The coronavirus has mutated into at least two separate strains since the outbreak began in December, according to Chinese scientists.
Researchers say there are now two types of the same coronavirus infecting people – and most people seem to have caught the most aggressive form of it.
At least 94,000 people have been infected around the world and almost 3,200 have died, while just over 50,000 have recovered from the disease.
The team of experts from Beijing and Shanghai said 70 per cent of people have caught the most aggressive strain of the virus but that this causes such bad illness that it has struggled to spread since early January and appears to remain in China.
Now an older, milder strain seems to be becoming more common.
In their study of genes in 103 samples of the coronavirus, which is named SARS-CoV-2 and causes a disease called COVID-19, they revealed they had discovered two distinct versions of it, which they named L and S.
They claimed that around 70 per cent of patients have caught the L strain, which is more aggressive and faster-spreading than S.
But L has become less common as the outbreak has gone on, with it apparently struggling to spread since early January, while S has become more common.
The scientists’ explanation suggests that, because the L strain surged at the beginning of the outbreak and made people so ill, those who caught it were quickly diagnosed and isolated, meaning it had less opportunity to spread widely.