United States: A new study details that a variant of avian influenza has infected birds and dairy cows across the US, leading to mammal-to-mammal transmissions, such as between cows and from cows to cats and a raccoon.
More about the study
According to Diego Diel, an associate professor of virology in the Department of Population Medicine and Diagnostic Sciences and director of the Virology Laboratory at the Animal Health Diagnostic Center (AHDC) in the College of Veterinary Medicine, “This is one of the first times that we are seeing evidence of efficient and sustained mammalian-to-mammalian transmission of highly pathogenic avian influenza H5N1,” as phys.org reported.
Whole genome sequencing of the virus did not identify any mutations in the virus that would improve the transmissibility of H5N1 in humans, although the data clearly indicates mammal-to-mammal transmission, a scenario that is possibly alarming as the virus may further mutate in mammals, Diel said.
So far, 11 human cases have been reported in the US, with the first dating back to April 2022, each with mild symptoms: four were associated with a cattle farm, and seven have been associated with a poultry farm, of which four cases were reported in the past few weeks in Colorado.
The virus identified in these recent patients was the same as that currently circulating in dairy cows used in the present research; hence, the scholars inferred that the virus may have emanated from dairy farms in the same county.
Virus ability to mutate and infect humans
The virus’s ability to infect and replicate in people is present; however, the efficiency of those infections is generally low.
According to Diel, “The concern is that potential mutations could arise that could lead to adaptation to mammals, spillover into humans, and potential efficient transmission in humans in the future.”
This means that it is necessary to continue observing the virus in infected animals and any other human beings who might be infected, Diel added.
The programs have been funded by the US Department of Agriculture, thus meaning that producers did not incur any cost for testing for H5N1.
Diel said more initial tests, stricter biosecurity measures, and possible quarantines in case of positive outcomes would be needed to curb the further spread of the virus, as phys.org reported.
Cases of H5N1 virus in the US
The H5N1 was first identified in January 2022 and has been life-threatening to more than 100 million domestic birds and thousands of wildlife in the US.
Scientists in the Cornell AHDC and the Texas A&M Veterinary Medical Diagnostic Laboratory were among the first to alert the presence of the virus in dairy cattle herds.
They probably contracted the disease from wild birds. They developed dangerous clinical signs, such as reduced feed intake in the cows, alteration in the feces, breathing difficulties, and abnormally reduced milk yields.
This research proves that the virus has a high tropism for the mammary gland and high virulent paths in infected animals’ milk. Pasteurization kills the tuberculosis virus, ensuring a safe milk supply.
Genome sequencing of characterized viral strains, modeling, and epidemiological information showed that when the infected cows from Texas were moved to a farm consisting of healthy cows in Ohio, it caused cow-to-cow transmission, as phys.org reported.
Sequencing also revealed that the virus was carried to cats, a raccoon, and wild birds, which tested positive for death from the affected farms.
Cats and raccoons may have contracted the disease by consuming raw milk from an infected cow. The researchers think the wild birds could have been infected through environmental contamination, such as aerosols stirred around during milking or cleaning the milking parlors.