Explainer: What to know about bird flu in dairy cows and the risk to humans

CTI Logistics

03/04/2024 21:37

By Julie Steenhuysen
       CHICAGO, April 3 (Reuters) - Texas officials reported on
Monday that a farm worker tested positive for H5N1, or bird flu,
that has spread to dairy cows in Texas, Kansas, New Mexico,
Michigan and Idaho - the first time the virus has infected
cattle.
    Health officials and scientists say the risk to humans
remains low, but many questions remain.
    
    IS BIRD FLU A CONCERN?
    The Texas case is only the second time bird flu has been
confirmed in a human in the United States, with the first
occurring in 2022 in Colorado in a person exposed to infected
poultry. In both cases, the infections were mild.
    The Texas farm worker's only symptom was conjunctivitis, or
pink eye. He is being treated with Tamiflu, which is used to
treat human influenza. 
    The infections are from the same subtype of bird flu that
has been infecting wild birds and poultry flocks globally for
more than two years, also killing several mammal species that
likely contracted the virus from consuming sick or dead birds.

    WHAT ARE THE RISKS OF BIRD FLU?
    Some outbreaks of avian influenza have caused serious or
fatal infections among people who have close contact with wild
birds or poultry. Currently, H5N1 is not capable of spreading
easily among humans, but scientists have been on alert for
changes that could facilitate human spread and spark a pandemic.
    Dr. Thomas Inglesby, director of the Johns Hopkins Center
for Health Security, said the Texas case "doesn't change the
overall risk of a major pandemic," but stressed that any new
case should be investigated to ensure it is not spreading from
person to person.
    An official with the U.S. Centers for Disease Control and
Prevention (CDC) said for most people who are not exposed to
infected animals, the risk is very low.
    The CDC has analyzed the genetic sequences of the virus in
the infected cattle and the dairy worker and determined that
they lack changes that would make it better adapted to be
transmitted among mammals.

    DOES BIRD FLU AFFECT THE FOOD SUPPLY?
    The risk of contaminated milk reaching consumers is of "no
concern" according to the U.S. Department of Agriculture because
pasteurization kills viruses and milk from sick cows is not
being sold. 
    The CDC renewed its warning that people should not consume
raw milk or cheese, which can contain a number of pathogens.
    At this point, no beef cattle are known to have been
infected with the virus.
    
        IS THERE A BIRD FLU VACCINE FOR HUMANS?
    The U.S. has a stockpile of bird flu vaccines matched with 
the strain currently circulating, as well as antivirals that
could be used to treat human infections, Inglesby said. If there
were a major epidemic or a pandemic, the U.S. would have to
scale up "in a huge way," he said.
    The CDC has sample or "seed" strains of virus that
manufacturers could use to make more vaccine that closely
matches the circulating virus, an official said.
    Flu vaccine suppliers Sanofi  SASY.PA , GlaxoSmithKline
 GSK.L  and CSL Seqirus  CSL.AX  said in statements they are
monitoring avian flu and stand ready to develop avian flu
vaccines as needed.
    
        HOW WERE THE COWS INFECTED WITH H5N1?
    Richard Webby, a virologist at St. Jude's Children's
Research Hospital in Memphis, Tennessee, said it is still not
clear how the cows became infected, how many have been infected
or how the virus has spread to other herds, but said there's
"reasonable evidence that there has been some cow-to-cow
spread."

 (Reporting by Julie Steenhuysen
Editing by Caroline Humer and Bill Berkrot)
 ((julie.steenhuysen@thomsonreuters.com; 312-408-8131; Reuters
Messaging: Julie.steenhuysen.reuters.com@reuters.net))