The US is entering a riskier season for spread of H5N1 bird flu. Here’s why experts are worried.(CNN NEWS)_
With the approach of fall and cooler weather across the United States, officials say the risk posed by the H5N1 bird flu virus could rise — and they’re taking steps to prevent the creation of a hybrid flu virus that could more easily infect humans.
Fall and winter months present more opportunities for H5N1 to spread and change since both cows and other flu viruses will be on the move. While most human infections in the current outbreak have been mild and self-limiting, each new host gives the virus a chance to get better at infecting people.
“To be clear, we have no evidence so far that this virus can easily infect human beings or that it can spread between human beings easily in a sustained fashion,” said Dr. Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health. “If it did have those abilities, we would be in a pandemic.
“The second we know that someone gave it to someone else relatively easily, that’s a new pandemic, and it will be around the globe, probably in a matter of weeks,” Nuzzo said at a seminar hosted by the Health Coverage Fellowship.
The concern comes as scientists are urgently trying to solve the mystery of how a person in Missouri who had no contact with animals became infected by a type of bird flu.
The US is entering a riskier season for spread of H5N1 bird flu. Here’s why experts are worried.(CNN NEWS)_
FILE – The Centers for Disease Control and Prevention is shown, March 15, 2020, in Atlanta. (AP Photo/John Bazemore, File)
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Few details have been released. The person had “significant underlying health conditions” that probably made them more susceptible to the infection, Dr. Nirav Shah, principal deputy director of the US Centers for Disease Control and Prevention, said Thursday.
The patient tested positive for the flu after being hospitalized August 22, was treated with antiviral medications and has since recovered and returned home.
Additional testing by the Missouri State Public Health Laboratory confirmed that the person had a type of H5 flu, which is an uncommon subtype. Only 13 other H5 infections have been reported in humans in the US this year. Aside from the Missouri case, all have been in farm workers who had been in direct contact with infected birds or cows.
The CDC has confirmed that the Missouri case was an H5 infection and is now trying to sequence the rest of the virus’ genome to find out whether it is related to those infecting poultry and dairy cattle. It’s not clear whether the agency’s scientists will be successful, since there was little virus in the patient’s samples to work with. So far, CDC scientists had been able to sequence only part of the virus’ genetic material.
“The data that we do have and that have been generated thus far show an H5 virus that is closely related to the H5 virus circulating among dairy cows,” Shah said.
Investigators have also interviewed the patient and are tracing their recent contacts. There’s no indication that the person passed the infection to anyone else, and there’s no unusual flu activity in the area where the person lives, Shah said.
“Seeing that someone is in the hospital with possible H5N1 heightens my worry,” Nuzzo said. “It not only heightens my worry for the farm workers,” who are most at risk from infection, she said, “but it also heightens the worry that this we’re allowing this virus to gain new abilities.”
The US is entering a riskier season for spread of H5N1 bird flu. Here’s why experts are worried.(CNN NEWS)_
With herds on the move, risk increases
H5N1 caught scientists by surprise when an outbreak in US dairy cattle emerged in March. New cases slowed in the summer, when dairy cows move around less, partly due to heat and partly because demand for milk drops during the summer, when school is out, Dr. Eric Deeble, deputy undersecretary for marketing and regulatory programs at the US Department of Agriculture, said in August. But that starts to change in the fall, when farmers move cows so they can graze on the remnants of fields that have recently been harvested.
Greater movement of cattle could give the H5N1 virus more opportunities to spread.
Bird flu poses a threat to some farm workers. (Photo by Smith Collection/Gado/Getty Images).
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“It is always of concern when folks are moving animals,” Deeble said.
The USDA has ordered the testing of dairy cows before they travel between states, but there’s no such requirement for cattle that are moving within the same state.
The order also doesn’t require the testing of every animal within large groups, and there’s concern that cows that are infected without symptoms may be moved undetected.
That concern was heightened after three dairy herds in California’s Central Valley tested positive for H5N1 last month. As of September 12, the total number of infected herds in California had jumped to eight, Deeble said Thursday.
California is home to about 1.7 million dairy cows, about one-sixth of the national total, making it the nation’s largest dairy producing state.
How and when the virus made its way to California is still under investigation. But genetic testing at the USDA’s National Veterinary Services Laboratories shows that the virus that infecting the California herds is very closely related to the viruses that have infected more than 200 herds from 13 other states, Deeble said.
The first infections of cows with the H5N1 virus were confirmed in herds in Texas and Kansas in late March. Evolutionary biologists think cows became infected months earlier, perhaps around the first of the year, when the virus probably spread from migrating birds who were carrying it.
The US is entering a riskier season for spread of H5N1 bird flu. Here’s why experts are worried.(CNN NEWS)_
Cambridge, MA – May 14: From left, Jon Arizti Sanz, PhD, Postdoctoral Fellow with Liam Alec Stenson Ortiz, research associate working in the lab. The Broad institute, Sabeti Lab is testing purchased milk at area grocery stores for the presence of bird flu. (Photo by David L. Ryan/The Boston Globe via Getty Images)
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The finding that the virus infecting the herds in California is genetically related to these first infections is important because it means they almost certainly are not the result of another crossover event from migrating birds to cows. Instead, the virus probably made its way to California through cow-to-cow spread that still hasn’t been controlled.
“So we were dealing essentially with one variant from the very beginning of this outbreak,” Deeble told CNN. “That information has been shared back with California, and so they’re continuing their epidemiological investigation with that knowledge in hand.”
Wastewater testing has been picking up H5 viruses in California since March 18, said Dr. Marlene Wolfe, assistant professor of environmental health at Emory University and program director for WastewaterScan, a monitoring network directed by researchers at Stanford and Emory universities and funded by the Sergey Brin Family Foundation.
California is one of nine states — of 40 being monitored in their network — where H5 viruses have been found in wastewater.
Wastewater testing can pick up viruses with the H5 proteins, but it can’t tell whether those viruses came from birds, cows, other animals or even discarded milk that had found its way into the sewage system. So far, though, most states that have had H5 proteins turn up in wastewater have also reported infected herds.
“So far, eight of these states have had outbreaks reported in cattle. The one state with an H5 detection that has not had an H5N1 cattle outbreak is Arkansas,” Wolfe wrote in an email.