At least one individual in Texas has been identified with chook flu after having contact with dairy cows presumed to be contaminated, state officers stated 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 within the United States.
So 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 stated.
The affected person’s main symptom was conjunctivitis; the person is being handled with an antiviral drug and is recovering, in accordance with the Centers for Disease Control and Prevention.
The Department of Agriculture introduced the primary instances in dairy herds in Texas and Kansas final week, and some days later, in an extra herd in Michigan. Preliminary testing means that cows in New Mexico and Idaho might 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 stated on Monday.
This is just the second case of H5N1 chook flu in folks within the United States; the primary was in 2022. The threat to most people stays low, consultants stated. But testing and evaluation is ongoing, and there are numerous unanswered questions.
“This is a rapidly evolving situation,” the usD.A. stated in its announcement final week.
Here’s what to know:
What is chook flu?
Bird flu, or avian influenza, is a gaggle of flu viruses which can be primarily tailored to birds. The specific virus in these new instances, 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 United States, it has affected greater than 82 million farmed birds, the worst chook flu outbreak in U.S. historical past.
Since the virus was first recognized, sporadic instances have been present in folks in different international locations. But 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 chook flu?
Cows weren’t regarded as a species at excessive threat.
“The fact that they are susceptible — the virus can replicate, can make them sick — that is something I wouldn’t have predicted,” stated Richard Webby, an influenza virologist at St. Jude Children’s Research Hospital.
But this yr, studies of sick cows started to emerge in Texas and New Mexico. Dead birds have been additionally discovered on a few of these farms, and laboratory testing confirmed that some cows have been contaminated with chook flu.
There are a wide range of ways in which the virus might need discovered its method into cattle. The seemingly route, a number of consultants stated, is that contaminated wild birds, which shed the virus of their feces, saliva and different secretions, contaminated the cows’ meals or water.
But different free-ranging animals identified to be vulnerable to the virus, comparable to cats and raccoons, may even have introduced the virus onto dairy farms.
How have cows been affected?
Although the virus is usually deadly in birds, it seems to be inflicting comparatively delicate sickness in cows.
“It’s not killing animals, and they seem to be recovering,” stated Dr. Joe Armstrong, a veterinarian and cattle manufacturing skilled on the University of Minnesota Extension. Last week, the usD.A. stated that there have been 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 embrace a lack of urge for food, a low-grade fever and a major drop in milk manufacturing. The milk that the cows do produce is usually “thick and discolored,” in accordance with Texas officers. The virus has additionally been present in unpasteurized milk samples collected from sick cows.
It shouldn’t be but clear whether or not the chook flu virus is the only reason behind all of the signs and sicknesses which have been reported, consultants cautioned.
How widespread is the issue?
It’s unclear. As of final Friday, the usD.A.’s National Veterinary Services Laboratory had confirmed chook flu infections in two herds in Texas, two herds in Kansas and one herd in Michigan.
Initial testing has urged that extra herds in Texas, New Mexico and Idaho might also have the virus, however these findings haven’t but been confirmed by the nationwide laboratory. So far, the virus has been discovered solely in dairy cows and never in beef cattle.
But as a result of cows will not be routinely examined for chook flu, and the sickness has been comparatively delicate, there may very well be different contaminated herds which have escaped detection, consultants stated.
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 an contaminated herd in Texas. When 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 officers stated.
How is it spreading?
That is a key, and nonetheless unanswered, query. It is feasible that the contaminated cows are selecting up the virus independently, particularly if shared meals or water sources have been contaminated.
A extra worrisome risk, nonetheless, is that the virus is spreading from cow to cow. On Friday, the usD.A. famous that “transmission between cattle cannot be ruled out.”
Several scientists stated that they’d be stunned if there weren’t some extent of cow-to-cow transmission. “How else could it move so rapidly?” stated Dr. Gregory Gray, an infectious illness epidemiologist on the University of Texas Medical Branch.
If the virus can unfold simply between cows, that might result in bigger, extra sustained outbreaks. It would additionally give the virus extra alternatives to adapt to its new mammalian hosts, growing the chance that it acquires mutations that make it extra harmful to folks.
How will officers know if chook flu adapts to unfold between folks?
Analyzing the genetic sequence of the virus from contaminated birds, cows and folks 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. So far, the virus doesn’t appear to have the power to unfold effectively between folks.
In 2012, scientists confirmed that H5N1 was in a position to unfold by means of air between ferrets — a preferred mannequin for learning transmission of respiratory viruses amongst folks — after buying 5 mutations.
A pattern of chook flu remoted from a Chilean man final yr had two mutations that point out adaptation to infecting mammals. But these mutations have beforehand been seen with out the virus evolving additional to unfold between folks, consultants stated.
