Discussion thread: H5N1 avian flu in US dairy cows including human cases (poultry, dairy workers) - March 24, 2024 +

[sharon sanders]

hat tip Michael Coston


Virus Material Found in 38% of Retail Milk Samples at Lab Virus Material Found in 38% of Retail Milk Samples at Lab
April 24, 2024
​

snip

The Ohio State lab is part of the National Institutes of Health (NIH) network for the Centers for Excellence in Influenza Research and Response. As the team worked together to generate scientific data, Bowman and the team needed to try to get a handle on the scope of the new outbreak of HPAI H5N1 in cattle. They decided it would be quicker and more efficient to test samples of retail milk versus visiting every dairy farm in the country.

“We've tested 150 samples, 58 of those have tested positive to date,” says Bowman. “We've screened them for the presence of influenza genetic material, so the viral RNA. Those that have tested positive, we have been forwarded to St. Jude Children's Research Hospital, where they are conducting studies to see if there's a viable virus in there. To date, none of them have been viable, but certainly they give the indication that there is viral genetic material in the region.”

Bowman says the team purchased milk from six different states, and the processing plant codes on those 58 positives represent 10 different states where the milk was processed.

“I think this certainly gives us some idea that it's a larger problem than the handful of states in the 38 farms that had been reported,” says Bowman. “I think it's much more common.”

The difference between finding viral RNA, which is genetic material, versus a live virus, is a major point in reassuring consumers the U.S. milk supply is safe, but it’s also a key metric in tracking how widespread the virus actually is.

more...

https://www.bovinevetonline.com/new...ting-and-reporting-hpai-dairy-cattle-new-data

​

From:"FluTrackers" <flutrackers@earthlink.net>
To: <bowman REDACTED
Subject: From Sharon Sanders at FluTrackers.com
Date: Apr 25, 2024 10:27 AM​

Hi Dr. Bowman!

Can you verify the comments, that reportedly came from you, in this media report please?

https://www.bovinevetonline.com/new...ting-and-reporting-hpai-dairy-cattle-new-data

I will publish your response.

Thank you.

Sincerely,

Sharon Sanders
Editor-in-Chief
FluTrackers.com​

 

[Mary Wilson]

Early tests of H5N1 prevalence in milk suggest U.S. bird flu outbreak in cows is widespread

April 25, 2024
By Megan Molteni​

... The team that produced that data — the St. Jude and OSU groups — told STAT that it has so far analyzed four samples of store-bought milk which had tested positive via PCR for H5N1 genetic material. “We’ve done the viral growth assays to see if we can recover any virus from them and we can’t,” Webby said.

Those four samples came from an initial collection of 22 commercial milk products purchased in the Columbus, Ohio, area. “It was basically just me hitting up the five grocery stores between campus and my house,” said Bowman.

PCR testing at OSU revealed 33 of those 22 products to be positive for viral RNA. Bowman sent them to Webby to inject into plates of mammalian cells and embryonated chicken eggs and look for any signs of active viral replication. In order to do that, Webby needed a negative control so he went and bought milk at a store near his lab in Memphis. But PCR testing found H5N1 RNA in that sample too, making it useless as a negative control, but an additional data point showing a lack of live virus. ...

The St. Jude group is now repeating the experiment with the additional samples Bowman and his graduate student bought around the Midwest. Their early findings provide further evidence that H5N1 is spreading broadly among dairy cows in the US...

“Both of these data — the milk data and the genetic data that shows this has been around since December of last year — suggests that the outbreak is probably much bigger than we know,” said Angie Rasmussen, a virologist who studies emerging zoonotic pathogens at the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Canada....

“This is telling us that we’re probably already seeing that milk from asymptomatically infected cows does have some virus in there,” said Andrew Pekosz, a molecular microbiologist who studies respiratory viruses at Johns Hopkins Bloomberg School of Public Health. ...​

https://www.statnews.com/2024/04/25/h5n1-bird-flu-cows-outbreak-likely-widespread/?utm_campaign=rss

 

[sharon sanders]

From: FluTrackers <flutrackers@earthlink.net>
Sent: Thursday, April 25, 2024 10:24 AM
To: Webby, Richard REDACTED
Subject: From Sharon Sanders at FluTrackers.com
​

Hi Dr. Webby!

Can you verify your comments published in the below media article please?

https://www.statnews.com/2024/04/25/h5n1-bird-flu-cows-outbreak-likely-widespread/?utm_campaign=rss


I will publish your response.

Thank you.


