I’ve been writing about the growing risk of a pandemic H5N1 bird flu for several years and I can’t help feeling that the virus is surrounding us in order to figure us out.
It has already infected tens of millions of birds around the world, has become a transmissible viral vector among mammals, including mink, domestic cats, marine mammals and now cows, with virus particles polluting the milk supply.
As the virus increases its range and target hosts, it is a giant step closer to figuring out how to become a human viral infection spread via respiratory droplets as with other influenza viruses with potentially devastating consequences.
Only two human cases have so far been reported. But we must see this as a clear signal that the virus can jump to the human species (eg, zoonotic) and it’s not just happening in Southeast Asia anymore. The H5N1 outbreak has spread to cows on 34 dairy farms in nine states and it’s likely that the virus was spreading among cows for months before it was detected.
The concern is that this rapidly mutating virus has now arrived at an important inflection point of human-animal convergence.
From 2003 to July 2023, the World Health Organization documented 878 cases of bird flu infection in humans and 458 (52.16%) fatalities in 23 countries. And while it’s true that we don’t really know the total number of people who were infected worldwide and who survived without being reported (eg, the true epidemiological denominator), thereby lowering the actual mortality rate, do we really want to take the chance?
While bird flu does not yet easily jump to humans, we need to remember that highly pathogenic H5N1, at its core, is an influenza virus which, in its influenza form, figured out how to become a transmittable human virus a millennium ago.
FDA Commissioner Robert Califf testified to Congress this month about the risk of a pandemic bird flu in humans and warned of a predicted mortality rate of 25% in the event of an H5N1 pandemic. To put this into perspective, SARS CoV-2 virus killed approximately 1% of its human targets around the world, and we’ve all seen the profound global impact on morbidity and mortality that has had, along with the devastating economic toll.
A viral bird flu pandemic in humans with a mortality rate as high or higher than COVID-19 would be a catastrophic global event, so it’s time to start worrying and start taking action.
But how, you may wonder, could a virus that infects primarily birds become a global pandemic in humans? Viruses constantly undergo rapid genetic reassortment and mutation which makes them remarkably versatile survivors. It’s what also makes them very dangerous. Pigs have long been considered potential intermediate hosts in which avian influenza viruses can adapt to humans.
Here’s how this might work: co-infection with both the influenza A virus and the avian H5N1 virus in pigs could reassort and combine to create a new virus mutation with genes from the avian H5N1 bird flu virus and genes from the influenza A virus. Pig-to-pig transmission of this highly pathogenic mutated influenza A/avian bird flu virus would likely prolong the duration of virus infection within a pig population, thereby increasing the likelihood of adaptation and the subsequent generation of influenza A (H5N1) viruses that replicate efficiently and spread in humans. Such viral mutations could create viruses against which humans have little or no immunity that are more likely to result in sustained human-to-human transmission.
Therefore, careful evaluation of influenza A viruses recovered from pigs or humans who are co-infected with avian influenza A and H5N1 viruses is very important to identify if such worrisome reassortment occurs.
What are we doing about it and what can be done in the future? The CDC recommends seasonal influenza vaccination to reduce the potential for co-infection with seasonal flu and bird flu to reduce chances of producing a highly pathogenic human-transmissible virus. CDC also recommends treatment as soon as possible with influenza antiviral drugs (eg, Tamiflu, Relenza) for people with suspected or confirmed influenza A(H5N1) virus infections.
The U.S. Department of Health and Human Services (HHS) Strategic National Stockpile program is now storing millions of doses of antiviral drugs strategically dispersed around the country in preparation of a bird flu pandemic in humans. At least three existing candidate vaccines could be used to rapidly scale up mass production of human vaccines against this virus if needed, including an mRNA vaccine option that could quickly ramp up production for tens of millions of doses.
The good news here (if any) is that we seem to be paying more attention to this potential viral pandemic at all levels of government and industry and that may be enough to avoid the next global viral pandemic.
David Segarnick is chief medical officer at MedEvoke, an iNIZIO company, and an adjunct assistant professor of pharmacology, physiology and neuroscience at Rutgers/NJ Medical School. He lives in Upper Black Eddy.
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