The Summary
- The bird flu outbreak took several concerning turns this year, with the number of human cases up to at least 65.
- Experts outlined several indicators that the virus spread is going in the wrong direction.
- Among them are recent detections of the virus in wastewater and signs of dangerous mutations.
Perhaps the long-simmering danger of avian flu is about to explode.
A number of alarming advancements in the virus’s transmission have occurred this year. At least 65 individuals have tested positive with the virus since April, marking the first instances of the virus in the United States other than a single incident in 2022. This year, the virus has affected dairy cow herds in 16 states. On Wednesday, the Centers for Disease Control and Prevention verified that a critically ill patient in Louisiana had contracted the nation’s first severe bird flu illness. Additionally, in response to widespread outbreaks in cows and poultry, California Governor Gavin Newsom last week issued a state of emergency.
According to Dr. Peter Chin-Hong, a medical professor who specializes in infectious disease research at the University of California, San Francisco, the traffic light is shifting from green to amber. Numerous indicators are pointing in the wrong way.
According to the CDC, there is currently no evidence of human-to-human avian flu transmission, and there is little immediate risk to public health. However, there are four main indicators that scientists are becoming more concerned.
For starters, the H5N1 avian flu virus has spread unchecked among animals, including cows that regularly come into touch with humans. Furthermore, the virus is spreading beyond agricultural animals, as evidenced by detections in wastewater.
In addition, studies on the development of the pathogen have revealed that it is changing to better fit human receptors and that it will require fewer mutations to spread among humans, despite the fact that there are a number of human instances in which the source of infection has not been found.
These signs collectively imply that the virus has begun to move toward becoming the next pandemic, according to researchers.
We’re in a really vulnerable position at the moment, according to Scott Hensley, a University of Pennsylvania microbiology professor.
Widespread circulation creates new pathways to people
The virus has expanded widely among wild birds, commercial poultry, and wild mammals like sea lions, foxes, and black bears since the start of this avian flu outbreak in 2022. The U.S. Agriculture Department reports that over 125 million chicken birds have been culled or perished from diseases in the United States.
When dairy cows started getting sick, eating less feed, and producing milk that was discolored in March, it was an unpleasant surprise.
Because infected cows shed a lot of the virus through their mammary glands, research revealed that the virus was spreading quickly and effectively between cows, most likely through raw milk. Farm cats and raccoons also seemed to become ill after consuming raw milk.
Humans who come into contact with diseased animals are more likely to be exposed as more animals get affected.
Jennifer Nuzzo, an epidemiology professor and the head of the Pandemic Center at the Brown University School of Public Health, stated that the more people infected, the greater the chance that mutations will take place. I dislike allowing the virus to spread and cause a pandemic.
Cows had not been the focus of influenza prevention initiatives before this year.
NBC News reported last summer that Andrew Bowman, a professor of veterinary preventive medicine at Ohio State University, stated, “We didn’t think dairy cattle were a host for flu, at least a meaningful host.”
However, the virus has already been found in at least 875 cow herds in at least 16 states, as well as in domestic cats that drank raw milk and raw (unpasteurized) milk sold in California.
According to Chin-Hong, raw milk and cheese products are currently the areas where a community and customers are directly at risk. That risk was smaller a year ago, or even a few months ago.
Cases with no known source of exposure
Poultry and dairy farmworkers have been the primary source of human H5N1 infections. However, no source of infection has been found in a number of perplexing cases.
The first was a hospitalized patient in Missouri who recovered after testing positive in August. Another was a child from California who was reported infected in November.
Health officials in Delaware also announced this week that a person who had no known contact with animals or poultry had contracted H5N1. However, the CDC views it as a probable case because testing was unable to prove that the infection was bird flu.
A Canadian kid who had no known exposure to farm or wild animals was admitted to the hospital in early November after catching H5N1. According to the virus’s genetic content, it resembled a strain that was circulating in poultry and ducks.
Some experts are becoming concerned about such unexplained cases.
According to Nuzzo, this implies that the virus may be significantly more widespread and that more people may be exposed to it than we previously believed.
Rising levels of bird flu in wastewater
Scientists are keeping an eye out for viral pieces in wastewater to have a better understanding of the geography of avian flu transmission.
