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At the least one individual in Texas has been recognized with chicken flu following contact with dairy cows presumed to be contaminated, state officials said on Monday.
The announcement provides a worrying dimension to an outbreak that has affected tens of millions of birds and sea mammals worldwide and, most just lately, cows in the US.
Thus far, there aren’t any indicators that the virus has developed in ways in which would assist it unfold extra simply amongst folks, federal officers have mentioned.
The affected person’s major symptom was conjunctivitis; the person is being handled with an antiviral drug and is recovering, in line with the Facilities for Illness Management and Prevention.
The Division of Agriculture introduced the first cases in dairy herds in Texas and Kansas final week, after which, a few days later, in a further herd in Michigan. Preliminary testing means that cows in New Mexico and Idaho can also be contaminated.
The virus has been recognized as the identical model of H5N1, an influenza subtype, that’s circulating in North American birds.
The C.D.C. is working with state well being departments to watch others who could have been involved with contaminated birds and animals, the company mentioned on Monday.
That is solely the second case of H5N1 chicken flu in folks in the US; the first was in 2022. Specialists mentioned that they imagine the danger to most people stays low. However testing and evaluation is ongoing, and there are lots of unanswered questions.
“It is a quickly evolving state of affairs,” the usD.A. mentioned in its announcement final week.
Right here’s what to know:
What’s chicken flu?
Hen flu, or avian influenza, is a bunch of flu viruses which are primarily tailored to birds. The actual virus in these new circumstances, known as H5N1, was first recognized in 1996 in geese in China, and in folks in Hong Kong in 1997.
In 2020, a brand new, extremely pathogenic type of H5N1 emerged in Europe and unfold rapidly around the globe. In the US, it has affected more than 82 million farmed birds, the worst chicken flu outbreak in U.S. historical past.
For the reason that virus was first recognized, there have additionally been sporadic circumstances in folks in different nations. In 2023, there have been 248 cases of people contaminated with H5N1 virus, and 139 deaths, in line with the World Well being Group. However a overwhelming majority resulted from extended, direct contact with birds.
H5N1 doesn’t but appear to have tailored to unfold effectively amongst folks, consultants say.
How did cows get chicken flu?
Cows weren’t considered a species at excessive threat.
“The truth that they’re vulnerable — the virus can replicate, could make them sick — that’s one thing I wouldn’t have predicted,” mentioned Richard Webby, an influenza virologist at St. Jude Kids’s Analysis Hospital.
However earlier this 12 months, reviews of sick cows started rising in Texas and New Mexico. Useless birds have been additionally discovered on a few of these farms, and laboratory testing ultimately confirmed the cows have been contaminated with chicken flu.
There are a number of ways in which the virus may need discovered its manner into cattle. The probably route, a number of consultants mentioned, is that contaminated wild birds, which shed the virus of their feces and oral secretions, contaminated the cows’ meals or water.
However different free-ranging animals identified to be vulnerable to the virus, reminiscent of cats and raccoons, may even have introduced the virus onto dairy farms.
How have cows been affected?
Though the virus is commonly deadly in birds, it seems to be inflicting comparatively gentle sickness in cows.
“It’s not killing animals, and so they appear to be recovering,” mentioned Dr. Joe Armstrong, a veterinarian and cattle manufacturing knowledgeable on the College of Minnesota Extension. Final week, the usD.A. mentioned that there were no plans to “depopulate,” or kill, affected herds, which is the usual process when poultry flocks are contaminated with the virus.
The illness is primarily affecting older cows, which have developed signs that embody a lack of urge for food, a low-grade fever and a big drop in milk manufacturing. The milk that the cows do produce is commonly “thick and discolored,” according to Texas officials. The virus has additionally been present in unpasteurized milk samples collected from sick cows.
It’s not but clear whether or not the chicken flu virus is the only reason behind the entire signs and sicknesses which were reported, consultants cautioned.
How widespread is the issue?
It’s unclear. As of final Friday, the usD.A.’s Nationwide Veterinary Providers Laboratory had confirmed chicken flu infections in two herds in Texas, two herds in Kansas and one herd in Michigan. Preliminary testing has urged that extra herds in Texas, New Mexico and Idaho can also have the virus, however these findings haven’t but been confirmed by the nationwide laboratory. Thus far, it has been discovered solely in dairy cows and never in beef cattle.
However as a result of cows should not routinely examined for chicken flu, and the sickness has been comparatively gentle, there may very well be different contaminated herds which have escaped detection, consultants mentioned.
And the motion of cattle between states may transport the virus to new places. The affected dairy in Michigan had just lately imported cows from one of many contaminated Texas herds. On the time the cows have been transported, the animals weren’t displaying any signs. The farm in Idaho had additionally just lately imported cows from an affected state, Idaho officials said.
How is it spreading?
That could be a key, and nonetheless unanswered, query. It’s doable that the contaminated cows are all selecting up the virus independently, particularly if shared meals or water sources have been contaminated.
A extra worrisome chance, nonetheless, is that the virus is spreading from cow to cow. On Friday, the usD.A. famous that “transmission between cattle can’t be dominated out.”
A number of scientists mentioned that they might be stunned if there was not a point of cow-to-cow transmission. “How else may it transfer so quickly?” mentioned Dr. Gregory Grey, an infectious illness epidemiologist on the College of Texas Medical Department.
If the virus seems to unfold simply between cows, that would result in bigger, extra sustained outbreaks. It might additionally give the virus extra alternatives to adapt to its new mammalian hosts, growing the danger that it acquires mutations that make it extra harmful to folks.
How will officers know if chicken flu adapts to unfold between folks?
Analyzing the genetic sequence of the virus from contaminated birds, cows and other people can reveal whether or not H5N1 has acquired mutations that assist it unfold amongst folks.
Scientists have been intently monitoring infections in birds and sea mammals and, now, cows. Thus far, the virus doesn’t appear to have gained the power to unfold effectively between folks.
In 2012, scientists confirmed that H5N1 was in a position to spread through air between ferrets — a well-liked mannequin for finding out transmission of respiratory viruses amongst folks — after buying 5 mutations.
A pattern of chicken flu isolated from a Chilean man final 12 months had two mutations that point out adaptation to infecting mammals. However these mutations have beforehand been seen with out the virus evolving additional to unfold between folks, consultants mentioned.
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