H5N1 has made the jump to livestock, appearing in herds across the US in recent weeks. Scientists believe the virus may pass from cow to cow, without relying on transmission from infected birds. There are reports of cats on farms becoming infected after drinking cow's milk, and one case of a human in the US contracting the disease after contact with livestock.
Dr. Richard Webby is an infectious disease researcher at Saint Jude's Children's Research Hospital in Memphis, Tennessee, and director of the World Health Organization's Collaborating Center for Influenza Studies.
He told RNZ Sunday morning The sudden jump of the virus in cows and its rapid spread surprised experts.
“It's almost like the Crusaders lose five in a row. Would you have asked me six weeks ago what the odds were? [was] If I had found this virus in cows, I wouldn't have said anything. So it is a completely new event for us.
“We think we know this virus, and then something happens next week that tells us we actually didn't know anything about it.”
Hundreds of human H5N1 cases have been reported since the virus was discovered in the late 1990s – about half of them fatal, making it potentially much deadlier than Covid-19 even before we had vaccines.
A recent international survey of senior disease experts found that 57 percent believe a flu strain will be the cause of the next global outbreak of deadly infectious diseases.
“Influenza is always at the top of the list,” Webby said. “We don't need to know exactly what the next agent is going to be, but you know, preparing for it could very well give us an edge. [in] prepare for the other.”
Although humans can be infected with H5N1, there is limited evidence of human-to-human transmission.
“It would still rather be in a replicating bird than anywhere else,” Webby said. “But every time it gets into a mammal, at least theoretically that gives that virus a little bit more opportunity to change and maybe become a little bit more mammalian, like a little bit more able to infect mammals, including humans.
“So from that perspective, every time we see it in a mammal it's concerning, but we're going into this a little bit blind right now, to be honest – we don't know what's likely to happen here. We don't know what the virus is going to do in terms of change.”
If it were to infect pigs, that would be a cause for greater concern.
'They have their own flu. Many of them are actually viruses that we humans have given them and managed to perpetuate.
“But if we look at what we know about the different hosts, we know that when these avian viruses get into pigs, the growth in the pig can actually make these viruses more contagious to humans. So yes, that's why we definitely shouldn't introduce this virus into want to have that host.”
We are unlikely to get advance warning from scientists if the disease were to spread among people, he warned.
'If the virological stars suddenly align and an avian virus in a cow suddenly one day acquires all the mutations it needs to be a human virus, then the chances of us picking that up in advance are quite slim . We will find that out when we start to see an accumulation of human cases.”
As for New Zealand's vast dairy industry, Webb said the risk was low – for now.
“I think if I was a cow in New Zealand I would honestly feel quite safe from this virus. If I were a chicken, I might feel a little less safe. But what I mean by that If this is an episode in cows, this is the first time we've seen this in the more than 25 years we've been following.
“The great-great-grandfather and grandmothers of this virus originated in Southeast Asia in the late 1990s. We have never seen it in cows before. So even though this virus has been around for so long, it has spread to cows, it has been quite rare.
“So put yourself in a New Zealand situation. If you're a cow in New Zealand, it's not just the fact that this virus doesn't seem to get into cows that much, it's that you don't even have the virus there. but so it's a pretty safe place to be.”
The Ministry for Primary Industries and the Department of Conservation have prepared a contingency plan for an inevitable bird flu “tsunami” coming to New Zealand. It has already been found in Antarctica.
There are some migratory birds that visit New Zealand.
“Just because New Zealand doesn't have it yet, I don't think, I wouldn't say that's going to be a true statement forever. But the chances of it, one, entering New Zealand and then two, it entering a New- Zeeland cow, I think the chance is quite small.”
Coming so soon into the world-changing Covid-19 pandemic, the largest of its kind in a century, Webby feared the public would not take the threat seriously. SARS-CoV-2 – the virus behind Covid-19 – made the jump from an animal host to humans sometime in late 2019, scientists think.
“This is a bad time for this to happen – 'It's those scientists again, they're going to worry about a virus that's going to come and kill us all tomorrow:' …People don't want to hear about this.
'They don't want to hear that they have been vaccinated again against a new virus. So yes, [the] The timing is certainly not good.”
If an outbreak were to occur in humans, Webby also feared that – despite the lessons learned from Covid-19 – officials would not be ready.
“Maybe it's not this virus, but something is definitely going to do that. It's going to jump from an animal to humans and we're going to have another Covid pandemic, or it could also be some kind of supercharged Covid pandemic. .
“There's clearly not enough resources going into this pandemic preparedness, and that's not a New Zealand-centric issue, not a US-centric issue, but a global issue. You know, it's almost like we're not willing to kind of put those resources into the insurance that we really need.”