Sincerely,

Sharon Sanders
Editor-in-Chief
FluTrackers.com
​

From:
"Webby, Richard" REDACTED
To: "FluTrackers" <flutrackers@earthlink.net>
Subject: RE: From Sharon Sanders at FluTrackers.com
Date: Apr 25, 2024 11:50 AM​

Hi Sharon,
Yep, that's accurate. We have more of Andys samples in cells now to increase our sample size. But to date we haven't see a trace of virus growth as perhaps expected (certainly hoped!).
Regards
Richard​

 

[Mary Wilson]

A Message to the Ag Industry about H5N1

​April 24, 2024
By RHONDA BROOKS​

... how the dairy industry must deal with the growing impact of H5N1, says Russo, Novonesis technical services manager for dairy and poultry. She’s watched the spread of the virus with alarm and urges U.S. leaders across dairy and agriculture to step up and take action.

“Address it head-on,” she says. “Don’t hide.”

As with all major threats, she says ag needs a comprehensive, cohesive plan to address the virus in dairy – and to also look at how to protect the beef, pork and poultry industries. ...

“We have a very clear picture that it's in the udder and is being shed in milk. But where else do we need to be concerned? That matters because that is going to define the control tactics to reduce spreading it from cow to cow. Those questions are ultimately going to be the pillar of our understanding and help to define strategies for controlling the virus in a sustainable way.”

... “The first clinical symptom I saw was cows that had indigestion. They had manure that wasn’t well-digested, manure with particles of feed in it,” she says.

As she checked more cows and talked with colleagues, more information came to light and she began to identify recurring symptoms: thick, colostrum-like milk; lesions on cow vulvas; high temperatures; respiratory distress; a drop in feed consumption; and a corresponding lack of rumination. ...

“The most surprising part of this, in my mind, is the fact that we’re finding so much virus as we are in the milk, in the mammary gland,” Magstadt ( clinical associate professor at the Iowa State Veterinary Diagnostic Laboratory) says. ...

https://www.bovinevetonline.com/news/industry/message-ag-industry-about-h5n1
​
​

 

[Mary Wilson]

UK cows not being tested for bird flu despite outbreak in US

​Thursday 25 April 2024 17:36, UK
Thomas Moore
​
Cows in the UK are not being tested for bird flu, despite the outbreak sweeping through American dairy herds, Sky News has been told.

The Department for Environment, Food and Rural Affairs (Defra) said reports of the H5N1 virus in UK birds and poultry are currently so low that it does not consider cattle to be at risk. ...

"The risk level in the UK has not changed," they said. ...

https://news.sky.com/story/uk-cows-not-being-tested-for-bird-flu-despite-outbreak-in-us-13122833

​

 

[Pathfinder]

Michael Worobey@MichaelWorobey​

A few thoughts on the role of pigs in the emergence of influenza A virus in mammals.

1. It is simply not the case that movement of flu viruses into non-swine mammal species requires pigs as a "mixing vessel".
9:56 AM · Apr 24, 2024
...
2. Here is a list of mammalian influenza A lineages that *did not* require the involvement of pigs:

Canine flu
Equine flu
Phocine flu
Now bovine flu.
I'll save you a google search: "phocine" = seals/sea lions.
...
3. Pigs are tested routinely for flu in the US and it is likely that H5N1 would have been detected by now if it was circulating in pigs (h/t
@swientist).

4. A big push to screen asymptomatic cattle, and those who work in close contact with them, is important right now.
...
5. In addition to looking for viral RNA or antigens, *much* could be learned by an extensive serological studies (looking for antibodies that show an animal or non-human animal has been infected by H5N1).
​
----------------------------------------------


Michael Worobey@MichaelWorobey

Given (1) how widespread bovine H5N1 is, (2) how long it has been circulating (~4 months we estimate), and how prevalent it appears to be (present in commercial milk supply), I predict this outbreak will leave most cattle in the US recovered and immune within a few months.

​11:42 AM · Apr 25, 2024

 

[Mary Wilson]

USDA orders H5N1 testing of some dairy cows to limit spread of bird flu

April 24, 2024
By Helen Branswell​

... USDA has met some resistance from farmers who they’ve suspected of having infected cows. Farmers have been told they must discard any milk produced by cows that are infected with H5N1 virus, though it’s not clear if or how that recommendation is being enforced. And evidence that milk containing virus has made its way into the milk supply suggests either some farmers have ignored the advice, or asymptomatic infected cows may be emit viruses in their milk.

