The coronavirus might spread much faster than health officials initially believed, according to a new study.
The virus's "doubling" rate - passing from one person to another leaving two people infected - was initially given at between six and seven days, reported the New York Post.
But the American research team put this figure at 2.3 to 3.3 days early on in the Wuhan epidemic, suggesting a much faster rate of spread than initially measured.
Each person infected early in the epidemic in Wuhan probably passed the virus to an average of 5.7 other people, according to a mathematical analysis from Los Alamos National Laboratory.
The study found that 82 percent of people would have to be immune - either via a vaccine or from recovering from the disease already - to stop it spreading.
Figures released at the start of the outbreak claimed one person would infect 2.2 to 2.7 people.
When the outbreak first began, researchers thought the virus was spreading at a rate of between 0.1 and 0.14, half the 0.21 and 0.30 figure established now.
Scientists found that the incubation period - the time from when a person is first exposed to the bug to when they start showing symptoms - is 4.2 days, one day shorter than two previous estimates.
The virus was first detected in Wuhan, China, in December 2019 before spreading worldwide, killing 109,000 and infecting more than 1.7 million so far.
Before January 18, the time from when symptoms first showed to hospitalisation was 5.5 days in China. After January 18, the duration shortened significantly to 1.5 days.
Scientists said this came at the same time as reports of potential human-to-human transmission and the country's emergency response level upgrading.
China sealed off the city of Wuhan on January 23, when it became apparent the deadly Covid-19 virus had started there.