Amid widespread gaps in US testing for H5N1, a type of bird flu, and as a second case among humans has been detected, scientists are turning to more creative ways of monitoring the outbreak – especially in human and animal feces.
Scientists and officials are expanding wastewater monitoring across the US and engaging community members to collect waste samples from birds. They hope to keep tabs on this outbreak while preparing for the next pandemic.
A new dashboard to monitor influenza A in wastewater across the country was launched by the Centers for Disease Control and Prevention (CDC) last week. It doesn’t track H5N1 specifically, but the highly pathogenic avian influenza variant is part of the flu A family.
The dashboard helps identify hotspots in the US where flu A is surging – and, since flu rates among people are low this time of year, such a surge can alert scientists and the public to potential outbreaks of H5N1.
“I’m really pleased to see that they’re sharing the data that they have,” said Marc Johnson, a professor at the University of Missouri School of Medicine and the lab lead for wastewater surveillance in Missouri.
Another project turns to citizen scientists – high school students in New York City – to sample bird droppings for infectious diseases.
Volunteers, swathed in personal protective gear, are trained in taking fecal samples from local parks, and then they work with scientists at the Icahn School of Medicine at Mount Sinai to analyze which pathogens are present.
This is how H5N1 was first discovered in New York City in late 2022, according to a new study.
“There is a lot of potential for citizen science, particularly to increase the scope of surveillance” of pathogens, said Philip Meade, lead author of that study and a researcher at the Mount Sinai lab.
“It is very difficult to have a total understanding of the viruses that are circulating in our environment,” he said.
The citizen science program, called Virus Hunters, could be expanded to other migratory bird flyways along the west coast and the midwest, Meade said.
“The more people you have on the ground that help us to generate the data now and understand what’s happening, the better this is for us and also for the wildlife,” said Christine Marizzi, a co-author of the study and director of community science for BioBus, the mobile research lab working with students.
Citizen science programs don’t just expand the number of people collecting samples, Marizzi said. They also build trust in science among communities.
“We do this together with the community. We actively involve the community from the beginning,” she said. “Getting information out so we can build trust that you really need once the next pandemic is rolling. That’s going to be very, very important.”
Part of the challenge of monitoring the emergence of viruses from animals is the immensity of the task. Usually, animals (and people) are only tested when they are sick – but scientists are now learning that H5N1 can circulate asymptomatically in cows and possibly other animals.
Non-invasive sampling like this can monitor for pathogens even when no symptoms are present.
There have been gaps in testing during this outbreak of avian influenza, as farms and workers face negative consequences if they test positive. Testing wastewater helps officials understand what pathogens are circulating without testing animals and people directly.
“If any of the farms are on municipal sewage, then we can test for it – we don’t have to go on the farms,” Johnson said. “I think this is a really good idea, not just for dairy but particularly downstream of meat-processing plants, so we can keep an eye on whether it’s spread” into non-dairy animals.
Dairy cow infections are usually detected by testing their milk, since the udders have proven to have high concentrations of the flu virus – but in other animals that aren’t lactating, it might be difficult to know where to test the animal to get accurate results. “Testing downstream of meat-processing plants is a great idea because it doesn’t matter what part of the cow it’s in,” Johnson said.
H5N1 was detected in the wastewater of nine out of 10 Texas cities surveyed in a recent pre-print study. The bulk of the virus is likely coming from animals, but human infections can’t be ruled out, the authors concluded.
“Whether it’s coming from cattle or humans or birds or whatever, let’s get an idea of how much is there, so if there’s a change, we know to pay attention,” Johnson said. “We need a baseline of what’s going on so we can see if things are getting worse or getting better.”
If nationwide flu A monitoring had been in place a few months ago, he said, officials may have detected the H5N1 outbreak in cows much sooner. Scientists believe the current outbreak began in late 2023, but it was only detected at the end of March.
Wastewater monitoring could also help detect onward transmission from farms, especially into new species.
This cow-adapted flu variant could continue gaining mutations as it spills back into bird populations or spills over into new species.
“When viruses spend time in different hosts, they evolve to become better at replicating in those hosts. So anytime a virus like this enters a mammalian host and stays there and circulates in that host, it’s something that’s very worrisome to us,” Meade said.
“If this gets into pigs, that’s when we need to start getting nervous,” Johnson said. Typically, pigs are only checked for illnesses like these when they get sick, but asymptomatic infections could go unnoticed. “If the pigs aren’t getting sick, they could be in pigs already and we wouldn’t know it.”
Undetected infections among people would also be a major concern.
“If we missed it in dairy cattle for five months, we could miss it in something else. And it could be something much more concerning than dairy cows,” Johnson said.
