From the BBC:
Why Social Distancing is so important.
On Friday the UK experienced its biggest increase in deaths so far. Confirmed cases in the UK are doubling every three or four days. Deaths are growing faster, doubling every two or three days.
This isn't all cases, just the confirmed ones. That's because testing is mainly only carried out on those ill enough to be hospitalised, not those with mild symptoms, and so the true number of cases is higher.
Experts in the field would expect those wider cases to also follow a similar pattern: doubling every few days. That's because viruses multiply and so do the numbers of people infected by them. They keep multiplying at a constant rate until they run out of people to infect or measures to slow the spread take effect.
In reality, doubling speeds often fluctuate until an epidemic reaches a big enough number, say 100 cases. Since that point, confirmed cases in the UK have doubled every 3.3 days.
Thankfully, there haven't been enough deaths in the UK yet for us to draw a settled trend from 100, so our trend line starts from 10.
At the moment, deaths are growing faster than confirmed cases, doubling every 2.5 days. As of 27 March, the UK has seen 759 deaths. If the speed of doubling continued, we would expect to see another 750 deaths in the following three days and 1,500 in the 2.5 days after that. But is that speed faster or slower in the UK than in other countries?
But experts in viruses and epidemics have cautioned against assuming that countries will follow the same trajectory, even if there are similarities in early figures from each country.
There are some things that will be the same the world over like how long the virus takes to become infectious in someone's body. But how an outbreak develops after that depends on what measures countries take and when they act, and China brought in restrictions sooner than many other countries.
Scientists expect that each infected person will infect about 2.5 other people on average. As each of them infect another 2.5 and so on, a month multiplying at that pace leads to more than 400 new infections.
Halving that infection rate means that after a month, we'd expect to see just 15 new infections - a 95% reduction. That's because a small difference in the infection rate builds and builds to make a big difference in the number of people becoming infected. That's why social distancing is so important.
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