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(Repetition of the story without modification of the text) by Julie Steenhuysen
US authorities have stepped up measures to contain the spread of the first known outbreak of avian flu (H5N1) in dairy cows, which has now spread to 33 herds in eight states and contaminated the country’s milk supply.
So far, only one person — a Texas farmworker — has tested positive for H5N1, and although health officials and scientists say the risk to humans remains low, many questions remain.
WHY ARE H5N1 OR BIRD FLU OF CONCERN?
The spread of avian flu among dairy cows reflects the widening range of mammals susceptible to infection by the virus that typically infects birds.
Scientists are watching for any changes to the H5N1 virus that could indicate it is adapting to spread easily in humans. The virus has caused serious or fatal infections in people in close contact with wild birds or poultry. It has long been on the list of viruses with pandemic potential, and any expansion to a new mammal species is cause for concern.
The livestock infections are caused by the same subtype of avian flu that has been infecting wild birds and poultry worldwide for more than two years, also killing several species of mammals that likely contracted the virus by consuming birds. sick or dead.
HOW SIGNIFICANT IS THE AV IARIA INFLUENZA OUTBREAK IN LIVESTOCK?
The scale of the outbreak remains unknown, but several recent developments suggest it may affect more herds than have been documented.
On April 23, the U.S. Food and Drug Administration said it had detected H5N1 particles in milk. Tests suggest that these are remnants of viruses killed during the pasteurization process and that the milk is safe. Initial tests failed to detect any live virus in milk samples, and US health authorities believe that you cannot get sick from drinking pasteurized milk () and recommend against drinking untreated milk. pasteurized.
Authorities have learned that the virus can be present in cows that show no signs of infection, and that the milk from these cows does not show signs of infection such as thickness and yellow color.
To stem the outbreak, the U.S. government requires that dairy cows moving interstate () be tested for avian flu.
WHEN DID THE BIRD FLU OUTBREAK START?
US authorities thought the outbreak was recent, but new information suggests it may have started late last year.
After the U.S. Department of Agriculture released some raw genetic data to a public database on April 21, a team of evolutionary biologists led by Dr. Michael Worobey of the University of Arizona pieced together the genetic codes of the virus.
The team mapped the outbreak by tracking the evolution of the virus as it spread through the herds. Based on this analysis, Worobey said in an interview on April 24 that the outbreak in dairy cows occurred as a result of a single bird-to-cow transmission. at the end of 2023, probably in December.
HOW DOES H5N1 SPREAD?
It is still unclear how the virus is spread, but there is evidence of wild bird to cow transmission, cow to cow transmission, cow to poultry transmission and one case of cow to cow transmission. ‘man. There is no evidence of human-to-human transmission.
Due to the high viral load in milk and mammary glands, scientists suspect that the virus is transmitted to animals during milking, either through contact with infected equipment or through aerosolization of the virus during cleaning procedures.
It is not yet known whether the virus can spread through respiratory droplets that infect the airways, as flu viruses typically do in humans.
IS THERE A VACCINE AGAINST BIRD FLU FOR HUMAN?
The United States has a stockpile of avian flu vaccines matching the strain currently in circulation, as well as antivirals that could be used to treat human infections. In the event of a major epidemic or pandemic, the United States should considerably strengthen its system.
Flu vaccine suppliers Sanofi SASY.PA , GlaxoSmithKline GSK.L and CSL Seqirus CSL.AX said they were monitoring bird flu and standing ready.