Genomic analysis shows occasional jumping back of virus from infected cows to birds and cats, suggesting multi-host outbreak
Photo for representation: iStock Bird flu or H5N1, a strain of the highly pathogenic avian influenza (HPAI), has been spreading among cows in the United States for almost five months, new data indicated.
A primary genomic analysis revealed that the outbreak is likely to have started in December 2023 or early January. The first case of the strain jumping from wild birds was announced on March 25, 2024. Since then, the H5N1 strain infected 34 herds in nine states of the US, according to reports.
H5N1 has infected millions of birds and animals over the years and may cause a global pandemic, health experts flagged.
Read more: ‘Wise to assume bird flu pandemic will cause more severe disease in humans than COVID-19’
The infection has been “silently spreading” among the US cattle, a report in the journal Nature showed. The undetected circulation of the virus is attributed to the lack of data about its origin and evolution, the authors noted.
Metadata such as each sample’s precise data and state from where it was sourced are not available. The missing links prevent scientists from understanding how the virus may have been transmitted between cows and herds and identify exactly when the strain first jumped to cows.
Karthik Gangavarapu, a computational biologist with Scripps Research in La Jolla, California, who processed the data on the Sequence Read Archive (SRA), told Nature that a repository managed by the US National Center for Biotechnology Information (NCBI) is said to have about 10 gigabytes of sequencing information from 239 animals. The samples are from animals such as cows, chickens and cats.
The pathogen isolated from infected cattle showed genetic diversity, implying that the virus has been evolving over months, said Martha Nelson, a genomic epidemiologist at NCBI in Bethesda, Maryland.
The scientists also found mutations in the viral-protein section, which indicates potential adaptation for spread among mammals.
Instances of the virus jumping back from infected cows to birds and cats were also noted, suggesting the possibility of a multi-host outbreak.
Earlier this month, a person with exposure to dairy cattle was reportedly infected with bird flu. But data showed that genome sequenced from infected person did not match the signature mutations observed in the cattle.
It opens up the possibility that the person was infected from an entirely different viral lineage, which has not yet been obtained from infected cattle, scientists claimed. Another possibility lies in the person directly catching infection from a wild bird, they added.
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