares, anything that could represent a high volume of dogs in a space,” warned Lindsey Ganzer as quoted by the Washington Post.