The US Department of Agriculture reported two more cases of highly pathogenic avian flu in wild birds on Tuesday, raising risks for potential infections in poultry.
The USDA on Friday reported the nation’s first case of a Eurasian H5 type of the virus since 2016 and on Tuesday said all three cases are the H5N1 strain.
That strain has caused a wave of outbreaks of bird flu in poultry across Europe and Asia.
H5N1 is one of the few bird flu strains that has passed to humans, though US officials said there was a low risk to people from the case confirmed on Friday.
The infections are disappointing because it is rare for a Eurasian strain to make its way to North America, said Carol Cardona, a professor of avian health at the University of Minnesota.
“Avian influenza viruses tend to stay in their hemisphere,”she said.
The latest US cases were in Colleton County in South Carolina, where Friday’s infection was found in a wild duck, and in Hyde County in North Carolina, the USDA said.
Wild birds can transmit avian flu to each other or to poultry through direct contact and through their feathers or feces.
“These findings are not unexpected, as wild birds can be infected with HPAI and show no signs of illness,” the USDA said.
“They can carry the disease to new areas when migrating.”
The USDA advised poultry producers to review safety measures to assure the health of their flocks and said people should wear gloves when dealing with wild birds. Cardona said poultry producers need to make sure the virus cannot enter their barns.
“Poultry producers are going to be busy this spring,” she said. “They have to check the doors and windows every day, twice a day, 10 times a day.”
The World Organisation for Animal Health (OIE) said on Tuesday that Spain reported an outbreak of H5N1 bird flu on a farm north of Madrid.