New swine flu strain confirmed in the UK

Health officials are investigating the first confirmed case of a new strain of swine flu in the UK. The A(H1N2)v infection was detected in a routine flu screening test at a GP surgery in North Yorkshire. Health protection teams are currently investigating, so what do we know so far? Chris Smith put in a call to one of the UK’s leading experts on flu viruses...

Ed - I'm Ed Hutchinson. I'm a virologist at the MRC University of Glasgow Centre for Virus Research. Influenza grows in lots of different types of animals and humans are just one of them. And viruses more than any other infectious disease really have an intimate relationship with their hosts. They're trying to take them over, make them into factories for making more viruses, and that means they have to be really good at growing in one particular host species only. That means that when you catch influenza, you've normally caught it off another human who has an influenza in them, which is good at growing in humans. Very occasionally, a virus can get from one species and infect another species. So if a virus from a pig gets into a human, it might infect the human causing what we call a spillover infection. And that may or may not make the person sick, but it's unlikely to replicate enough to go further. What seems to have happened in this particular case is that someone has been infected with an influenza virus from pigs. They developed a fairly mild illness and thankfully they apparently have fully recovered from that. But whilst they're ill, they went to their GP and they were swabbed. So this is an example of a virus which has jumped into a human. What we don't yet know is whether it's going to be good at jumping from a human into other humans. Most of the time, viruses from animals are not good at jumping from humans into other humans. Very occasionally they do get better at it, and that would be a concerning situation. So that's what people are now closely monitoring to try and work out whether there's any evidence of those further jumps from humans to humans happening.

Chris - Can the genetic code tell us anything? When Covid was rampaging around the planet, there was enormous effort, energy, and investment put into reading its genetics, and that was revealing about a lot about where these viruses were coming from, how they were evolving and so on. Can we do the same for this flu case?

Ed - Absolutely, and for two ways in which we can do it. The first is to figure out where this virus has come from. And the way we do that is basically to build a family tree of the virus. Just like your genes are going to be more similar to those in your immediate family than to people who are only distantly related to, the genes of viruses in swine are more closely related to those of other pig viruses than to human viruses. The other thing we can do is we can look for genetic changes in the virus which suggests that it might be adapting and getting better to growing humans. And influenza is unusual in among viruses in that it can quite readily swap some of its genes between viruses. They get into the same cell, they can breed with each other. So although there's no evidence of this happening yet we'd be particularly concerned if we saw any evidence that one of these swine viruses, which has jumped into humans, has started to swap genes with the human viruses already in humans 'cause that that could accelerate a virus getting used to growing in humans.

Chris - Indeed, it is human flu season right now, isn't it? So that, I suppose the odds of that happening are higher. What would be the implications of that if we did end up with a baby virus that had the best of both, it looked like this pig virus, but had the ability to grow and spread well, like a human flu virus? What would be the implication?

Ed - So the reason people are monitoring this very carefully is that the worst case scenario - and, to be clear, there's no evidence yet that we are there or heading that direction - but the worst case scenario is that you have a new human virus and a new human virus will cause a pandemic. So by paying close attention to this now, we can figure out what's going on. We can trace contact to people who may have been exposed to virus, if there is a virus that's spreading, and make sure it doesn't spread further.

Chris - So how will the public health team who are looking into this case be pursuing it? What will be their main priorities and what are they gonna be hoping to learn or reassure themselves of?

Ed - So I think the three main questions are how did this virus get from a pig into a human? Because this is not something you can get from eating pork, for example, this is a respiratory virus, so you have to be fairly close to a a pig, which is snuffling away. So it needs to be clear how that transmission takes place. It needs to be clear whether anyone else particularly in the area has also picked up viruses related to this or whether this is really just an isolated case. And it needs to be established whether any of the contacts of this person have the infection as well. So is there any evidence of transmission, not just from a pig to a human, but from human to human transmission? Hopefully what we'll find is this was just an isolated one-off case. But if we find that the virus is infecting a number of people or even spreading between people, then it will be important to try and make sure that it doesn't spread any further than it already has.