New virus appears in China

A new, previously-undocumented viral infection has broken out in China’s Wuhan City. So far, since early December when the first cases were picked up, about 60 people have developed the disease, some of them becoming severely unwell with respiratory symptoms. Scientists studying samples collected from patients showing signs of the infection have just announced that the new agent appears to be a member of a viral family called coronaviruses. Details of the new agent are still very sketchy. Chris Smith asked Cambridge University virologist AJ te Velthuis how this new infection could have appeared, and what might happen next, and then spoke with Freya Jephcott, also at the University of Cambridge. She models how disease outbreaks spread and was a consultant during the Ebola outbreaks in West Africa. She’s been looking at the latest updates from Wuhan City...

AJ - Going by previous outbreaks, these new viruses often emerge at animal markets, where different animals come together and viruses are able to spread from animal to animal, and then if humans visit those markets, those viruses can also spread to humans. In these cases you have domestic livestock which have been bred in high densities, and particularly those high densities allow the virus to spread very quickly and evolve and mutate more quickly as well.

Chris - Is this what we think happened with SARS back in 2003?

AJ - So in the case for SARS, we have a lot of evidence that allowed us to trace back where the SARS came from even from which market, and yeah, we were able to tell did it jump over from bats and from civet cats to humans at a particular market.

Chris - The mechanism then is you take an animal that we wouldn't normally spend much time rubbing up against like a bat, you put that in a market where there's an animal there next to it that's more similar to us than a bat is, and it can get into us via that other animal.

AJ - That's absolutely true. And this is also what we see in the case for avian influenza. It is quite hard for those viruses to spread between humans. But if you allow this virus to jump over to pigs and it can adapt, it has a much easier jump to humans.

Chris - So far, have they actually got any clues as to what this is?

AJ - At the moment they're ruling out avian influenza virus and SARS, but it could still be mutants of those particular viruses, and at present pretty much all cards are on the table.

Chris - So how do they gauge the threat and how do they minimise the risk?

AJ - To minimise the risk, the best strategy is to put people in quarantine, and monitor family members that the patients have been in contact with, and also to estimate if there is people to people, transmission. It is also important to notify the international community so airports can monitor people and see if someone is traveling with high fever.

Chris - So in terms of how we actually may manage outbreaks like this, what is now most likely happening in terms of investigating, probing the origin and following up both the people, and possibly the animals, that may have caused this?

AJ - So the markets have been closed down and they're being cleaned. People have been put in quarantine and samples have been taken and they're most likely sequenced now to figure out if there is a particular new virus present and whether we can relate to those sequences to known pathogens, and identify the virus better.

Chris - Are we comfortable that there isn't a threat to other people at this stage though?

AJ - Given that the virus is not spreading from human to human, the danger is better, simply limited. It is still okay to go to China. But you'ew strongly advised not to visit any animal markets right now.

Adam - Thanks to AJ te Velthuis, Freya, Jephcott is also at the University of Cambridge. She models how disease outbreaks spread and was a consultant during the Ebola outbreak in West Africa. She has been looking at the latest updates from Wu Han city.

Freya - Right now, it's unclear what's causing the current outbreak in Wu Han, from reports coming from the local officials, it sounds like they're fairly certain they're dealing with a virus, and it sounds like they've eliminated most, if not all of the common causes of viral pneumonia, as well as some of the rarer ones too like SARS, coronavirus and avian influenza. Since Wednesday, there have been some reports circulating that a novel previously unseen coronavirus was detected in one or more of the patients. In the past, coronaviruses like SARS and MERS have made the leap from animals into humans, and in the case of that 2002 SARS epidemic, it looks like that leap took place in a live animal market, much like the one implicated in the current Wu Han outbreak.

Even if it turns out that this is the case, there's still a lot more questions that need answering. What animal did it spill over from? Is this virus transmissible between people? Could it become transmissible between people once the virus has had a chance to adapt to its new human hosts? At present, there's still too little information available to ascertain what the true public health significance of this event is. Viruses are constantly spilling over from animal populations into human ones and only a very small proportion of these is capable of causing disease in humans. And an even smaller proportion of those is capable of causing a disease transmissible between people. That said, in an increasingly interconnected and densely populated world and with a respiratory illness, there is reason to be wary.