Scientists with the MRC Centre for Global Infectious Disease Analysis at Imperial College in London warned in a paper published Friday that the number of cases in the city was likely to be closer to 1,700, much higher than the number officially identified.
Authorities said Sunday that some of the cases had “no history of contact” with the seafood market believed to be the centre of the outbreak.
No human-to-human transmission has been confirmed so far, but Wuhan’s health commission has previously said the possibility “cannot be excluded”.
Three cases have also been reported overseas — two in Thailand and one in Japan.
Although there has been no official announcement of screening measures on the mainland, Wuhan deputy mayor Chen Xiexin said on state broadcaster CCTV that infrared thermometers had been installed at airports, railway stations and coach stations across the city.
Chen said passengers with fevers were being registered, given masks and taken to medical institutions, with nearly 300,000 body temperature tests had been carried out, according to CCTV.
Authorities in Hong Kong have stepped up detection measures, including rigorous temperature checkpoints for inbound travellers from the Chinese mainland.
The US said from Friday it would begin screening direct flights arriving from Wuhan at San Francisco airport and New York’s JFK, as well as Los Angeles, where many flights connect.
Thailand said it was already screening passengers arriving in Bangkok, Chiang Mai and Phuket and would soon introduce similar controls in the beach resort of Krabi.
Wuhan is a city of 11 million inhabitants that serves as a major transport hub, including during the annual Lunar New Year holiday, when hundreds of millions of Chinese people travel across the country to visit family.