​Poland is the first country to report "high numbers" of cats infected with bird flu across a large area, the WHO said Monday, adding that the risk of human infection remained low.

​The World Health Organization said that since Polish health authorities informed it last month of unusual cat deaths across the country, 29 cats had tested positive for H5N1 bird flu.

They were among 46 cats and one captive caracal tested for the virus, it said, adding that 14 of the infected animals were reported to have been euthanised, while another 11 had died.

The last death was reported on June 30.​

"The source of the exposure of cats to the virus is currently unknown and epizootic investigations are ongoing," WHO said in a statement.

​Some cats developed severe symptoms including difficulty in breathing, bloody diarrhoea and neurological signs, with rapid deterioration and death in some cases.

​Since late 2021, Europe has had its worst-ever outbreak of bird flu, while North and South America have also experienced severe outbreaks.

​This has led to the culling of tens of millions of poultry worldwide, many with the H5N1 strain of the virus, which first emerged in 1996.

​There has recently been a worrying spike in infections in mammals.

​The UN health agency pointed out that sporadic infection of cats with H5N1 had previously been reported.

​"But this is the first report of a high numbers of infected cats over a wide geographical area within a country," it said.

​As of July 12, no human contacts of infected cats had reported symptoms, the WHO said, adding that the surveillance period for all contacts had been completed.

​It stressed that the risk of human infections following exposure to infected cats had been assessed as low for the general population in Poland.

​The risk for cat owners, veterinarians and others who might be exposed more regularly to H5N1-infected cats without using personal protective equipment was meanwhile seen as low to moderate, it said.

​Bird flu infections in humans are rare, but when they occur can cause severe disease with a high mortality rate.

​Human H5N1 cases are usually the result of direct or indirect exposure to infected live or dead poultry or contaminated environments.

​Since 2020, the WHO said it had received 12 reports of human H5N1 cases worldwide. Four of them were severe cases, while eight were mild or asymptomatic.

© Agence France-Presse