The avian flu virus spreading among wild birds, poultry, and mammals could lead to a pandemic worse than COVID-19 if it mutates so that it can be transmitted from human to human, the head of the Pasteur Institute’s respiratory infections centre said today.

Bird flu has led to the slaughter of hundreds of millions of birds in recent years, disrupting food supplies and causing prices to rise, although human infections remain rare.

Capable of human-to-human transmission

“What we fear is that the virus will adapt to mammals, particularly humans, and thus become capable of human-to-human transmission, and that the virus will be a pandemic virus,” Marie-Ann Rame Veltie, medical director of the Pasteur Institute’s respiratory infections centre, told Reuters.

The Pasteur Institute was among the first European laboratories to develop and share COVID-19 detection tests, making the protocols available to the World Health Organization and laboratories around the world.

Humans have antibodies to common seasonal influenza H1 and H3, but not to avian influenza H5, which affects birds and mammals, just as they did not have antibodies to COVID-19, he said.

And, unlike what happens with COVID-19, which mostly affects vulnerable groups of people, flu viruses can also kill healthy people, including children, Rame-Velti said.

More serious than the pandemic we’ve been experiencing

“A bird flu pandemic would probably be quite severe, possibly even more severe than the pandemic we experienced,” she said from her lab in Paris.

There have been many cases of people infected with H5 avian flu viruses in the past, including the H5N1 currently circulating among poultry and dairy cows in the US, but these have usually been in close contact with infected animals. A first-ever case of a human infected with H5N5 was recorded in the US state of Washington this month. The man, who had underlying medical conditions, died last week.

In its most recent report on bird flu, the World Health Organization said there have been nearly 1,000 human outbreaks between 2003 and 2025 — mostly in Egypt, Indonesia, and Vietnam, 48 percent of whom died.

However, the risk of a human pandemic developing remains low, Gregorio Torres, head of the World Organisation for Animal Health’s science department, told Reuters.

We need to prepare

“We need to prepare to respond in a timely enough manner. But for now you can walk comfortably in the forest, eat chicken and eggs, and enjoy life. The risk of a pandemic is a possibility. But as a possibility, it’s still very low,” he said.

Rame-Velti also said that in the event that bird flu could mutate so that it could be transmitted from human to human, the world today is better prepared than it was before the COVID-19 pandemic.

“The positive point with influenza, compared to COVID, is that we have put in place specific preventive measures. ‘We have vaccine candidates ready, and we know how to prepare a vaccine quickly,’ he said.

‘We also have stocks of specific antivirals that, in principle, will be effective against this avian influenza virus,’ he added.