The WHO said it took more than three months to reach the first 100,000 confirmed cases worldwide, but only 12 days to reach the next 100,000.
While these figures are for confirmed cases, the actual number of people with coronavirus internationally is thought to be much higher – as many of those with mild symptoms have not been tested and counted.
In response to the virus’s spread, countries around the world are ramping up measures to try to slow it down.
Governments have halted flights from virus-hit nations, locked down towns and cities and urged people to stay at home.
President Donald Trump has declared a national emergency in the US and announced a travel ban on European countries, including the UK and Ireland, as well as China and Iran.
The US has now overtaken Spain with more than 30,000 confirmed cases.
Travellers from outside the EU are also being turned away from airports and borders after the 27-country bloc imposed a 30-day ban on entry.
Many international conferences and sporting events have also been cancelled or postponed, including Six Nations rugby matches, Euro 2020, the Copa America and this year’s meeting of G7 leaders in the US.