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Four more human cases of the Highly Pathogenic Avian Influenza (HPAI) A(H5) have been confirmed in the United States, the US Centers for Disease Control and Prevention (CDC) has stated.
All cases have been reported from Colorado, among workers who came in contact with poultry infected with HPAI H5N1 while culling them. The four cases include the earlier three presumptive-positive cases that were reported on July 12.
The CDC is also aware of an additional fifth case from the same area and will confirm it after a sample is collected. The workers complained of mild illness, conjunctivitis and eye tearing, commonly reported in earlier cases. Fever, coughing, sore throat or runny nose and chills are other symptoms of bird flu.
“Specimens forwarded to CDC for additional testing were positive for influenza A(H5). The state was then notified of the results. The designation of the influenza virus neuraminidase (the N in the subtype) is pending genetic sequencing at CDC,” a statement from the public health agency said.
The reported infections are significant as they are the first cases of H5 virus infection among poultry workers, as against the previous cases which were reported in five dairy workers.
So far, five persons from three states have been infected from dairy cattle since 2022. Four of these cases have been reported in 2024 itself.
Bird flu has spread across the US in recent weeks, with 151 dairy cattle herds and 99,095,946 poultry affected according to the CDC. The outbreaks in dairy cows and poultry have been reported as 13 and 48 respectively.
The latest outbreak in dairy cows has been reported by the Oklahoma Department of Agriculture, Food and Forestry, making it the 13th state to report an avian flu outbreak. The sample was collected from in April and sent to the USDA Animal and Plant Health Inspection Service (APHIS) for testing.
Studies show the avian flu virus is spreading among cattle due to contaminated milking equipment.
Researchers have, however, confirmed that pasteurised milk from infected cows is safe to consume.
The risk to public health from the virus continues to be low, the CDC has affirmed. However, scientists do not rule out the possibility of it causing a pandemic.
Scott Hensley, an immunologist at the University of Pennsylvania in Philadelphia, stated in an article published in the journal Nature that the virus in its existing state does not show signs of causing a pandemic.
“But with influenza viruses, that equation could entirely change with a single mutation,” Hensley said. The reason is that the virus poses the risk to evolve and infect mammals more effectively, possibly through the respiratory systems, making it more difficult to contain.
Moreover, increasing contact and airborne transmission could also trigger a pandemic.
Meanwhile, on June 26, Australia confirmed that a new strain of avian influenza had entered the country. According to the World Organisation for Animal Health, the strain detected is H7N8, reported in non-poultry birds and found 13 susceptible birds. Of these, eight were confined and five were depopulated.