“There has been a little bit of reluctance from some of the producers to allow us to gather information from their farms. That has been improving here more recently,” he said, suggesting the federal order should also increase USDA’s access.

“With the federal order going into place, this is going to really help us address any gaps that might exist in terms of … knowing what’s happening with the cattle,” Watson said.

Likewise, Nirav Shah, the CDC’s principal deputy director, acknowledged there has been some difficulty in investigating the health of workers on some farms where H5N1 has been detected.
​
“We’ve had a diversity of levels of engagement with farms,” Shah said. “These situations are challenging. ...

https://www.statnews.com/2024/04/24/h5n1-bird-flu-usda-orders-dairy-cow-testing/

​

 

[sharon sanders]

Someone asked me a question so I am posting my opinion/answer here. If anyone disagrees, please do. This area is our discussion area of this site:

sharon sanders Today, 03:43 PM

Hi!

Well...the beef industry is probably shaking in their boots. I have not seen anything about them testing any beef cattle for H5N1...they might be secretly doing it however...I have no idea.

Poultry is a different story....there are many, many years of global experience with H5N1 poultry. We followed Indonesia closely in the early days and apparently then and throughout the years - cooking chicken very well kills the H5N1 virus - at least the prior strains. Chickens are cheap and quick to "grow" again. This is why the US and most Western countries cull the affected flock, clean the area, and start over. Other countries vaccinate with limited success. I think the poultry industry has adapted to the new H5N1 scenario in the US. Are they testing all the time? I have no idea. I think they test when chickens start looking sick and/or dyiing.

For me - we do not eat raw eggs, raw meat, raw milk - as a regular routine due to salmonella, etc.

We are still eating chicken and beef and we are sure to cook it medium well. i.e. no red blood. We like the taste of medium well so that fits for us.

We do not drink milk but the FDA better get their act together and determine what level of heat and for how long it takes to - for sure - not guessing - kill H5N1 viral material.

This is classic H5N1 outbreak scenario and our government knows what to expect from years of planning exercises. Probably that is all getting thrown out the window from industry pressures...my guess.

I have no idea what is going to happen but wild migratory birds are not going away.

​

 

[Vibrant62]

One thing I am puzzled by. This is being continually referred to as HPAI as opposed to LPAI... high path would normally mean a switch of amino acid in the polybasic cleavage site as memory serves, which is what brings about the high path status - i.e leading to lots of deaths of the host organism. (see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5312086/). This has been the case (historically) even in ducks. We are not seeing mass die-offs of cattle here yet it is being referred to as HPAI. Now sequences are not being made publicly available (or are they? Still catching up with the background for this outbreak). Is this virus that is infecting cattle actually LPAI but is being mis-represented? The risks for human adaptation remain, but I am just puzzled here that the virus appears so benign. If it is indeed an HPAI H5N1, is there some genetic reassortment with bovine influenza that means it has lost a substantial part of its virulence? This is an important question to answer and understand.

 

[sharon sanders]

bump this

 

[Treyfish]

Avian Influenza in US cattle

Posted by: Defra Press Office,
Posted on: 26 April 2024 -
There have been media reports this week about the discovery of highly pathogenic avian influenza (H5N1) in dairy cattle in the US.

We are monitoring the situation closely but at this time have no reason to suspect the virus is circulating in our cattle, nor is this strain of the virus circulating in Europe. We have had no recent cases of avian influenza in kept birds and the risk level from wild birds is low.

We remain vigilant to any changes in risk and are continuing to use international disease monitoring programmes in the Animal and Plant Health Agency and UK Health Security Agency to monitor the situation.

A Government spokesperson said:

We are monitoring reports of highly pathogenic avian influenza (H5N1) identified in dairy cattle in the USA and are working closely with international counterparts to better understand the virus strain associated with these cases.

These reports do not change the risk level for animals for the UK, which is currently ‘low’ and we have no reason to suspect the virus is circulating in our cattle and nor is this virus strain circulating in Europe.

Food Standards Agency advice remains that avian influenza poses a very low food safety risk for UK consumers.​

​:tiphat:
​​​​​​https://deframedia.blog.gov.uk/2024/04/26/avian-influenza-in-us-cattle/

 

[Treyfish]

Start Mass Testing Dairy Workers for Bird Flu


H5N1 has spread stealthily among cows. Could it also be spreading silently in humans?

