Reports that a cat contracted bird flu and has not fallen ill could mean the virus is adapting to mammals and poses a potentially higher risk to humans, a World Health Organization (WHO) official said on Tuesday.
Michael Perdue, a scientist with the WHO’s global influenza program, said more studies were needed on infections in cats, including how they shed the virus.
But Perdue said there was no current evidence that cats were hidden carriers of a virus which can wipe out poultry flocks in the space of 48 hours and occasionally infects people.
Austria said on Monday that a cat in an animal sanctuary in the southern city of Graz had tested positive for the H5N1 bird flu virus but had yet to show any symptoms of the disease.
However, the virus can take up to a week to strike and perhaps the cat in Austria could still develop clinical signs, according to Perdue.
“We have to follow-up with laboratory studies to see if it (the virus) changed genetically and is not causing clinical signs,” Perdue told Reuters.
“If it is true, it would imply the virus has changed significantly,” he said.
The virus has killed 95 people in East Asia and the Middle East since late 2003. Most of the victims contracted the disease directly from sick poultry, but experts fear the virus could mutate and spread easily among people, sparking a pandemic which could kill millions.
Animals carrying H5N1 without showing any signs of ill health could make it harder to detect and contain bird flu. The longer the virus remains dormant in a mammal, without it getting sick or dying, the greater the risk of it also mutating into a more dangerous form.
“The longer it stays in mammals one would assume it is more likely to be adapted to mammals, as opposed to staying in birds. If the virus obtains all the mutations needed to transmit easily between mammals it could imply higher risk to humans,” Perdue said.
The Austrian cat was among 170 kept in cages next to birds including a swan that died of the disease and chicken and ducks found to have the virus after they were culled last month.
The Austrian authorities began testing animals at the sanctuary for H5N1 after the outbreak there.
Germany last week reported the first European case of H5N1 bird flu in a domestic cat on the northern island of Ruegen, an area where several wild birds have died from the virus.
“There is still not any indication of cat to human transmission. That would change everything, or if the virus started circulating among cats it would be problematic,” Perdue said.
If the virus circulated amongst cats, it could prove to be a “nightmare surveillance-wise,” he added.