According to Amy Lockwood, the public health partnerships director at Verily, a business that supplies wastewater testing services to the CDC via a program called WastewaterSCAN, we’ve seen detections in a lot more areas and in a lot more frequent ways in recent months.
Approximately 19% of the locations in at least 10 states that are part of the CDC’s National Wastewater Surveillance System reported positive detections earlier this month.
It is impossible to determine if the virus fragments were obtained from humans or animals. Some might have resulted, for instance, from feces from wild birds that get into storm drains.
“There is a lot of H5 virus out there, but we don’t think any of this is an indication of human-to-human transmission right now,” said Peggy Honein, head of the CDC’s Division of Infectious Disease Readiness & Innovation.
According to Lockwood and Honein, wastewater detections have typically occurred around chicken farms or dairy processing facilities, but in recent months, enigmatic hot spots have appeared in areas devoid of these agricultural facilities.
We are in the midst of a very massive numbers game, Lockwood added, adding that we are beginning to see it in more and more places where we are unsure of the source automatically.
One mutation away?
Until recently, researchers studying the evolution of viruses believed that H5N1 would require only a few modifications to spread easily from person to person.
However, a single mutation might cause the virus that is circulating in cows to connect to human receptors, according to research published this month in the journal Science. (The entire infectious virus was not being studied; only its proteins were.)
We don’t want to presume that a pandemic is going to occur as a result of this finding. “We just want to emphasize that this increases the risk,” said Jim Paulson, co-author of the article and the chair of molecular medicine at Scripps Research.
Separately, in recent months, researchers have discovered troubling components in a different strain of the virus that was discovered in the Canadian girl who became gravely ill. According to Hensley, samples of the virus revealed evidence of changes that would render it more susceptible to human-to-human transmission.
It’s doubtful that the virus had those changes when the kid was exposed, according to a CDC representative.
According to the spokesman, the combination of modifications in this virus most likely happened after the patient had been infected for a long time.
According to the spokeswoman, the agency’s investigations do not indicate that the virus is evolving to spread easily between people.
The viral strain that caused the first serious case of bird flu in the United States was linked to the infection that infected the Canadian teenager, according to the announcement made on Wednesday.
Dr. Demetre Daskalakis, director of the National Center for Immunization and Respiratory Diseases, said the CDC is assessing a sample from that patient to determine if it has any concerning mutations.
Meanwhile, Hensley expressed his worry that flu season would provide the virus with a quick route to evolution. Co-infection with a seasonal flu virus and avian flu can result in the exchange of genetic code fragments.
There s no need for mutation the genes just swap, Hensley said, adding that he hopes farmworkers get flu shots to limit such opportunities.
Future testing and vaccines
Experts said plenty can be done to better track bird flu s spread and prepare for a potential pandemic. That work has already started in part.
On Tuesday, the USDA extended the use of bulk milk testing to 13 states, which accounts for roughly half of the country’s milk supply.
According to Nuzzo, the effort cannot be increased quickly enough.
We have taken way too long to implement widespread bulk milk testing. According to her, that is how we are identifying the majority of outbreaks on farms.
At the same time, Andrew Trister, chief medical and scientific officer at Verily, said the company is working to improve its wastewater analysis in the hope of identifying concerning mutations.
The USDA has alsoauthorized field trials to vaccinate cows against H5N1. Hensley said his laboratory has tested a new mRNA vaccine in calves.
For humans, the federal government has two bird flu vaccines stockpiled, though they wouldneed Food and Drug Administration authorization.
Nuzzo said health officials should offer the vaccines to farmworkers.
We should not wait for farmworkers to die before we act, she said.
Additionally, scientists are developing new mRNA vaccines against H5N1. This type of vaccine, which was first used against Covid-19, can be more quickly tailored to particular viral strains and also scaled more quickly.
Hensley s lab in Mayreported that one mRNA vaccine candidate offered protection against the virus to ferrets during preclinical testing. Another candidate under development by the CDC and Moderna hasalso showed promising resultsin ferrets, which are often used as a model for humans to study influenza.
Now we just have to go through the clinical trials, Hensley said.
CORRECTION(Dec. 22, 2024, 5:10 p.m. ET): A photo caption in a previous version of this article misstated when the Agriculture Department ordered that the country’s milk supply be tested. It was Dec. 6, not last week.
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