April 26, 2024 at 9:00 AM EDT
Given how devastating another global pandemic would be, the US should start mass testing of dairy workers for the bird flu virus that’s spreading fast through cows. If necessary, either the Centers for Disease Control and Prevention or the US Department of Agriculture should pay people to get tested. The USDA’s recent call to test more cows isn’t going far enough.

This week, scientists announced they’d found viral fragments in milk on supermarket shelves, with an alarming 58 of 150 samples testing positive. Scientists initially thought that milk from infected cows was always thick and discolored, but these results show it can look deceptively normal....:tiphat:

​https://www.bloomberg.com/opinion/a...le-have-bird-flu-we-won-t-know-unless-we-test

 

[Treyfish]

Bird Flu Is Starting to Spread Rapidly Among Cow Populations. FDA Sounds the Alarm.


Published

2 hours ago

on

By

Citizen Frank

...........

​​​​​​Officials and experts said the lack of clear and timely updates by some federal agencies responding to the outbreak recall similar communication missteps at the start of the coronavirus pandemic. They point, in particular, to a failure to provide more details publicly about how the H5N1 virus is spreading in cows and about the safety of the milk supply.

“This requires multiple agencies to coordinate and communicate internally, but most importantly externally, which doesn’t seem to be happening due to different cultures, priorities, legal responsibilities, scientific expertise, and agility,” said Katelyn Jetelina, an epidemiologist who writes a weekly infectious-diseases newsletter and has closely tracked the avian flu outbreak. “Mix that in with the usual challenges of scientific uncertainty, complexity and, quite frankly global pressure, and you got yourself an utterly, unacceptable mess.”
​.....“This work is an urgent priority as we work to ensure the continued effectiveness of the federal-state milk safety system and reinforce [the Food and Drug Administration’s] current assessment that the commercial milk supply is safe,” the administration official said....
Responsibility for monitoring and containing the outbreak is divided among three agencies. USDA leads the investigation into the virus in cows, the FDA oversees food safety, and the Centers for Disease Control and Prevention is monitoring risks to people.

Agencies have given individual updates on their parts of the outbreak investigation, but Wednesday marked the first time since bird flu was detected in cows four weeks ago that CDC, FDA and USDA, along with other agencies, held a news briefing jointly.
​....

​​​​​​Officials are seeking answers to other key questions: They want to know whether the virus is spreading among cows through mechanical means, such as milking equipment, as evidence suggests, or through the air, which would be more dangerous and lead to more sustained spread. They are also interested in knowing how long livestock will shed virus in their milk once they have recovered from an infection. And, crucially, they will seek to ascertain the risks for human exposure and whether protocols are in place at the state level if additional people test positive....


​.....
“Given this is a novel outbreak, testing needs to be done widely and rapidly, investigators need to be on affected farms, and scientists and policymakers need to be bringing it all together to set a coordinated plan of action,” Tom Inglesby, director of the Johns Hopkins Center for Health Security
...Michael Worobey, a University of Arizona virologist who led a team of scientists who analyzed 239 genetic sequences released Sunday by the USDA, said the evolutionary tree of the virus “resoundingly indicates that this outbreak had a single origin and that it had been circulating under our noses for months before it was noticed.”...


​....Public health and veterinary experts say they also want more epidemiological data — including information on the movement of animals, their feed sources and how many workers are on-site — to understand how and where the virus is circulating.

Beth Thompson, South Dakota’s state veterinarian and president of the National Assembly of State Animal Health Officials, said such information needs to be shared quickly.

“It’s like if you just rip one page out of a chapter in a book and hand it to the states, that isn’t the whole chapter,” Thompson said. “We need all of the information to be given back to us.”
​.....
:tiphat:
https://www.cf.org/news/bird-flu-is...y-among-cow-populations-fda-sounds-the-alarm/

 

[Treyfish]

Cattle Veterinarians Express Confusion over U.S. Response to Bird Flu


Denial and a lack of unity across states are limiting a swift response to the novel outbreak
by Rachel Nuwer
April 25, 2024
When U.S. officials first announced in late March 2024 that the H5N1 avian influenza had been detected in Texas dairy herds, Beth Thompson knew it was only a matter of time before the virus reached cows in South Dakota, where she serves as the state veterinarian. Her prediction came true days later on April 8, when she received an email reporting likely cases of H5N1 in approximately 50 cows at a dairy in an unidentified part of the state.

​...."This is not a previously reported disease in dairy cows, so there isn't nearly enough data available on how [it] is affecting animals," Thompson says. "How is it moving through dairies? How quickly do animals recover? What does it look like when they do recover? All these questions and more need to be answered."

