Mysterious outbreak of bird flu in cows in the US is spreading, also infecting cats

This brings the count to eleven infected dairy farms in four states: seven in Texas, two in Kansas, one in New Mexico and one in Michigan. An employee in Texas also became infected. He got an eye infection, but is doing well.

In addition, at least three cats in Texas appear to have become infected with the virus, Texas health authorities announced. The animals had symptoms of illness, although further details have not been released. The cats may have contracted the virus by eating infected birds: dead birds were found on some farms in Texas.

‘Non-carnivores’

“Infected cats don’t surprise me that much, we have seen that before,” virologist Marion Koopmans (Erasmus MC) responds to the latest developments when asked. For example, last year at least 89 cats became infected in Poland after eating cat food contaminated with bird flu, of which 29 died. And an outbreak in South Korea infected cats in two animal shelters.

The H5N1 outbreak entered a new phase last weekend, when authorities announced the first cases in dairy cows, plus another small outbreak in goats. That is new and ‘quite special’, says Koopmans. ‘These are non-carnivores. Infections among ruminants have not previously been identified for bird flu.’

In theory, this could mean that cows have always been susceptible to bird flu, but that it has simply not been noticed before. Another possibility is that something special happened. “There may be an epidemiological explanation, such as infected birds in livestock feed,” says Koopmans. ‘The big question everyone has at the moment is: what exactly is going on there? Has anything changed about the virus?’

‘Close contact’

The American health service CDC maintains that the risk of infection in humans is low. Koopmans agrees, despite all the unrest in the US. ‘This virus does not seem to infect people very easily. For that you really have to have intensive contact with an infected animal.’

Cats are risky in that game: after all, they often come to people’s homes and sleep on their laps and in bed. Yet, as far as we know, there is no documented case of the bird flu virus jumping to humans from a cat. ‘The chance is small. But the risk is not zero,’ says Koopmans. ‘If you have an H5-infected cat and you lie down on one pillow with it, that is of course intensive contact.’

The H5N1 variant currently sweeping America is a direct descendant of a virus strain that emerged in Europe in 2020. In the US alone, the virus has killed an estimated 80 million birds. The great fear, however, is that the virus will combine with other flu viruses and thus adapt to exist in humans. There are no H5 flu viruses circulating among humans, which would make such a virus extra harmful to humans.