No less than one individual in Texas has been identified with hen flu after having contact with dairy cows presumed to be contaminated, state officers mentioned on Monday.
The announcement provides a worrying dimension to an outbreak that has affected hundreds of thousands of birds and sea mammals worldwide and, most lately, cows in the US.
Up to now, there aren’t any indicators that the virus has developed in ways in which would assist it unfold extra simply amongst individuals, federal officers have mentioned.
The affected person labored straight with sick dairy cows, mentioned Lara M. Anton, a spokeswoman for the Texas Division of State Well being Companies. “We now have examined round a dozen symptomatic individuals who work at dairies, and solely the one individual has examined constructive” for the virus, she mentioned in an e-mail.
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 primary instances in dairy herds in Texas and Kansas final week, and a number of days later, in a further herd in Michigan. Preliminary testing means that cows in New Mexico and Idaho may additionally 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 different individuals who might have been involved with contaminated birds and animals, the company mentioned on Monday. It additionally urged individuals to keep away from publicity to sick or lifeless birds and animals, and to uncooked milk, feces or different doubtlessly contaminated supplies.
That is solely the second case of H5N1 hen flu in individuals in the US; the first was in 2022. The danger to most of the people stays low, specialists mentioned. However testing and evaluation is ongoing, and there are lots of unanswered questions.
“It is a quickly evolving scenario,” the usD.A. mentioned in its announcement final week.
Right here’s what to know:
What’s hen flu?
Hen flu, or avian influenza, is a bunch of flu viruses which might be primarily tailored to birds. The actual virus in these new instances, known as H5N1, was first recognized in 1996 in geese in China, and in individuals in Hong Kong in 1997.
In 2020, a brand new, extremely pathogenic type of H5N1 emerged in Europe and unfold shortly all over the world. In the US, it has affected greater than 82 million farmed birds, the worst hen flu outbreak in U.S. historical past.
Because the virus was first recognized, sporadic instances have been present in individuals in different international locations. However a overwhelming majority resulted from extended, direct contact with birds.
H5N1 doesn’t but appear to have tailored to unfold effectively amongst individuals, specialists say.
How did cows get hen flu?
Cows weren’t considered a species at excessive threat.
“The truth that they’re prone — 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 Youngsters’s Analysis Hospital.
However this yr, reviews of sick cows started to emerge in Texas and New Mexico. Lifeless birds had been additionally discovered on a few of these farms, and laboratory testing confirmed that some cows had been contaminated with hen flu.
There are a number of ways in which the virus might need discovered its approach into cattle. The seemingly route, a number of specialists mentioned, is that contaminated wild birds, which shed the virus of their feces, saliva and different secretions, contaminated the cows’ meals or water.
However different free-ranging animals recognized to be prone to the virus, resembling cats and raccoons, might even have introduced the virus onto dairy farms.
How have cows been affected?
Though the virus is usually deadly in birds, it seems to be inflicting comparatively delicate sickness in cows.
“It’s not killing animals, and so they appear to be recovering,” mentioned Dr. Joe Armstrong, a veterinarian and cattle manufacturing professional on the College of Minnesota Extension. Final week, the usD.A. mentioned 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 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 usually “thick and discolored,” in line with Texas officers. The virus has additionally been present in unpasteurized milk samples collected from sick cows.
It isn’t but clear whether or not the hen flu virus is the only real explanation for all of the signs and sicknesses which were reported, specialists cautioned.
How widespread is the issue?
It’s unclear. As of final Friday, the usD.A.’s Nationwide Veterinary Companies Laboratory had confirmed hen flu infections in two herds in Texas, two herds in Kansas and one herd in Michigan.
Preliminary testing has advised that further herds in Texas, New Mexico and Idaho may additionally have the virus, however these findings haven’t but been confirmed by the nationwide laboratory. Up to now, the virus has been discovered solely in dairy cows and never in beef cattle.
However as a result of cows should not routinely examined for hen flu, and the sickness has been comparatively delicate, there might be different contaminated herds which have escaped detection, specialists mentioned.
And the motion of cattle between states might transport the virus to new places. The affected dairy in Michigan had lately imported cows from an contaminated herd in Texas. When the cows had been transported, the animals weren’t displaying any signs. The farm in Idaho had additionally lately imported cows from an affected state, Idaho officers mentioned.
How is it spreading?
That may be a key, and nonetheless unanswered, query. It’s attainable that the contaminated cows are choosing 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 weren’t some extent of cow-to-cow transmission. “How else might it transfer so quickly?” mentioned Dr. Gregory Grey, an infectious illness epidemiologist on the College of Texas Medical Department.
If the virus can unfold simply between cows, that might result in bigger, extra sustained outbreaks. It might 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 individuals.
How will officers know if hen flu adapts to unfold between individuals?
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 individuals.
Scientists have been intently monitoring infections in birds and sea mammals and, now, cows. Up to now, the virus doesn’t appear to have the power to unfold effectively between individuals.
In 2012, scientists confirmed that H5N1 was capable of unfold by way of air between ferrets — a well-liked mannequin for finding out transmission of respiratory viruses amongst individuals — after buying 5 mutations.
A pattern of hen flu remoted from a Chilean man final yr 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 individuals, specialists mentioned.
Is it secure to eat dairy merchandise?
Federal officers have confused that commercially processed milk stays secure to drink. Dairies are required to maintain milk from sick animals out of the human meals provide, and milk offered throughout state strains should be pasteurized, a course of wherein the milk is heated to kill potential pathogens. Pasteurization “has regularly confirmed to inactivate micro organism and viruses, like influenza, in milk,” the Meals and Drug Administration mentioned in a new on-line information to exploit security.
Dr. Gail Hansen, a veterinary public well being professional and unbiased guide, agreed that the chance of being contaminated by pasteurized milk was most likely “very low.” She added, “I might not need individuals to cease consuming milk due to it.”
However the chance couldn’t be fully dominated out, she mentioned, expressing some concern that federal officers had been “overconfident within the face of so many unknowns.” If cows are shedding virus into their milk earlier than they present indicators of sickness, that milk might doubtlessly discover its approach into the industrial milk provide, she mentioned. And totally different pathogens might require totally different pasteurization temperatures and durations; the particular circumstances required to inactivate this specific virus remained unclear, Dr. Hansen mentioned.
The danger of being contaminated by the virus by consuming unpasteurized, or uncooked, dairy merchandise stays unknown, the F.D.A. mentioned. Uncooked milk is thought to pose quite a lot of potential illness dangers past avian influenza.
