The outbreak was declared a global pandemic by the World Health Organization (WHO) on 11 March. This is when an infectious disease is passing easily from person to person in many parts of the world at the same time.
The WHO said it took more than three months to reach the first 100,000 confirmed cases worldwide, but it took less than a week for the number to double from 500,000 to a million.
The true figure for the number of people with coronavirus is thought to be much higher as many of those with milder symptoms have not been tested and counted.
China says it has now all but stopped the spread of the disease and the authorities have started to allow some access to Wuhan, the city in Hubei province where the outbreak began.
South Korea, where a major outbreak began in February, has also seen its number of cases fall in the last couple of weeks.
But badly-affected countries like Italy, Spain and the US are still ramping up measures to try to slow down the spread of the virus.
Governments across the world have halted flights, locked down towns and cities and urged people to stay at home.