The real extent of the coronavirus-caused epidemic in Hubei province came under suspicion after Chinese authorities reported more than 13,300 other cases that have been diagnosed at an unspecified time in recent weeks.

The World Health Organization (WHO) said the recently reported cases in Hubei - bringing the number of infected worldwide to 60,000 - are the result of new counting criteria by Chinese authorities.

Cases where doctors have seen a chest infection on the graph are being classified as coronavirus. Previously, only patients who were analyzed were classified. As a result of this counting system, the death toll increased by 254, reaching 1370 worldwide since the virus began spreading. All the dead, except two, were in China.

In addition to the 13332 cases added on Thursday, Chinese authorities also reported 1820 other infected people whose diagnosis was confirmed by the analysis.

The WHO is working to find out more about the origin and duration of the epidemic in Wuhan and other cities in Hubei.

Adapted from The Guardian