Amid widespread gaps in US testing for H5N1, a type of feel fluand since a second case has been detected in humans, scientists are turning to more creative ways to monitor 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 monitor this outbreak as they prepare for the next pandemic.
A new one dashboard to monitor influenza A in wastewater across the country was launched last week by the Centers for Disease Control and Prevention (CDC). It does not track H5N1 specifically, but the highly pathogenic bird flu variant is part of the influenza A family.
The dashboard helps identify hotspots in the US where influenza A is on the rise — and since flu rates among people are low this time of year, such a surge could alert scientists and the public to possible outbreaks of H5N1.
“I’m really happy 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 laboratory lead for wastewater surveillance in Missouri.
Another project turns to citizen scientists – high school students New York City – to taste bird droppings for infectious diseases.
Volunteers, clad in personal protective equipment, are trained in taking fecal samples from local parks, then 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 in late 2022, according to a new study.
“There’s a lot of potential for citizen science, especially to increase the scope of surveillance” of pathogens, said Philip Meade, lead author of that study and a researcher at the Mount Sinai Laboratory.
“It is very difficult to have a total understanding of the viruses circulating in our environment,” he said.
The citizen science program, called Virus Hunters, could be expanded to other migratory birds along the West Coast and the Midwest, Meade said.
“The more people you have on the ground helping us generate the data now and understand what’s happening, the better it is for us and also for wildlife,” says Christine Marizzi, a co-author of the study and director of community. science for BioBus, the mobile research lab that works 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 it together with the community. We actively involve the community from the beginning,” she said. “Getting information out so we can build trust is what you really need once the next pandemic rolls around. It’s going to be very, very important.”
Part of the challenge of monitoring the emergence of viruses from animals is the magnitude 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 was gaps in testing during this outbreak of bird flu, as farms and workers face negative consequences if they test positive. Testing wastewater helps officials understand which pathogens are circulating without directly testing animals and people.
“If any of the farms are on municipal sewage, then we can test for that – we don’t have to go on the farms,” Johnson said. “I think it’s a really good idea, not just for dairy, but especially downstream of meat processing plants, so we can track if it spreads” to non-dairy animals.
Dairy cow infections are usually detected by testing their milk, as the udders have been shown to have high concentrations of the influenza virus – but in other animals that are not lactating, it can be difficult to know where to test the animal for get accurate results. “Testing downstream of meat processing plants is a good idea because it doesn’t matter what part of the cow it’s in,” Johnson said.
H5N1 has been detected in the wastewater of nine out of 10 Texas cities that are in a recent preprint study. The bulk of the virus probably comes from animals, but human infections cannot be ruled out, the authors concluded.
“Whether it’s coming from cattle or people or birds or whatever, let’s get an idea of how many there are, 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 better.”
If statewide influenza 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.
Monitoring of wastewater can also help detect ongoing transmission from farms, particularly to new species.
This cow-adapted flu variant may continue to acquire mutations as it trickles 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 any time a virus like this enters a mammalian host and stays there and circulates in that host, that’s something that’s very concerning to us,” Meade said.
“When it comes to pigs, that’s when we have to start getting nervous,” Johnson said. Typically, pigs are only checked for diseases like this when they become ill, but asymptomatic infections can go unnoticed. “If the pigs don’t get sick, they could already be in pigs and we wouldn’t know it.”
Undetected infections among humans will also be a major concern.
“If we missed it for five months in dairy cattle, we could miss it in something else. And it could be something much more worrisome than dairy cows,” Johnson said.
