A recent human infection of avian flu in Texas, coming just days after the first infections of U.S. livestock, has spurred research into the latest version of the virus as vaccine makers prepare for the unlikely event that it mutates to the point where it can cause a human pandemic.
Meanwhile, farmers working to contain the threat to their flocks are now concerned about their herds, and testing continues on vaccine candidates to protect birds.
The human infection with avian flu (H5N1) reported in Texas on April 1—the second ever recorded in the U.S.—caused only mild symptoms, and risk for humans, livestock, and our food supply remains low, experts say. However, viral mutations could change the risk level.
Controlling the situation requires One Health solutions that address the health of humans, animals, and the environment holistically. The biotech industry’s responses include developing vaccines for humans and animals, and using CRISPR to grow chickens with immunity to avian flu. The industry could benefit from the kind of government collaboration we saw during the pandemic.
“We need to be prepared with vaccines before H5N1 becomes a public health concern,” says Phyllis Arthur, SVP of Infectious Diseases & Emerging Science Policy at the Biotechnology Innovation Organization (BIO).
“Fortunately, pandemic influenza is a place where there is considerable infrastructure because of the great work that’s already been done to address seasonal flu and previous pandemics,” she said. “The vaccine industry can quickly work with government leaders to start developing vaccines against a novel pandemic flu strain mainly because we have this infrastructure and an existing public-private partnership.”
The impact on cattle and humans
The latest genetic sequencing of the viruses that infected the person in Texas, and cattle in several states, shows no dangerous mutations, according to the Centers for Disease Control and Prevention (CDC).
“Both cattle and human sequences maintain primarily avian genetic characteristics and for the most part lack changes that would make them better adapted to infect mammals,” CDC says.
“Any allusion to the bird flu being ‘the next pandemic’ at this stage would be alarmist,” says Lynne Finnerty, BIO Senior Director of Public Affairs. “We must take the outbreak seriously, but we don’t need to make it seem more serious than it is.”
The risk of avian flu to cattle is also considered low, as is any spread between cows. “Spread of H5N1 bird flu viruses from mammal to mammal is thought to be rare, but possible,” according to the CDC.
In the cases reported in March—in Idaho, Kansas, Michigan, New Mexico, Ohio, and Texas—the cattle were apparently infected through exposure to infected poultry. Investigation was said to be continuing into more rececent cases, reported April 10 in North Carolina and April 11 in South Dakota.
None of the cattle were seriously ill, and though their milk was destroyed, pasteurization would remove avian flu viruses from the milk, making it safe to consume, the U.S. Department of Agriculture (USDA) says.
More extensive virus mutations that could lay the groundwork for a human pandemic do not appear to be imminent. Analysis of a virus that infected a Chilean man last year had two mutations in the PB2 gene that have been shown to help the virus better replicate in mammals. These mutations had been seen before, and several further mutations would be required before the virus has the ability to spread in humans, Bio.News reports.
How we can protect humans from bird flu
The U.S. Government maintains a stockpile of bird flu vaccines for humans in case it’s needed. To ensure drug manufacturers have the ability to produce updated vaccines quickly, the CDC is constantly monitoring the changing avian flu virus and keeping an updated candidate vaccine virus (CVV). CDC says it has a CVV sample to match the hemagglutinin protein of recently detected clade 2.3.4.4b A(H5N1) viruses in birds and mammals.
The vaccine industry is increasing the pace of research, working with governments to ensure that there is a stockpile of vaccines updated against the newest version of the virus, in case a pandemic response is needed—something experts say seems unlikely in the near future.
CDC says it is also continuously monitoring viruses to spot changes that would make the virus more capable of spreading between mammals or humans. If the chance of contagion between humans requires a vaccine, the CDC and the biotech industry should be ready to respond.
Among the few humans infected with H5N1, commercially available antivirals are effective. CDC monitors changes in the viruses that might give them some immunity to antivirals, and thus far there is no such evolution seen.
How we can protect animals from bird flu
While the USDA has licensed four vaccines that can protect birds against earlier types of bird flu, no vaccine is yet approved for the current strain, H5N1 clade 2.3.4.4b, which has been driving the global outbreak started in 2021.
“We are probably 18 months or so away from being able to identify a vaccine that would be effective for this particular (avian flu) that we’re dealing with now,” Agriculture Secretary Tom Vilsack told a Feb. 14 Congressional hearing, Reuters reports.
USDA says it plans to discuss poultry vaccinations with trading partners. Vaccinated birds test positive for the flu, which has led to import restrictions.
A survey by the World Organisation for Animal Health (WOAH) found that only 25% of its member countries would accept imports of vaccinated poultry, according to Reuters. The United States currently rejects such poultry. The U.S. government said last year that France’s decision to vaccinate ducks against avian flu will trigger restrictions on imports of French poultry.
For now, USDA says it is using other biotech measures to contain the avian flu while considering vaccination.
A One-Health vision
The WOAH recommends a One Health approach to avian flu. The World Health Organization (WHO) says in a recent report that avian flu provides a clear illustration of why a One Health approach is needed for many of our health challenges.
“In addition to the public health concerns that are currently already widely addressed, One Health requires a focus also on biodiversity conservation and environmental impacts, wildlife health, and livestock production and consumption, and both wild and domestic animal health and welfare concerns,” says the WHO. “The recent unprecedented shift in the ecology of highly pathogenic avian influenza (HPAI) illustrates this need.”
As BIO’s Arthur notes, “It’s obvious that human health is closely intertwined with the health of the environment we live in and the animals who share that environment,” she says. “We need to take the obvious step of addressing threats in any of these areas as an overarching, One Health problem.”
