Coronaviruses are a family of relatively large viruses. The name comes from the fact that, under a microscope, coronaviruses all look like they are surrounded by little halos. Those "coronas" are actually little proteins that cover the surface of the viruses and help them gain access to the cells they invade.
Although scientists think that coronaviruses are actually responsible for a significant percentage of the illnesses that we call the "common cold", the most famous coronavirus is SARS, which killed almost 1000 people in 2003. That doesn't sound like many, but comparing deaths to diagnosed cases reveals a fatality rate of 10%. (There's a good chance this number doesn't give you the full picture. It's likely more people contracted SARS than ended up diagnosed with it, simply because, if your illness isn't severe, you don't usually bother to get diagnosed. To provide some context, the 1918 flu pandemic had an estimated fatality rate of 2.5%.)
All of this explains why a newly identified coronavirus — which may be the cause of two deaths and a couple of outbreaks of respiratory illness in the Middle East — is getting so much attention and causing people to freak out a little. The virus (which doesn't actually have a name yet) is part of the same family as SARS. SARS was a scary virus. So this new virus has everyone a little on edge, too.
The key thing to remember, though, is that this new virus is not SARS. And there's a lot we don't yet know about it.
I want to point you toward a couple of sources you should be following as this story plays itself out.
First off, Vincent Racaniello's Virology Blog has some good background on the discovery of the new virus and will help you understand how scientists identify a virus, to begin with.
The novel coronavirus was first reported by Ali Mohamed Zaki on ProMED-mail on 15 September 2012, from a 60 year old male patient in Saudi Arabia with pneumonia and acute renal failure who died in July. The virus was isolated by culturing sputum on Vero and LLC-MK2 cells, and identified as a coronavirus by polymerase chain reaction. Dr. Zaki sent the virus to Ron Fouchier in the Netherlands who sequenced its genome and confirmed that it is a beta-coronavirus closely related to bat coronaviruses.
Ron Fouchier doesn't believe that we should become overly worried about these cases: "There are now six known human coronaviruses; one of them is SARS, but four cause the common cold and are quite innocuous. So let's keep both feet on the ground and not blow this out of proportion."
The fact that the virus has been isolated from individuals with severe respiratory disease does not mean that it is the causative agent. To prove this requires additional work, as Fouchier notes: "For starters, we'll find out whether animals get sick from this virus. You can isolate a virus from a patient, but that does not mean they died from it; to show that it causes disease you need to fulfill Koch's postulates. That's what we did for SARS, and it's what we hope to do here; we've applied for emergency ethical approval. The most obvious animal species to put this virus in are mice, ferrets, and perhaps monkeys." Proof that the new coronavirus is an agent of respiratory disease would come from its isolation from additional patients with the disease.
Next, head over to the Superbug blog, where journalist Maryn McKenna has some good information about the social context of this virus.
The concern underlying these developments is that exposure to the new virus seems to have occurred only or primarily in Saudi Arabia, which houses Mecca, the physical heart of Islam — and which, next month, will be the center of the worldwide annual pilgrimage known as the Hajj. The Hajj brings more than 2 million people to the country, in extraordinarily crowded conditions, and when those pilgrims leave, they disperse all over the world.
The spread of disease during the Hajj has always been a concern (discussed, for instance, in this UK document from 2005, when avian flu H5N1 was a cross-border threat), and the Saudi authorities have always taken it seriously, including requiring that pilgrims be vaccinated in order to be granted a visa. According to news reports today, they are ramping up scrutiny of visitors, who have already begun arriving: The first official day of the pilgrimage season this year is tomorrow, Sept. 27, though the central observances in Mecca do not begin until Oct. 24.
Finally, Helen Branswell is a health reporter for The Canadian Press. She covered the SARS outbreak in 2003 and is reporting on this new virus, as well. She's very good. Keep an eye out for her byline. That's news you can trust.
Professor John Watson, head of the respiratory diseases department at the Health Protection Agency, said to date there is no sign of spread to health-care workers.
That is important because health-care workers often serve as inadvertent sentinels of the spread of infectious diseases. During SARS, for instance, health-care workers were disproportionately affected, catching the new virus from patients they were struggling to save.
"Preliminary enquiries have revealed no evidence of illness in contacts of these two cases, including health-care workers," the British agency's release stated. "Based on what we know about other coronaviruses, many of these contacts will already have passed the period when they could have caught the virus from the infected person."