9 Jul 2013

Why Mers CoV is top of most virologists’ watch list

If it was up to me, I’d say the worryingly deadly Middle East respiratory syndrome coronavirus (Mers CoV) won’t lead to a global pandemic. But nine months after the virus was first discovered, there is still so much uncertainty about this mysterious disease, I’m very glad I’m not the one that has to make that call.

That job falls to a network of expert virologists and public health officials, many of whom met in London today to decide just how woried we shoud be about about Mers CoV. And righ now they don’t really know what to conclude.

First, take a look at what they know: as of today there have been 81 confirmed cases of the virus and 45 deaths. A virus that kills that many people (a case fatality rate of more than 50 per cent) should cause alarm among our public health officials.

The vast majority of cases and deaths (39) have been in Saudi Arabia linked to an as-yet unidentified source. But cases and deaths have also occurred in other countries – most of them in the UK, which has now seen four cases and three deaths. All had links to the Middle East.

The virus is also in the same family as the Sars virus which in 2002/3 caused a global epidemic of more than 8,000 cases and killed 775.

“Because of the memory of Sars, there is a lot of international concern,” Brian McCloskey, director of global health for Public Health England, told Channel 4 News. “And based on the first confirmed case of the virus, we know it can travel.”

That case, a 49-year-old Qatari man who travelled to the UK and fell gravely ill in September last year, died only 10 days ago in a London hospital after a long and gruelling battle with the virus.

But there are other things about Mers CoV that emerged at today’s meeting that suggest we shouldn’t panic just yet.

First, it looks to be spreading slowly. The Sars virus that caused the outbreak in 2003 went round the world in weeks. It also infected large numbers of young healthy people (including nurses and doctors in masks) who came into contact with it.

Mers CoV seems to prefer older people, with pre-existing medical conditions. New research from Saudi Arabia is also suggesting it may be present in larger numbers of people where it causes little or no illness. That would mean the 50 per cent plus mortality rate is in fact wrong – based purely on the most serious cases that actually end up in hospital.

And in some ways Mers CoV is just weird. It seems to have a preference for men. 65 per cent of cases have been in middle-aged men. However, experts from Saudi Arabia cautioned this could be due to cultural factors – like women covering noses and mouths in the kingdom – rather than biological ones.

The virus also seems to be much more transmissible in some situations than others. Based on testing of family contacts, it appears quite hard to catch outisde hospitals. But in other cases – in the UK and Italy – family members picked up an infection after just a few minutes visiting a sick loved-one in hospital.

At today’s meeting scientists concluded more effort has to be made to produce a rapid and effective test for the virus. Only that will reveal how widespread, and therefore how deadly, the virus actually is.

They also decided more work needs to be done to find whether there is an animal host for the virus. Mers CoV is most closely related to similar viruses in bats. But Channel 4 News understands researchers in the Netherlands are close to identifying an intermediary animal host – perhaps livestock – that is harbouring Mers CoV.

In the next 48 hours the World Health Organisation emergency committee is meeting to decide whether Mers CoV consititutes a “public health emergency of international concern”. It has a rival in the form of an equally nasty-looking new flu strain circulating in China called H7N9. But whatever they conclude this virus is likely to remain at the top of most virologists’ watch list for a while to come.

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