Just One Human Is Infected by Bird Flu in the US. More Cases Are Likely
(Bloomberg) -- It’s spreading rapidly among cows. It’s also infecting skunks, mountain lions and red foxes.
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Yet as the highly contagious avian flu affects mammals across the US, just one human case has been reported so far.
But that’s probably only because there is extremely limited testing of people underway to detect it. State governments and farm owners have kept Centers for Disease Control and Prevention teams from conducting on-the-ground investigations that would offer a fuller picture of the prevalence of the virus in humans.
That threatens to impair federal officials’ response to an outbreak that many experts view as the biggest test for pandemic readiness systems since Covid-19. The recent patient is recovering after experiencing eye redness as their sole symptom. However, avian flu typically kills half the people known to have been infected, hinting at the danger it poses if it were to spread widely.
The CDC does not have authorization to carry out on-the-ground investigations without an invitation, and the states that have confirmed infected cattle say they have not made such an overture to the agency.
Private dairy farms would also have to welcome the CDC investigators, a fraught proposition in an industry heavily reliant on immigrant workers who are often leery of interacting with government officials and worried about losing income if they test positive. Farms may also be reluctant to scour for infected cows, out of concern that might have downsides for their low-profit margin businesses.
“The CDC is not able to go in and do the type of testing and investigative work they need to do,” Abraar Karan, an infectious disease researcher at Stanford University, said. “That’s a huge problem and it’s a blatant issue.”
The CDC says the current risk to the general public from bird flu is low, because it’s not known to transmit efficiently from person to person. But each infection in a cow or human provides an opportunity for the virus to mutate and become better adapted to mammalian respiratory cells.
Key to understanding that risk – and preventing the emergence of a deadly pandemic – is the ability to detect the infection and track molecular changes in the virus.
“We’re playing with fire,” said Sam Scarpino, a professor at Northeastern University, who helped lead pathogen surveillance at the Rockefeller Foundation during the coronavirus pandemic. “We’re really not doing the surveillance to say that it’s not here.”
On-The-Ground Testing
CDC Director Mandy Cohen said her agency is prepared to conduct on-the-ground bird flu testing and other forms of surveillance.
“We are ready to deploy,” Cohen said in an interview Monday. “We have been for weeks.” Those on standby at the CDC include multilingual and multidisciplinary epidemiological teams.
Yet the nine states with infected cattle — Texas, New Mexico, Michigan, Kansas, Idaho, Colorado, North Carolina, Ohio and South Dakota — said in statements they have not invited the CDC.
In New Mexico and Texas, the only two states that have reported conducting testing of their own, the scope of that work has been limited. New Mexico tested three people for avian flu, a spokesperson said in an email.
The Texas Department of State Health Services tested about 20 people, with one positive case in a dairy farm worker. The worker showed signs of conjunctivitis with red, swollen eyes and returned to work the day after testing. A spokesperson for the department said it hasn’t invited the CDC “because we have not found any dairy farms interested in participating in an epidemiological field study.”
Since March, more than 30 people have been tested for novel influenza A, the broad category of flu that includes H5N1, and over 220 have been monitored for symptoms, many of whom are being asked to self-report signs of disease, according to the CDC.
The CDC is monitoring multiple flu indicators, and Cohen notes that data from emergency rooms and commercial laboratories across the US isn’t currently showing concerning patterns.
“The good news is we’re not seeing anything unusual,” Cohen said, such as a spike in doctors ordering flu tests.
Yet she also stressed the need to continue to work with agriculture partners – especially given the novel nature of how this strain of bird flu is spreading.
“There is a very robust way in which we’ve worked with our poultry farmers, but this is new in cattle,” Cohen said.
‘Huge Problem’
The FDA found traces of the H5N1 virus in 1 in 5 retail milk samples. Although pasteurization has been shown to render the pathogen harmless, that incidence shows it has spread widely among cows. In the US, some 36 dairy herds are known to have been affected.
The USDA recently said it’s scouring for manufacturers who are interested in making a safe and effective vaccine for use in cattle targeting the virus.
The people most likely to be infected – dairy farm workers who have their hands on cows regularly – aren’t necessarily going to doctors for treatment, community health workers say.
Wastewater testing in Texas found H5N1 traces, which could be attributed to humans or animals with the virus. Of hundreds of sites looked at weekly by a research group, a trio were tested for genetic markers of H5N1, and all three were confirmed to have it. Researchers wrote that cow’s milk entering sewage systems is a likely explanation for those findings.
“We’ve almost certainly missed human cases,” Scarpino said, referencing the Texas wastewater findings. “The real question we need to answer is: Are there thousands of flu cases we missed, or a handful?”
Worker Reluctance
Even if the CDC were to gain authorization from states and farms to perform onsite testing, it would face additional challenge: Workers would have to agree to participate, and many of them would likely be hesitant to do so.
Fear of job loss, language barriers, transportation costs and distrust in public health systems are all factors that might deter migrants from consenting to test, said Bethany Alcauter, director of research at the National Center for Farmworker Health. She said the situation reminds her of the early days of the coronavirus pandemic, when workers were reluctant to test and the illness wasn’t well understood.
Lus Chavez, rural outreach director at Family Support Services in Amarillo, Texas, said she spoke with dairy workers in late February with flu-like symptoms including congestion, but they tested negative for flu and Covid. The farm workers, she said, were convinced it was a new strain of Covid that wasn’t showing up on tests.
Chavez said she has been contacted by the Texas health department to advertise that it can provide voluntary tests, but workers are reluctant to do so out of fear of retaliation for raising concerns or worries about losing pay.
Even if workers elect to test, there is no requirement to reveal where they work, another challenge for authorities trying to track and contain the virus.
The CDC is engaged in discussions with multiple states about setting up field investigations to answer questions about the ongoing outbreak, including by examining flu antibodies in blood samples from farm workers in order to see if any of them had been previously infected. The CDC would help establish protocols for studies that would allow data to be standardized across states. Such an effort could similarly face hesitation from farms and staff.
It’s not just a dearth of bird-flu testing that concerns public health experts. A lack of funding and research, some say, has also left the US flatfooted if a wider outbreak of bird flu – or any other deadly virus – takes hold.
“We’re not going to be ready,” Katrine Wallace, epidemiologist at the University of Illinois, said. “We’re not even dealing with what’s right in front of us.”
--With assistance from Madison Muller.
(Updates with USDA announcement, adds details about wastewater treatment study)
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