Why is this outbreak more difficult to stop than Sars?
The answer is not down to China – the speed and scale of the country’s response to this new virus is widely considered to be unprecedented. The difference is the way the virus behaves inside the human body.
Sars was a brutal infection that you couldn’t miss – patients were contagious only when they had symptoms. This made it relatively easy to isolate the sick and quarantine anyone who might have been exposed.
But the new virus, 2019-nCov, is harder to spot and therefore harder to stop.
From the virus’s perspective, it has a far smarter evolutionary survival strategy than Sars.
The best estimate is only one-in-five cases cause severe symptoms, so instead of infected people turning up in hospital, you have to go out and find them.
And we are getting detailed documented cases of people spreading the virus before they even have symptoms.
There is a tendency to focus only on how deadly a virus is. But it is this, in combination with a virus’s ability to spread, that determines its true threat.