Although the total number of confirmed cases worldwide – 85,403 – is tiny, it is the
rate of growth which makes it alarming. The doubling time appears to be somewhere between 3 and 5 days. The same pattern also seems to occur in individual countries. To begin with, just one or two case are confirmed; and these are all people who have recently returned from a known affected area. Initially, the disease control agencies seem to have the condition under control. But a few new cases – also people that have returned from affected regions – continue to pop up. And then the condition spreads to people who have not travelled themselves, but have had contact with someone who has. A tipping point is reached when the first case is confirmed of a person who has neither travelled nor been in contact with anyone who has travelled. This occurred
here in the UK on the weekend. If the UK follows the pattern seen in Italy and across Asia, we can expect the numbers to grow rapidly from this point (as I am writing, the
BBC is reporting a further 12 confirmed cases).