Case report supports evidence of H5N1 avian influenza transmitted from cows to Texas dairy workers

Scientists at the Texas Centers for Disease Control and Prevention (CDC) and their collaborators today shared new details regarding an investigation into recently reported H5N1 avian influenza infections among dairy farm workers. This is likely the first known transmission of the virus between mammals and humans. .

The research team today announced clinical and genetic sequencing results. New England Medical Journal.The man's infection was mild conjunctivitis, which was first reported as April 1stand the CDC shared its contents Initial sequencing results the next day.

Lack of access hinders follow-up clinical research

Conjunctivitis in the man's right eye began in late March. Although he had no contact with sick or dead birds or other animals, he had direct contact with healthy dairy cows and with cows that showed signs of illness similar to cows at a nearby facility where H5N1 was confirmed. Although he wore gloves while working, he said he did not wear respiratory or eye protection.

Researchers said the man's eyes may have been infected by touching them with hands contaminated with the virus or by being exposed to droplets or aerosols from sick cows or dairy farm activities. .

Medical workers collected nasopharyngeal and conjunctival swabs, which were found to be H5N1 positive through PCR testing. There was enough RNA in the conjunctival samples to sequence the entire genome, and scientists were able to grow the virus from both specimens.

The patient also developed redness in his left eye. He and his family contacts received oseltamivir, and over the next few days, the man recovered and no symptoms were reported by his contacts.

In a supplementary appendix, the researchers said they were unable to follow up on sick farm workers or other exposures of workers. They also noted that follow-up specimens could not be collected from patients to track viral load or duration of shedding. “We were also unable to collect acute or convalescent sera to assess seroconversion in dairy workers or household contacts,” the researchers wrote.

This was announced by a spokesperson for the Texas Department of State Health Services. CBS News The Texas dairy worker said he came to a Texas field office for testing but did not give the name of his workplace.

Gaps in data, but strong evidence for cow-to-human transmission

Initial sequencing revealed that the virus belonged to the same B3.13 genotype circulating in dairy cows, and isolation of the virus from both specimens yielded identical virus. As previously reported by the CDC, the virus in this man's specimen contained a change, PB2 E67K, that is known to be associated with virus adaptation to mammalian hosts.

In a supplementary appendix, the group compares sequences from patients with available bovine sequences and finds that, while closer to bovine than B3.13, human sequences fall just outside a larger cluster of bovine sequences in Texas. He said he discovered something. Genotype viruses from wild birds or wild mammals.

“Sequence data from farms where infected dairy workers were likely exposed were not available,” the researchers said, adding that there are gaps in previous sequencing images and that the virus has been undetectable for some time. He pointed out that this suggests that the virus may have been circulating without being detected.

They said the patient may have been previously infected with a slightly different virus, or there may have been multiple independent spillovers of the B3.13 genotype from wild birds to cattle.

But taken together, they write, the genetic and epidemiological evidence provides strong evidence of transmission from diseased cattle to humans.