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The US must strengthen measures to control the country’s bird flu outbreak and curb the growing risk that the virus will evolve to spread more easily between humans, international health experts have warned.
Scientists have called for increased vaccination of farm workers and more efforts to stem the spread among farm animals as the H5N1 pathogen continues to infect cattle and chickens across the country.
The epidemic is an early test for President Donald Trump’s administration, which is already scaling back commitments to global efforts on disease control and prevention.
“It is arguably grossly irresponsible for the US authorities to allow such sustained high level of virus transmission in dairy cattle as this poses such a major threat to global human health,” said Professor James Wood, an infectious diseases expert at the UK’s Cambridge university.
He added that curbs such as stricter movement of cattle “would hugely reduce human exposure and would be expected in every other country”.
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Experts have watched with growing alarm as H5N1 has circulated in the US for more than nine months. The outbreak has resulted in 67 confirmed human cases, mostly in people who work with cattle and chickens, according to the US Centers for Disease Control and Prevention.
The first fatality was reported this month, although no cases of human to human transmission have yet been documented.
Virologists fear a reassortment of genetic material from the H5N1 pathogen with another animal or human flu, creating a new virus that is more likely to be transmitted between people. The possibility of this scenario rises as H5N1 circulates in the US during the winter flu season.
There were an estimated 12mn-22mn human flu cases between October 1 and January 11, according to the CDC. On January 16, it urged hospitals to analyse within 24 hours whether flu sufferers actually contracted bird flu, particularly if patients were in intensive care. The CDC said in November it had provided human flu vaccines to farm workers in 12 states.
It considered H5N1’s risk to the public to be low, but added that it was “closely monitoring this dynamic situation”.
The World Organisation for Animal Health, the UN Food and Agriculture Organization and the World Health Organization have said governments should step up several measures to combat the spread of bird flu. These include strengthening virus testing, sequencing and data sharing, improving farm biosecurity and protecting people who were exposed to infected animals, said Maria Van Kerkhove, a top WHO official.
“More can and should be done to reduce the spread of avian influenza in animals, between different animal species and to humans,” said Van Kerkhove, who is acting director of pandemic preparedness.
The WHO also encouraged pharmaceutical companies to develop more animal vaccines that can be widely used to reduce the spread of bird flu, Van Kerkhove added.
The three leading makers of bird flu vaccines for humans — CSL Seqirus, Sanofi and GSK — are well placed to respond if the outbreak becomes a pandemic. In October, the trio signed a $72mn agreement with the US government that included commitments to prepare to distribute doses quickly and sustain supply levels.
The US government on January 17 gave $590mn to Moderna, which is developing a flu vaccine using similar messenger RNA-based technology as its Covid jab.
The Seqirus jab has been ordered by many European governments but Finland is the only one to have confirmed it is using the vaccines to inoculate farmworkers. The vaccine maker said the Nordic country was also conducting its own independent study on the jab’s safety and efficacy.
The US response to bird flu has been further complicated by a “short pause” placed on “mass communications and public appearances that are not directly related to emergencies or critical to preserving health” by the health and human services department and other bodies.
The Trump administration initiated the pause to “set up a process for review and prioritisation”, the health department said.
Trump and his allies are critical of fundamental aspects of international disease control, while Robert F Kennedy Jr, his nominee for health and human services secretary, is a long-standing vaccine sceptic.
One of Trump’s first actions after his inauguration was to trigger the year-long process to pull the US out of the WHO. He took the same action in 2020 during his previous term, but president Joe Biden reversed the decision on taking office in January 2021.
Data visualisation by Bob Haslett