Many of those questions remain unaddressed a month after the initial federal announcement, even as more herds come down with the virus.
The efforts to gather the data to fill in these unknowns have also been piecemeal and slow, says Keith Poulsen, a clinical associate professor at the University of Wisconsin–Madison School of Veterinary Medicine, and the director of the Wisconsin Veterinary Diagnostic Laboratory. He says each state is acting differently rather than following a unified approach.

Another problem, he continues, is that reporting of sick cows is voluntary, and many farmers are averse to opening their operations up to government involvement. Still others are in denial about the seriousness of the threat the virus poses to the cattle industry. This creates a problem with data collection and responses to the virus.

​..."It is considered common knowledge that on the front lines of the outbreak there are more farms with affected cows" that have not reported them, Poulsen says. "It is very likely that there are more states involved, too." ....
"We really need some strong national leadership, and clearer guidance for how we move forward."

......
​​​​​​Sickened cows typically lose their appetite, become dehydrated, and take on a lackluster demeanor with fever—but so far they haven't succumbed to the virus.

Their milk productivity drops and, in severe cases, the milk they do produce begins looking "kind of yellow and more viscous," Poulsen says. Strangely, for now the disease seems to most seriously affect milking cows in mid- to late lactation. Younger heifers can also shed the virus in their milk, but without clinical signs. Within an affected herd, about 10% of animals come down with overt clinical signs....

Need for Unity....

....
​Trying to prevent the virus from reaching new herds is easier said than done, however. For example, although the USDA recommends that all dairy cows be tested for the virus before they are moved to a new facility, "I don’t know of anyone who is doing that," Armstrong says.

..One disincentive for testing is that no protocol currently exists defining how farmers whose herds do test positive "get out of the box," as Armstrong puts it—or the series of steps needed to resume business as usual after a test comes back positive and triggers USDA involvement. Poulsen suspects that this is probably why fewer new herds and positive tests have been reported in the Southwest states over the past few weeks: farmers want to avoid liability, risk, and government intervention......

Starting in late April, USDA began paying for pre-movement testing of H5N1 in cows. But significant funding gaps remain
​..Farms are not required to report affected cows, so many farms are not reporting because they have no financial or liability support, [which] poultry farms do," Poulsen says.

...​​​​​​ "I've got veterinarians who have cried over this because they're dealing with it and people are telling them it's not real," he says. ..... :tiphat:
​​​​​​https://www.thinkglobalhealth.org/a...s-express-confusion-over-us-response-bird-flu

 

[Treyfish]

State officials worry about financial impact after bird flu cases detected in Idaho cattle

Idaho has more cattle than humans, and it ranks third in the U.S. for milk production. Officials closely monitor cattle to limit bird flu.

BY: MIA MALDONADO - APRIL 26, 2024 4:30 AM

As cases of highly pathogenic avian influenza spread across U.S. cattle, Idaho officials say their biggest concern is the virus’ impact on Idaho’s economy. ..

​​​​​​On April 1, the Idaho State Department of Agriculture reported its first case of the bird flu in cattle in Cassia County. The cattle infected had been recently imported from Texas, Sydney Kennedy, the spokesperson for the department of agriculture told the Idaho Capital Sun.

And on Monday, the department confirmed a second herd in Cassia County is positive for the bird flu.
​....:tiphat:
https://idahocapitalsun.com/2024/04...r-first-bird-flu-in-cattle-detected-in-idaho/

 

[Treyfish]

Medical News in Brief
April 26, 2024 CDC: H5N1 Bird Flu Confirmed in Person Exposed to Cattle


Emily Harris
Article Information
JAMA. Published online April 26, 2024. doi:10.1001/jama.2024.6720​

….
Given the recent human infection, clinicians should consider H5N1 bird flu in people with acute respiratory symptoms, including conjunctivitis, who have been in contact with birds, livestock, or other animals within 10 days before symptoms began.​:tiphat:
https://jamanetwork.com/journals/jama/fullarticle/2818256

 

[Treyfish]

:tank:

I suggest they bring in the national guard, from each state, to do logistics and testing and quarantining of the farms.
They will need the guard from unaffected states...:earth:
Disregard what farmers don't want to do.
Bring whatever is needed to quarantine the area. :nuke:
Including trucks and medical tents. :doctor:
Check the workers and they're families. :magnify:
Check all the cows and other animals. "pigs and horses,cats and dogs. awprint::flamingo::bat:
​​​​​​Bring all test equipment :yinyang:
​​​​​​Carry a big bag of tamiflu :flask:

