According to leading scientists, influenza is the pathogen most likely to cause a new pandemic in the near future.
An international survey to be published this weekend will reveal that 57% of senior disease experts now believe a flu virus will be the cause of the next global outbreak of deadly infectious diseases.
The belief that flu is the world’s biggest pandemic threat is based on long-term research showing that it is constantly evolving and mutating, says Jon Salmanton-García of the University of Cologne, who conducted the study.
“Every winter flu happens,” he said. “You could describe these outbreaks as small pandemics. They are more or less controlled because the different strains that cause them are not virulent enough – but that won’t necessarily be the case forever.”
Details of the study – which involved a total of 187 senior scientists – will be unveiled next weekend at the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) congress in Barcelona.
The next most likely cause of a pandemic, after flu, is likely a virus – called Disease They believe the next pandemic will be caused by a yet-to-be-identified microorganism that will appear out of nowhere, just as the Sars-CoV-2 virus, the causative agent of Covid-19, did when it started killing people in 2019 infect.
Some scientists still believe Sars-CoV-2 remains a threat, with 15% of scientists polled in the study calling it the most likely cause of a pandemic in the near future.
Other deadly microorganisms – such as Lassa, Nipah, Ebola and Zika viruses – were considered serious global threats by only 1% to 2% of respondents. “Influenza remained very much the greatest threat in terms of pandemic potential in the eyes of a large majority of the world’s scientists,” Salmanton-García added.
Last week, the World Health Organization raised fears about the alarming spread of the H5N1 flu variant, which is causing millions of cases of bird flu worldwide. This outbreak started in 2020 and has resulted in the death or culling of tens of millions of poultry and has also wiped out millions of wild birds.
Recently, the virus has spread to mammal species, including domestic livestock, which are now infected in twelve US states, further increasing fears about the risks to humans. The more mammalian species the virus infects, the more chances it has to evolve into a species dangerous to humans, Daniel Goldhill of the Royal Veterinary College in Hatfield told the magazine Nature last week.
The appearance of the H5N1 virus in cattle was a surprise, says virologist Ed Hutchinson of the University of Glasgow. “Pigs can get bird flu, but until recently cattle could not. They were infected with their own strains of the disease. So the appearance of H5N1 in cows was a shock.
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“It means that the risks of the virus getting into more and more farm animals, and then from farm animals into people, are increasing. The more the virus spreads, the more likely it is to mutate so it can spread to people. In short, we are rolling the dice with this virus.”
To date, there is no evidence that H5N1 is spreading between humans. But in hundreds of cases where people have been infected through contact with animals over the past two decades, the impact has been grim. “The death rate is extremely high because people have no natural immunity to the virus,” said Jeremy Farrar, chief scientist at the World Health Organization.
The prospect of a flu pandemic is alarming, although scientists also point out that vaccines against many strains, including H5N1, have already been developed. “If there were an avian flu pandemic, it would still be a huge logistical challenge to produce vaccines at the scale and speed that will be needed. However, we would be much further along that path than with Covid-19, when a vaccine had to be developed from scratch,” Hutchinson said.
Nevertheless, some lessons about preventing the spread of disease have been forgotten since the end of the Covid pandemic, says Salmanton-García. “People are coughing into their hands again and then shaking hands with other people. Mask wearing is gone. We fall back into our old, bad habits. We might regret that.”