France’s Institut Pasteur warns that highly pathogenic avian influenza (bird flu) could spark a pandemic worse than COVID-19 if the virus mutates to enable sustained human-to-human transmission, underscoring the gravity of adaptation to mammals and humans.

Marie-Anne Rameix-Welti, medical director at Pasteur’s respiratory infections centre, cautions that adaptation to mammals and humans could drive a severely impactful bird flu pandemic given the lack of existing human immunity.

Experts warn that a mammal-adapted H5 virus could cause a pandemic more severe than COVID-19 due to minimal human immunity and the potential for rapid spread.

The coverage places avian influenza in the broader context of zoonotic diseases and emphasizes the need for proactive, data-driven public health responses to emerging threats.

Health authorities stress that there is no crisis yet, but conditions for one exist as the virus spreads among animals, increasing the chance of future sustained human transmission.

Despite low current pandemic probability, preparedness is essential, including early response plans, ready vaccine candidates, rapid manufacturing capability, and antiviral stockpiles.

Gregorio Torres of the World Organisation for Animal Health says the risk of a human-to-human influenza pandemic remains low and notes the world is better prepared than during COVID-19, with vaccines and antivirals available.

Absence of antibodies to H5 in humans underscores potential susceptibility relative to common flu strains.

Scientists recognize that influenza can jump across species, enabling faster evolution and necessitating vigilant surveillance unlike the more contained spread of some other viruses.

Human infections have been reported across the Americas and Southeast Asia, but without sustained human-to-human transmission; the key concern remains mammalian adaptation enabling such transmission.

The article notes advantages over COVID-19: existing vaccine candidates, antivirals, and stockpiles that could be effective against avian influenza.

Past human infections with H5 have mostly occurred through close contact with infected animals; the first human case of H5N5 in Washington state this month resulted in death.

Bird flu has caused widespread culling and disruption of food supplies, while human infections remain rare so far.

The current H5 strain has infected birds and some mammals, with human infections being rare and most past cases linked to contact with infected animals.

There are currently no human antibodies against the H5 bird flu strain, unlike seasonal flu antibodies, highlighting vulnerability to spillover.

The warnings come amid concerns about animal reservoirs of avian influenza that could spill over to humans, posing a severe public health threat.

Two and a half years of H5 circulation in wild birds have driven outbreaks in poultry and mammals, raising concerns about increased human exposure.

Pasteur has a historical role in Covid-19 detection and is actively monitoring H5 evolution, developing vaccine prototypes, and assisting global detection using its pandemic response experience.

The institute is leveraging its Covid-19 response expertise to monitor H5, test vaccines, and support global detection efforts.

World Health Organization data show nearly 1,000 human outbreaks since 2003 with about 48% mortality, highlighting the ongoing risk of avian influenza.

WHO figures emphasize the severity potential of zoonotic spillover given the historical mortality burden linked to avian influenza.”},{