Four more pet cats die from bird flu - raising fears a spillover could be closer

Four more pet cats have died from H5N1 bird flu in the US.

Two of the pets in South Dakota had no links to cattle dairy products - the first time there have been cases in pets without connections to outbreaks on farms.

The development could be significant because it suggests the virus is edging closer to humans.

South Dakota's state veterinarian, Beth Thompson, said there was no livestock on the property where the pets died, but said it is not yet known how to cats became infected.

Two other cases of bird flu in barn cats on commercial diary farms, where cows were also infected with H5N1, recently occurred in Michigan - one in Isabella County and another in Ionia County, where two Virginia opossums were also infected.

It is the first time there have been cases in pets without connections to cows infected to H5N1

The above map shows the states that have reported bird flu infections in dairy herds

Only one person so far - a farmer in Texas - has tested positive for H5N1 virus this outbreak, but the CDC fears many more could be infected and not coming forward.

It comes as the FDA's top official revealed the agency is gearing up for a bird flu pandemic in people that could kill one in four of those it infects.

The two cats without connections to poultry or dairy cows are from South Dakota's Campbell County, which is in the northern part of the state on the border with North Dakota.

The news came from a notification from US government officials to the World Organization for Animal Health (WOAH).

The update did not mention what symptoms the cats had, but common signs of bird flu in cats include loss of appetite, severe depression, fever, difficulty breathing and jaundice.

Previous reports of H5N1 in cats, in both America and abroad, have listed respiratory and neurologic symptoms in infected animals, which were frequently fatal. 

Earlier this month, roughly 70 Americans in Colorado were being monitored for bird flu due to potential exposure.

Up until this week, all the cats who died of bird flu had been living on farms and likely drank raw milk, which can harbor viruses because it has not been pasteurized - a process where milk is heated and then quickly cooled to kill microbes.

But the source of the two domestic cats in South Dakota is unknown, which suggests it could be spreading among them.

'Cats are particularly susceptible to H5N1 2.3.4.4b viruses and the majority of sick cats have been reported at or near affected poultry facilities or dairies,' Shilo Weir, a spokesperson for USDA’s Animal and Plant Health Inspection Service, told BNO News.

At least 14 cats have died from bird flu since the virus was found in dairy cows in late March, though the actual count is thought to be much higher because of limited testing.

The spread of H5N1 clade 2.3.4.4b across the world, as well as the spread to a growing number of mammals, has increased anxieties about the possibility of transmission between humans from a future variant.

At this point, only a few human cases have been found after contact with infected birds or cattle.

People who have close and lengthy contact with infected animals may become infected when the virus enters through their eyes or mouth, or when droplets are breathed in through the nose. 

As the virus spreads, particularly between two different species, it acquires more mutations which may allow it to infect people more easily. 

So far, there have been a total of 51 outbreaks at dairy farms in nine states.