A patient from Louisiana has been hospitalised after he was diagnosed with a ‘severe’ case of avian influenza A (H5N1) infection.
This case marks the first instance of severe illness related to the virus reported in the United States confirmed by the Centers for Disease Control and Prevention (CDC) on December 13.
It is also the first case of infection from H5N1 avian influenza in the US linked to the exposure from a backyard flock, as the patient reportedly had been exposed to sick and dead birds in such flocks. Earlier cases detected have been linked to commercial dairy or poultry farms.
The total number of human cases infected by the virus since April this year have increased to 61, including the one from Louisiana. The other cases reported mild symptoms among patients.
On December 18, the same day when CDC issued a report on severe illness of the person, the Wisconsin Department of Health Services (DHS) reported the first presumptive positive human case of H5N1 or bird flu virus from Barron County. The test is pending confirmation from CDC.
The US health agency also said, “Partial viral genome data of the H5N1 avian influenza virus that infected the patient in Louisiana indicates that the virus belongs to the D1.1 genotype related to other D1.1 viruses recently detected in wild birds and poultry in the United States and in recent human cases in British Columbia, Canada, and Washington state.”
In November, a teenager from Canada was hospitalised following infection from (Influenza A (H5N1), clade 2.3.4.4b, genotype D1.1) which was found to have mutated to adapt better to infect humans.
The CDC said the H5N1 avian influenza virus is different from the B3.13 genotype found in dairy cows, poultry outbreaks and sporadic cases in multiple states.
Additional genomic sequencing and efforts to isolate the virus from clinical specimens from the patient in Louisiana are underway at CDC, the organisation said.
It added that such sporadic cases of H5N1 bird flu infection is not unexpected and has been linked with severe human illness in 2024 and earlier, including death.
“This case underscores that, in addition to affected commercial poultry and dairy operations, wild birds and backyard flocks also can be a source of exposure,” the CDC stated.
The instance of severe human case from the virus infection has prompted the health agency to classify it under a new category — ‘other animal exposure’.
In another development related to bird flu, Australian scientists have revealed that the clade 2.3.2.1a of highly pathogenic avian influenza A (H5N1) virus was responsible for infecting a child who travelled from India to the country.
The 2.5-year-old girl returned from Kolkata in India to Melbourne in Australia on February 29 this year.
“The child became ill in India; her family sought medical care on February 28. After returning to Australia, she was hospitalised on March 2, then transferred with severe influenza on March 4 and admitted to intensive care with respiratory failure requiring mechanical ventilation,” a study has noted.
The patient had no history of confirmed contact with raw poultry products or poultry, making it difficult to identify the source of infection.
The researchers stated that a previously unreported analysis of the virus showed that it was ‘reassortant’ (containing genetic material from two different viruses), consisting clade 2.3.2.1a, 2.3.4.4b and low pathogenicity avian influenza gene segments from wild birds.
The clade 2.3.2.1a clade is is known to be circulating in Bangladesh and the findings underline the surveillance gaps in South Asia and lack of data from India, the study said.
Previously, two human cases involving clade 2.3.2.1 were reported from Nepal and India in 2019 and 2021 respectively.
“The fatal case in New Delhi in 2021, involving an 11-year-old boy who had contact with poultry (although no infected birds were reported), is consistent with the genome reported here and genetically similar to H5N1 viruses present in Bangladesh,” the study observed.
The authors of the research concluded that the complex reassortment origins of the virus from the child show that clade 2.3.4.4.b viruses disseminated globally through wild birds might be transforming the genetic structure of other H5N1 clades endemic in poultry.