In late December, the Chinese authorities sent out a public notice warning that “pneumonia of unknown cause” had been identified in Wuhan, central China.
About 10 days later, on January 7, scientists announced that a new coronavirus was the source of the epidemic, quickly adding that it was not spreading among humans.
At that point, less than 60 cases had been found. But now the disease, named Covid-19, has spread to over 30 countries, infecting over 83,000 people and killing over 2,800.
This map shows where the disease is located, how many cases there have been and how many people have died:
How did the disease spread around the world?
Chinese health authorities have been praised for their rapid reaction to the disease and for their transparency in sharing genetic data. The quarantine of Wuhan and other Chinese cities is thought to have delayed the spread of coronavirus to other countries by a few weeks.
However, at the beginning of the epidemic, experts claimed that the disease did not spread easily from man to man, which has since been proven wrong, but may have contributed to the initial complacency.
And since many people who become infected suffer neither from symptoms nor from mild symptoms, the coronavirus was also able to spread under the radar. Some disease modelers believe that only 10% of cases in China and a third of the rest of the world have been collected.
This map shows how the disease has spread around the world in a relatively short span of time:
How quickly did the disease spread?
At the beginning of the epidemic, the number of cases increased slowly, but then it started snowing with thousands of new cases reported every day.
In mid-February the case definition changed to include clinically diagnosed cases, leading to a peak of over 14,000 new cases overnight. In late February, the number of new cases began to decline in China, but increased elsewhere.
This map shows how the number of cases has grown: