The World Health Organisation has warned that a new variant of the influenza virus is rapidly gaining ground, but expressed hope that vaccination remains the “most effective defence”.

Wenqing Zhang, unit head for global respiratory threats at the Department of Epidemic and Pandemic Threats Management of WHO, told reporters in Geneva.

Mr Zhang noted that this year is marked by “the emergence and the rapid expansion of a new AH3N2 virus subclade”.

“The new variant – called J.2.4.1 or subclade K – was first noted in August in Australia and New Zealand and has since been detected in over 30 countries.

“Current epidemiological data do not indicate an increase in disease severity, although this genetic shift makes a notable evolution in the virus,” Ms Zhang said.

Influenza viruses are constantly evolving, she explained, which is why the composition of the influenza vaccine is regularly updated.

“WHO tracks these changes, assesses associated risks to public health and makes vaccine composition recommendations twice a year through a longstanding global system – the Global Influenza Surveillance and Response System (GISRS) – in collaboration with other global experts.

“The new variant has not been incorporated and is not part of the composition of the latest vaccines produced for the Northern Hemisphere influenza season,” the WHO expert explained.

“Early evidence suggests that current seasonal vaccines continue to offer protection against severe diseases and reduce the risk of hospitalisation,” she said.

WHO estimated that there are around one billion cases of seasonal influenza annually, including up to five million cases of severe respiratory illness.

It added that up to 650,000 deaths each year are due to seasonal influenza-related respiratory disease.

“Vaccination remains our most effective defence, including against drifted strains, particularly for high-risk populations and those taking care of them,” Ms Zhang insisted.

The WHO expert shared the results of an early estimate of the vaccine’s effectiveness against the new variant, published in the United Kingdom a few weeks ago.

“It’s quite promising,” she said, pointing to the data which showed that the vaccine is around 75 per cent effective against severe disease and hospitalisation in children and around 35 per cent among adults.

She warned that the upcoming holiday season may bring a further surge in respiratory illnesses.

“Advanced planning and preparedness efforts, including encouraging vaccination uptake and strengthening health system readiness, are strongly recommended,” she said.

The WHO expert advised countries to strengthen lab diagnostics and year‑round disease surveillance and to participate in the WHO GISRS surveillance network.

The network comprises influenza centres in 130 countries and a dozen reference laboratories.

Asked about whether the United States will remain a member of the network next year, despite the country’s decision to leave the WHO, effective January 22, 2026, Ms Zhang noted that global collaboration is key, saying every country is crucial for flu surveillance, preparedness, and response – for influenza and other respiratory viruses, worldwide participation is a must.

“Because we don’t know the next pandemic strain or when and where it will emerge. And that time between the emergence and being picked up and characterised and put into vaccines would make a lot of difference with regard to the number of lives that could be saved,” she said.

(NAN)