Bird flu has jumped across to cows and is rapidly spreading through herds in the United States — and scientists are worried.
Only four years since the start of the Covid pandemic, the unprecedented spread of a new strain of H5N1, or bird flu, among dairy cows in the U.S. is a reminder of our vulnerability to novel viral threats.
Jeremy Farrar, the World Health Organization’s (WHO) chief scientist, said last week the risk of spillover to humans from the new strain was an “enormous concern.” Bird flu rarely infects humans but is often fatal when it does. According to the WHO, the case fatality rate among humans since 2003 stands at 52 percent.
So just how worried should we be about this new type of bird flu in cows? POLITICO walks you through the main questions.
Why are scientists so worried?
The fact that the virus has turned up in mammals such as cows suggests the virus has mutated and brings it one step closer to infecting humans.
Avian flu has been seen as a pandemic risk for decades but, as the name suggests, it has mainly affected birds.
“The news confirms the capacity of flu to surprise us,” Paul Digard, a professor of virology and influenza specialist at the University of Edinburgh, told POLITICO. “Historically, we saw cows as being very low-risk for flu A (a subset of flu that causes sickness in humans and includes the virus now spreading in cattle). It ups the threat assessment a notch,” Digard added.
How widespread is the new strain?
It’s likely wider than previously reported.
“I believe the spread of infection will be far greater than the number of farms that’s been reported,” said James Wood, head of the department of veterinary medicine at the University of Cambridge.
The detection of viral RNA in milk indicates the disease is more widespread than previously thought, Wood explained.
As of Thursday in the U.S., around one in five retail milk samples tested positive for viral fragments.
Is this milk safe to drink?
Viral particles have been detected in commercial milk in the U.S. but that doesn’t necessarily mean it’s unsafe to drink. Pasteurization is effective at killing influenza and U.S. authorities have said there is no evidence the RNA particles detected in milk are able to infect anyone.
U.S. federal agencies (USDA, USFDA, CDC) have reiterated that “the commercial milk supply is safe.”
They also add that pasteurization is “likely” to inactivate the avian flu virus in milk while acknowledging that “no studies on the effects of pasteurization on [highly pathogenic avian influenza] viruses (such as H5N1) in bovine milk have previously been completed.”
The detection of viral RNA in U.S. milk probably isn’t of much concern for Europe. EU imports of milk from the U.S. are “very close to zero” and “statistically insignificant in terms of trade,” an EU official told POLITICO.
What’s the risk of the new strain to humans?
So far, the risk to people is limited, but there’s a lot we don’t know about the strain since it is so new.
There has been at least one human case of the new strain but there is no evidence of human-to-human transmission, a key pandemic threat marker.
The danger is that the virus mutates further and eventually develops the ability to infect humans more easily. The more widespread the virus is among animals, the more opportunities it has to do exactly that.
Has the new strain been detected in Europe?
At the moment, EU countries are watching developments closely.
“The infections of dairy cattle in the U.S. are with a strain of H5N1 that has not been detected in Europe. We are closely monitoring the situation and its possible evolution,” a spokesperson for the European Food Safety Authority (EFSA) told POLITICO.
A spokesperson for the European Commission added that it was carefully tracking any genetic evolution of the virus but that the threat to human health remained low for the general public.
Digard, meanwhile, says it would be wise to check dairy herds in the U.K. for the new strain even though there’s no evidence yet it has escaped North America.
In the EU, EFSA has advised increased surveillance in mammals, especially in those near bird flu-affected poultry establishments.
Do we have vaccines against bird flu?
There are vaccines that could work against bird flu, but it’s still unclear how effective they would be versus a particular strain and how quickly companies could ramp up production.
A GSK spokesperson told POLITICO the company has a contract with the EU’s Health Emergency Preparedness and Response Authority to produce 85 million doses of its pandemic preparedness vaccine, Adjupanrix, if needed. Adjupanrix is a “mock-up” flu vaccine that could be adapted to whatever influenza strain emerges as the cause of a pandemic.
A spokesperson for the European Commission, meanwhile, confirmed it had a joint contract with GSK and CSL Seqirus for the companies to deliver adapted flu vaccines if needed in a pandemic.
Andrew Fenwick, a spokesperson for CSL Seqirus, told POLITICO that the company’s zoonotic flu vaccine would likely protect against the strain currently circulating in the U.S.
The European Medicines Agency has also approved AstraZeneca’s pandemic flu vaccine, which was tested using a strain of H5N1.
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