The world should be more anxious than it was a week ago. According to research published on Friday, a new Sars-like coronavirus has been present in China since December 1, a full month before the alarm was raised. Almost 3,000 people have been diagnosed with the respiratory illness. As of Monday afternoon, 35 cases were outside China. Eighty-one people have died. Despite draconian quarantining, the virus, provisionally known as 2019-nCoV, is spreading. Several countries, including the UK, are considering evacuating nationals from the hot zone. It is now time for the World Health Organisation to call a Public Health Emergency of International Concern (PHEIC).

The revised timeline on when the virus began circulating comes courtesy of two papers in The Lancet medical journal, which reveal other worrying details. One sets out the clinical data on the first 41laboratory-confirmed patients. Patient zero, who fell ill on December 1, had no link to the seafood market in Wuhan that is widely assumed to be the source of the outbreak. A further 13 of those 41cases showed no link either. It is possible that the virus began circulating earlier than December. Other analyses separately suggest that containment is now a forlorn hope. The “reproduction number” is thought to lie between two and four – meaning that, on average, each infected person passes the virus to between two and four others. That is high: seasonal flu has a reproduction rate of about 1.4.

The incubation period could be about a week, with infected individuals possibly being contagious while showing mild or no symptoms. Neil Ferguson, an Imperial College epidemiologist, estimated that 4,000 were infected by January 18. Jonathan Read, of Lancaster University, and colleagues provisionally calculate that the tally could exceed 190,000 by February 4. A “gravesituation” for China, as President Xi Jinping describes the epidemic, is a grave situation for the world. Afifth of the global population is now potentially exposed to a highly transmissible, currently incurable and potentially fatal respiratory virus.

Richard Horton, editor-in-chief of The Lancet, believes a PHEIC declaration should be considered. “The emergency committee [of the WHO] should reconvene as a matter of urgency,” Mr Horton said, adding that hefelt there were political sensitivities at play that have not dogged other epidemics, such as Ebola in west Africa.