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As avian influenza spreads rapidly across the globe, the H5N1 bird flu virus is poised to mutate and potentially cause more significant issues for humans. Experts predict that new flu symptoms in high-risk individuals will likely start appearing in health systems this summer, marking a critical period for monitoring and response.
Vivien Dugan, PhD, director of the influenza division at the US Centers for Disease Control and Prevention (CDC), emphasized the need for vigilance. “There is a broad range of symptoms to be watching for,” Dugan stated. “Some of this will not be obvious or at the forefront of our minds.”
Dugan leads a team of CDC scientists collaborating with the US Department of Agriculture, the US Food and Drug Administration (FDA), and state and local health departments to track and respond to the H5N1 bird flu outbreak sweeping through the US. Since 2022, avian influenza A viruses have been detected in over 9,300 wild birds across 50 states and territories and in commercial and backyard flocks.
Florian Krammer, PhD, a professor of vaccinology at the Icahn School of Medicine at Mount Sinai in New York, highlighted the global nature of the issue. “Globally, we’ve seen tons of exposure in cities around the world and even in the birds here in New York City where I am,” he said.
The virus, shed by birds through saliva, mucus, and feces, can infect people or other animals through close, unprotected contact with contaminated environments. In March 2024, H5N1 bird flu was reported in dairy cows for the first time, with infections confirmed in 101 dairy herds across 12 states and in several dairy workers.
From Birds to Cattle and Farm Workers
The National Veterinary Services Laboratories confirmed the infections were highly pathogenic avian influenza H5N1 clade 2.3.4.4b of Eurasian lineage. “I was surprised when H5 was introduced to dairy cattle in this way,” Dugan noted. “Influenza viruses are always surprising us, and it reminds me to stay humble and keep an open mind when dealing with them.”
Although human infection from close contact with animals is rare, it can lead to upper respiratory tract symptoms such as shortness of breath, cough, sore throat, or runny or stuffy nose. Other symptoms may include muscle or body aches, headache, fatigue, fever, conjunctivitis, diarrhea, nausea, vomiting, and sometimes seizures.
While the risk to the general public remains low, authorities recommend that people working with animals practice stringent hygiene and wear personal protective equipment.
Asking Unusual Questions
Healthcare providers are encouraged to inquire about patients’ occupational exposures when they present with flu symptoms. Meghan Davis, PhD, associate professor at the Johns Hopkins Bloomberg School of Public Health, stressed the importance of asking about any direct contact with dairy cows, poultry, pigs, wild birds, or wild mammals.
Davis also highlighted concerns about farm-to-farm transmission and the potential for virus spread within families due to shared employment in agricultural settings. “We need to be on the lookout for possible transmission within families,” she said.
Spotting New Cases
Since April 2024, three human cases of avian influenza have been reported following exposure to dairy cows. Krammer warned against complacency: “What we don’t want to see this summer is an unusual human cluster of influenza. It’s important we keep a close, watchful eye for this.”
The infrastructure built during the COVID-19 pandemic has equipped teams to monitor and respond to this new crisis. Laboratories are prepared to help with testing, and healthcare providers are urged to collect specimens from patients with flu symptoms promptly.
Antiviral Drugs
There are four FDA-approved antivirals for influenza: Oseltamivir phosphate (Tamiflu), Zanamivir (Relenza), Peramivir (Rapivab), and Baloxavir (Xofluza). Treatment for suspected or confirmed avian influenza is recommended as soon as possible, despite the lack of clinical trials specifically for H5N1 in humans.
“We can’t afford to wait this summer,” Krammer said. “We have an opportunity right now to stop this in cows before we risk infecting more people. I hope we do.”
Conclusion
The coming months will be crucial in preventing the spread of H5N1 bird flu from animals to humans. Vigilance, early detection, and prompt treatment are essential in averting a potential new pandemic. Authorities and healthcare providers must remain alert and proactive to mitigate the risks and protect public health.
