US experts have issued reassurances that there is minimal risk of a bird flu outbreak among people, after a surge of infections among dairy herds in several states – and at least one case in a Texan farmworker – incited fears that the virus may be the world’s next infectious threat to populations.
The virus, H5N1, is highly pathogenic, and has the ability to cause severe disease and death. But while its spread among cows was unexpected, people can catch the virus only from close contact with infected animals, not from one another, officials said.
“It’s really about folks who are in environments where they may be interacting with cattle that are infected with this virus,” said Dr Demetre Daskalakis, director of the National Centre for Immunisation and Respiratory Diseases at the US Centres for Disease Control and Prevention.
“The risk for almost everyone else is very low,” he told The New York Times. “Right now, our risk assessment hasn’t changed, but if it does change, we’re going be quick and transparent about that.”
While avian influenza is often fatal in birds, none of the infected cows has died so far. The only symptom in the patient in Texas was conjunctivitis, or pink eye, which was also reported in people infected during other bird flu outbreaks.
The CDC and other agencies elsewhere have tracked H5N1 for years to monitor its evolution, and federal agencies have stockpiled vaccines and drugs to be used in a possible outbreak.
“We are more ready for an influenza pandemic than probably any other outbreak that could occur, any other pathogen,” said Rick Bright, chief executive of Bright Global Health, a consulting company focused on improving responses to public health emergencies.
Bright led influenza preparedness at the Biomedical Advanced Research and Development Authority (BARDA) which supports research on vaccines and drugs for emergencies, for several years before serving as the agency’s director from 2016 to 2020.
Is a human pandemic inevitable?
Among birds and animals, the H5N1 bird flu is already a pandemic, or a panzootic, with infections observed on every continent except Australia. To date, the virus has not evolved into a form that can spread easily from one person to another, and it may never do so.
It has primarily been a problem in birds. But it has now spread to a wide range of species, from sea birds and small scavengers like foxes to large mammals, like bears and cows.
There have been sporadic infections in people since 1997, when a cluster of cases appeared in Hong Kong. But most patients worldwide have been in very close contact with infected animals, and generally did not pass the virus to other people.
To become adept at transmission between people, H5N1 would need to pick up several additional mutations and shift its shape. The strain that was isolated from the infected farmworker in Texas carries one of those mutations, but that change has appeared before – in people, foxes and seals, among others – without further consequences.
“The infections in people so far fortunately are all still single-time cross-species transmission,” said Vincent Munster, a virologist at the National Institute of Allergy and Infectious Diseases who has studied the mutations needed for H5N1 to adapt to people.
History suggests that even if the virus changes enough to begin widespread transmission between people, it may have to give something up in return, Munster said. For example, when other flu viruses have adapted to humans, they have lost much of their virulence, causing only mild symptoms.
Do we have a vaccine for bird flu?
Yes. BARDA has enough building blocks for vaccines, including adjuvants – substances that can enhance a vaccine’s strength – to make millions of doses in weeks. Mass production could also ramp up quickly if needed, authorities said.
The CDC already has two candidate viruses that can be used to make vaccines. As the virus changes, gaining mutations that make it resistant to the current vaccines and drugs, for example, federal researchers may create newer candidates.
Three pharmaceutical companies can be called on to make vaccines for bird flu, but those would be manufactured on the same production lines used to make seasonal flu jabs.
Before embarking on large-scale manufacturing, authorities would have to consider the implications of disrupting seasonal production, said Dr David Boucher, the infectious disease director at the federal Administration for Strategic Preparedness and Response.
BARDA is also looking to add mRNA to the list of technologies that can be used to make bird flu vaccines.
At least four antiviral medications are available to treat people who may become infected, including the widely available generic drug oseltamivir, sometimes marketed as Tamiflu.
Unlike the vaccines, which are stockpiled by the government, the antiviral drugs are available commercially. Generic versions of oseltamivir are made by many manufacturers worldwide.
The government has a stockpile of tens of millions of doses of oseltamivir, Boucher said, and was in close communication with manufacturers that could quickly ramp up the production of oseltamivir, as it has in the past during some bad flu seasons.
All of these preparations are in place for a worst-case scenario, but “we’re not there yet”, he added. “Our job here is to prepare for the worst and get ready for it in case it does come.”
The New York Times article – Is Bird Flu Coming to People Next? Are We Ready? (Restricted access)
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American gets bird flu from infected cow
China reports first known death from H3N2-H10N5 flu co-infection
World’s first bird flu death recorded in China
Will bird flu spark the next pandemic?