Coronavirus

A new and deadly strain of virus thought to have originated from contact with infected animals in the middle east is raising concerns as evidence mounts that it can also pass from human to human.  To find out more, we spoke to Professor Wendy Barclay who is Chair in influenza virology at Imperial College London.

Ben - First of all, what is this virus?

Wendy -   Well, this virus is a coronavirus, but a virus in quite a large family that includes viruses of both humans and animals.  The name suggests that it's got a special appearance.  It's got some spike-like proteins on the outside which under the electron microscope look a little bit like crowns.  Hence, the corona and the virus is carrying inside it an RNA genome which of course we know makes viruses a little bit more mutable than viruses which rely on DNA for their genome.  Coronaviruses are quite notorious in the RNA-genomed viruses as being extremely large.  They have really  the largest RNA genome of maybe up 30 kilobases in length which is large for a single piece of RNA.  Until sort of around about 2002, 2003, the only coronaviruses that people knew about that infected human beings were two rather mild corona viruses that caused common colds.  And then of course along in 2003, came SARS coronavirus which hit the scene and made everybody sit up and realise that these coronaviruses could also cause much more serious disease, and that again seems to be what we're seeing here this time around as well.

Ben -   So, how does this coronavirus then and this particular strain differ from other respiratory infections like influenza?

Wendy -   Well, in many ways, there are some similar features.  Particularly with severe forms of influenza, for example, the H5N1 bird flu when it does infect humans, causes a very severe lung involvement, viral pneumonia, severe respiratory illness, and that seems to be so far what's being seen in these 11 people now that appear to have been infected with the new coronavirus.  So, there are some similarities there.  Indeed, it could be said really that SARS was also a virus which causes a sort of very much a lower respiratory infection.  That differs is I guess from typical common colds and most strains of seasonal flu which although there can be lung involvement really, are also infecting the upper respiratory tract and passing amongst people quite readily through the air.

Ben -   You said we've had 11 confirmed cases of this so far, so it obviously is quite a new strain.  Where do you think it's actually come from?

Wendy -   So, genome sequencing suggests that this is really highly related to viruses which are found in bats. Again, since the SARS epidemic, a lot of work has been done on coronaviruses and looking for new viruses because we think that SARS in fact came originally from bats, although it seems that SARS went through other animals first to sort of adapt and allow it to cross that species barrier and get into humans.  This virus actually seems much more similar to viruses which are in bats, suggesting that it may not have gone through an intermediate animal species, but may have come directly across from bats into humans.  But to be honest, the animal source of the infection which most have originated in Saudi Arabia, the animal source of these infections really is not identified.

Ben -   And this has been making the headlines primarily because it seems to have been able to go not just from bats to humans but actually, from one infected human to another.  Why is that such a concern?

Wendy -   Well, when we have these viruses that are usually present in animals and it cross once into an exposed person, we call that a zoonosis.  And although that's very unfortunate for the infected person because often, that's accompanied by severe disease, it doesn't necessary trigger an outbreak.  A lot of animal viruses can, following a big dose exposure can cause this zoonotic event, but when we get really worried is when there are new viruses which cross from an animal species and they have the capability to pass from one person to another.  Now, I should stress that although this corona virus have hit the headlines because it appears to have done that.  The case of human to human transmission which we're certain about is in a family member, following what we think is quite close contact, and in fact, the recipient that the person that seems to have caught the virus from a family member is themselves somewhat susceptible to viruses.  We don't know the medical details but we have understood that they have some predisposition to make them particularly susceptible.  So, this human to human transmission event that's been seen with the new coronavirus does not necessary mean that this virus has the ability to transmit readily from people through the air, in a manner which we would begin to think was heralding a new pandemic.

Ben -   And obviously, we do have to be careful not to alarm people.  How can the medical community now be vigilant or what are we looking out for before we know that we may need to take action?

Wendy -   Well, the signs of this virus are pretty severe.  We're talking about severe respiratory illness.  Some of the patients have experienced kidney failure as well, but it's not clear whether that's direct consequence of virus infection or whether it's associated with the multi-organ failure that goes with such a severe respiratory infection.  The Health Protection Agency is looking at this very seriously.  They're very much involved.  They have diagnostic tests available and I'm quite sure that clinicians involved in sort of caring in ITU's to these kinds of patients will be strongly encouraged to submit those diagnostic tests and confirm cases as soon as possible.