British scientists are closely monitoring the bird flu outbreak in the US after the H5N1 virus infected more than 30 cattle herds across multiple states.
One person became infected after coming into contact with cows.
Cows in the UK are not currently being tested for bird flu and Department for Environment, Food and Rural Affairs (Defra) scientists are monitoring the situation in the US.
The virus is believed to have been spreading in the United States for weeks; Tests show that one in five commercial milk samples in the US contain traces of the virus, suggesting the outbreak is more widespread than previously thought.
What’s going on in the USA?
The US Center for Disease Control (CDC) says there is an outbreak affecting 34 dairy animals in nine states.
Traces of the bird flu virus are commonly found in milk sold in the United States, but drinking pasteurized milk does not pose any risk to humans, officials said. Their research revealed that the pasteurization process successfully killed the virus, meaning it was not contagious.
US officials warned against drinking ‘raw’ (unpasteurized) milk.
One individual, a Texas farm worker, has been confirmed to have contracted bird flu and conjunctivitis (eye infection) in the current outbreak following exposure to dairy cows.
CDC said: “This is the first time these avian influenza viruses have been found in cattle. CDC has confirmed a human HPAI A(H5N1) infection in Texas exposed to dairy cattle presumed infected with the virus.”
“Although thought to be rare, exposure to HPAI A(H5N1) avian influenza virus is the first example of possible mammal-to-human transmission.”
What does this mean for the UK?
British cows are not currently tested for bird flu.
DEFRA said there was currently no evidence of the virus spreading among cattle in the UK but was monitoring the outbreak in the US closely.
It was stated that the virus was different from the H5N1 circulating in England and Europe and that the possibility of the same virus appearing in cattle in England was “extremely unlikely”.
The US warns that the introduction of the H5N1 virus into the UK is most likely through the trade in cattle products from affected farms in the US or through migratory wild birds. However, Defra said the risk of birds introducing the virus was “very low” and that live cattle were not traded, adding: “There is no evidence that this is happening [introducing of the virus to the UK] occurred based on genomic analysis of outbreaks in Great Britain.”
The USA allowed raw milk imports. While drinking pasteurized milk is not thought to pose any risk to humans, the CDC says that “individuals with close, prolonged, or unprotected exposure to unpasteurized (“raw”) milk…are at a greater risk of infection.”
According to officials, no steps have been taken by UK authorities to restrict the import of products of animal origin from the US.
Scientists at the UK Health Safety Agency and Defra also urged farmers to “be careful”.
A situation assessment published by Defra on April 25 said: “All dairy operators should remain vigilant and ensure that visitors to their premises have not had any recent contact with dairy cattle or beef facilities in the affected areas.
“People working on farms or handling animals returning from affected areas should avoid contact with domestic cattle or domestic poultry in commercial and small holdings.”
Why are people worried?
Experts worry that the virus may evolve to spread between people.
Scientists at the United Nations have called ongoing H5N1 bird flu infections a “major public health problem” but noted that no human-to-human transmission of H5N1 has yet been recorded.
Chief Scientist of the World Health Organization (WHO), Dr. Jeremy Farrar said bird flu had an ‘extremely high’ death rate in humans. H5N1 spread from poultry and ducks to animals such as dairy cows, Farrar said.
Both the CDC and UKHSA say the risk to the public remains low, but Farrar warned it was a ‘major concern’ if the virus evolved to spread from person to person.
Farrar said health authorities need to “make sure that if H5N1 spreads from person to person, we are in a position to respond immediately by providing equitable access to vaccines, treatments and diagnostics.”
Is the virus evolving?
Evolutionary biologist Dr. from the University of Arizona. Michael Worobey said the virus in the human case was significantly different from samples of bird flu virus from infected cattle that were made public by government officials last weekend.
The difference between the genetic sequences of the worker virus and the 239 other samples provided indicates that “this is a very long-standing, widespread epidemic.”
A CDC spokesperson said “there are always some subtle changes in genetic sequences when flu viruses move from host to host,” but added that data shows the virus from birds infected cows and then spread to humans.