Damn the cost!.. :twocents:
They are already behind and better get with the program or catastrophe awaits! :taz: Hell it's here now!
Another week and it'll be too late if it's not already
.....or sit around and make a sandwich :tiphat:​​​​​​​

 

[Treyfish]

Bird flu cases are likely being missed in dairy workers, experts say

Experts maintain the milk supply is safe. Their focus is on keeping the people who work with cows from getting sick.​

April 26, 2024, 7:06 PM EDT
By Erika Edwards
Dr. Barb Petersen, a dairy veterinarian in Amarillo, Texas, had been caring for sick cows for several weeks in March when she and a colleague finally pinned down the cause of the illness among the herd: the H5N1 strain of the bird flu.

It was the first time the virus had been detected in cattle.
​
The sick cows, said Petersen, who owns Sunrise Veterinary Service, tended to produce milk that didn’t look quite right, and had mastitis, an inflammation of the udders.

During that same time, she said, dairy workers — including those who were never in close contact with the sick cows — also fell ill.

“People had some classic flu-like symptoms, including high fever, high fever, sweating at night, chills, lower back pain,” as well as upset stomach, vomiting and diarrhea, Petersen said. “They also tended to have “pretty severe conjunctivitis and swelling of their eyelids.”

Petersen noted that the people were never tested for H5N1; it’s possible that their symptoms were the result of another illness…..


​
At least 44 others may have been exposed, the CDC said. Some have been tested, while others were asked to monitor symptoms,such as cough, sore throat, pinkeye, fever, headache and diarrhea.

Dr. Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory, said he’s heard reports of flu-like illnesses on affected dairy farms.

“It’s certainly not a large amount,” he said, “but there’s probably a lot of cases
​…..
Our job right now is to protect farmworkers,” said Jennifer Nuzzo, director of the Pandemic Center at Brown University School of Public Health. “We can’t do that unless we know where the virus is or where it isn’t.”

It’s still unclear how the bird flu virus spreads from cows to people, though some experts said it could be through multiple paths, such as contact with milk, contaminated milking equipment, or even respiratory droplets.

“I think everything’s on the table at this point,” said Dr. Andrew……:tiphat:
https://www.nbcnews.com/health/heal...y-missed-dairy-workers-experts-say-rcna149520

 

[sharon sanders]

This version is killing barn cats. There are several more today documented.

 

[Pathfinder]

Why dangerous bird flu is spreading faster and farther than first thought in U.S. cattle
...
Lauren Pelley, Amina Zafar · CBC News · Posted: Apr 27, 2024 3:00 AM CDT | Last Updated: 5 hours ago
...
Michael Worobey, a researcher from B.C. who's now head of the department of ecology and evolutionary biology at the University of Arizona, said these cattle infections may have been "flying under our radar for months," providing ongoing opportunities for this virus to acquire adaptations that could lead to a flu pandemic.

"I think, in many ways, this is the biggest news story in the world right now."
...
In an interview with CBC News, he outlined H5N1's evolutionary tree, with a distinct branch of sequences linked to cattle. All those sequences share the same mutations, Worobey added.

"This is the hallmark of a single jump, that's at the root of this outbreak," he said.

And that jump likely occurred earlier than the first known cattle infections reported in late March.
...
The cattle sequences also contain "at least two distinct mutations" that are known for increasing the risk of a flu virus infecting and transmitting in humans, Worobey added.

"We just are producing more and more [opportunities] for evolution to arrive at something that can transmit in humans, and potentially kill a large proportion of them," he said.
...
At this point, it's still unclear how the virus is "sustaining transmission" in cattle populations, added virologist Angela Rasmussen, from the University of Saskatchewan's Vaccine and Infectious Disease Organization.

It's also likely the virus is being transmitted even when cows aren't showing symptoms — which have so far been mild, including low appetite and reduced milk production — several scientists agreed.

This week, officials announced dual discoveries of H5N1 in the lung of an asymptomatic cow in North Carolina, along with viral particles in pasteurized milk, suggesting infected cows almost slipped into the food supply chain.
...
Dr. Samira Mubareka, a clinician scientist at Sunnybrook Research Institute and the University of Toronto, is watching for any signs of the virus becoming more adept at transmitting between mammals, including humans.
...
She said even if this H5N1 virus doesn't infect more people, the virus has already hit animal health significantly and could affect food prices, food security and livelihoods.
...

https://www.cbc.ca/news/health/h5n1-second-opinion-april-27-cattle-1.7185165