There are now more than 400 known cases of the new virus that has spread to several Chinese provinces, as well as countries including the US, South Korea and Thailand. And Chinese authorities are warning that the coronavirus - which has killed nine people and has been confirmed as transmittable from person to person - could mutate and spread further.

The warning comes as millions of people are travelling across China for the Lunar New Year festival, which is expected to lead to more cases. Here is what we know so far about the virus.

And we ask how worried should people be?

The opening skirmishes in US President Donald Trump's impeachment trial have been taking place in the Senate, with the Republican majority rejecting Democratic attempts to secure new evidence. But majority leader Mitch McConnell backed off plans to fast-track the hearings, after Democrats said this would amount to a cover-up.

Mr Trump - who is charged with abuse of power and obstructing a congressional inquiry - described the trial as a "hoax" when he spoke at the World Economic Forum in Davos, Switzerland. He is unlikely to be convicted, as that would require the backing of 67 out of 100 senators. But there could be many hours of discussion ahead over the next six weeks. So what's going on? Find out here.

Also, we explain the Trump impeachment story in 100 words, 300 words and 800 words.

A crater some 2.2 billion years old - that's about half the age of the Earth - has been identified in Western Australia. Scientists say the asteroid that hit Yarrabubba could have accounted for a major warming event. Read all about it.

The Duchess of Cambridge is hoping to start a "national conversation" about early childhood, as she launches a survey, asking adults "Five Big Questions". The aim is to improve health and wellbeing.

"Trump versus Greta" is Metro's headline, as it and other newspapers react to the US president's speech on climate change at Davos, and campaigner Greta Thunberg's reaction. The Times describes the pair as exchanging "thinly veiled insults", while the i calls Mr Trump "Earth's number one climate change denier". Elsewhere, the Daily Mirror, the Sun and the Daily Star lead on Black Sabbath singer Ozzy Osbourne's announcement of his Parkinson's disease diagnosis. Read the newspaper review in full.

From elsewhere