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This week marks a strange anniversary—it’s five years since most of us first heard about a virus causing a mysterious “pneumonia.” A virus that we later learned could cause a disease called covid-19. A virus that swept the globe and has since been reported to have been responsible for over 7 million deaths—and counting.
I first covered the virus in an article published on January 7, 2020, which had the headline “Doctors scramble to identify mysterious illness emerging in China.” For that article, and many others that followed it, I spoke to people who were experts on viruses, infectious disease, and epidemiology. Frequently, their answers to my questions about the virus, how it might spread, and the risks of a pandemic were the same: “We don’t know.”
We are facing the same uncertainty now with H5N1, the virus commonly known as bird flu. This virus has been decimating bird populations for years, and now a variant is rapidly spreading among dairy cattle in the US. We know it can cause severe disease in animals, and we know it can pass from animals to people who are in close contact with them. As of this Monday this week, we also know that it can cause severe disease in people—a 65-year-old man in Louisiana became the first person in the US to die from an H5N1 infection.
Scientists are increasingly concerned about a potential bird flu pandemic. The question is, given all the enduring uncertainty around the virus, what should we be doing now to prepare for the possibility? Can stockpiled vaccines save us? And, importantly, have we learned any lessons from a covid pandemic that still hasn’t entirely fizzled out?
Part of the challenge here is that it is impossible to predict how H5N1 will evolve.
A variant of the virus caused disease in people in 1997, when there was a small but deadly outbreak in Hong Kong. Eighteen people had confirmed diagnoses, and six of them died. Since then, there have been sporadic cases around the world—but no large outbreaks.
As far as H5N1 is concerned, we’ve been relatively lucky, says Ali Khan, dean of the college of public health at the University of Nebraska. “Influenza presents the greatest infectious-disease pandemic threat to humans, period,” says Khan. The 1918 flu pandemic was caused by a type of influenza virus called H1N1 that appears to have jumped from birds to people. It is thought to have infected a third of the world’s population, and to have been responsible for around 50 million deaths.
Another H1N1 virus was responsible for the 2009 “swine flu” pandemic. That virus hit younger people hardest, as they were less likely to have been exposed to similar variants and thus had much less immunity. It was responsible for somewhere between 151,700 and 575,400 deaths that year.
To cause a pandemic, the H5N1 variants currently circulating in birds and dairy cattle in the US would need to undergo genetic changes that allow them to spread more easily from animals to people, spread more easily between people, and become more deadly in people. Unfortunately, we know from experience that viruses need only a few such changes to become more easily transmissible.
And with each and every infection, the risk that a virus will acquire these dangerous genetic changes increases. Once a virus infects a host, it can evolve and swap chunks of genetic code with any other viruses that might also be infecting that host, whether it’s a bird, a pig, a cow, or a person. “It’s a big gambling game,” says Marion Koopmans, a virologist at the Erasmus University Medical Center in Rotterdam, the Netherlands. “And the gambling is going on at too large a scale for comfort.”
There are ways to improve our odds. For the best chance at preventing another pandemic, we need to get a handle on, and limit, the spread of the virus. Here, the US could have done a better job at limiting the spread in dairy cows, says Khan. “It should have been found a lot earlier,” he says. “There should have been more aggressive measures to prevent transmission, to recognize what disease looks like within our communities, and to protect workers.”
States could also have done better at testing farm workers for infection, says Koopmans. “I’m surprised that I haven’t heard of an effort to eradicate it from cattle,” she adds. “A country like the US should be able to do that.”
The good news is that there are already systems in place for tracking the general spread of flu in people. The World Health Organization’s Global Influenza Surveillance and Response System collects and analyzes samples of viruses collected from countries around the world. It allows the organization to make recommendations about seasonal flu vaccines and also helps scientists track the spread of various flu variants. That’s something we didn’t have for the covid-19 virus when it first took off.
We are also better placed to make vaccines. Some countries, including the US, are already stockpiling vaccines that should be at least somewhat effective against H5N1 (although it is difficult to predict exactly how effective they will be against some future variant). The US Administration for Strategic Preparedness and Response plans to have “up to 10 million doses of prefilled syringes and multidose vials” prepared by the end of March, according to an email from a representative.
We can’t predict how well these viruses will work, either. Flu viruses mutate all the time, and even seasonal flu vaccines are notoriously unpredictable in their efficacy. “I think we’ve become a little bit spoiled with the covid vaccines,” says Koopmans. “We were really, really lucky [to develop] vaccines with high efficacy.”
One vaccine lesson we should have learned from the covid-19 pandemic is the importance of equitable access to vaccines around the world. Unfortunately, it’s unlikely that we have. “It is doubtful that low-income countries will have early access to [a pandemic influenza] vaccine unless the world takes action,” Nicole Lurie of the Coalition for Epidemic Preparedness Innovations (CEPI) said in a recent interview for Gavi, a public-private alliance for vaccine equity.
And another is the impact of vaccine hesitancy. Making vaccines might not be a problem—but convincing people to take them might be, says Khan. “We have an incoming administration that has lots of vaccine hesitancy,” he points out. “So while we may end up having … vaccines available, it’s not very clear to me if we have the political and social will to actually implement good public health measures.”
This is another outcome that is impossible to predict, and I won’t attempt to do so. But I am hoping that the relevant administrations will step up our defenses. And that this will be enough to prevent another devastating pandemic.
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