Wuhan health authorities said Sunday morning that 17 more pneumonia-like infections have been confirmed in the central Chinese city, far more than the four new infections disclosed in a previous official update.

Before Thursday, the number of reported novel coronavirus cases in the city had remained at 41 for nearly two weeks, ever since health authorities acknowledged the mysterious illness for the first time on Dec. 31. As of Friday, however, that number had risen to 62 — with 19 patients fully recovered, eight in critical condition, two dead, and the rest hospitalized but in stable condition.

In an interview with Hong Kong-based newspaper Takungpao, Guan Yi, a professor of infectious diseases at the University of Hong Kong, said the maximum incubation period for a coronavirus is 15 days. “No new cases have been reported since Jan. 3, which shows that the outbreak has been brought under control,” Guan was quoted as saying on Wednesday. In the following two days, 21 new cases were reported.

In a daily news release Saturday, the Wuhan Health Commission said that close contacts of three confirmed novel coronavirus patients — two in Thailand and one in Japan — are under medical observation. “Only one close contact of the first confirmed patient in Thailand revealed symptoms of mild fever and coughing. No other abnormalities have been observed so far,” the statement said.

On Friday, scholars in the U.K. published a report estimating that there may have been over 1,700 people showing symptoms of coronavirus infection in Wuhan alone as of Jan 12. The researchers at the MRC Centre for Global Infectious Disease Analysis at Imperial College London explained that their estimate was based on several assumptions including 3,301 air passengers traveling internationally from Wuhan each day, as well as a 10-day delay between infection and detection.

However, some Chinese experts have questioned the methodology behind such a high estimate. “They (the ICL researchers) used a model for common infectious diseases to reach their conclusion, but the transmission method of the novel coronavirus in Wuhan remains unclear,” Wang Yuedan, a professor of immunology at the Peking University Health Science Center, told Sixth Tone on Sunday.

Last week, Wuhan’s health authorities acknowledged that the possibility of limited human-to-human transmission could not be ruled out for the new coronavirus, though the risk of such transmission being sustained over time should be low.

The South China Morning Post reported Saturday that three suspected cases have been detected in Shenzhen and Shanghai, citing sources familiar with the matter. Health authorities in Shenzhen declined to comment for the report and had not issued an official statement by time of publication.

On Sunday evening, Shanghai’s health authority responded to public concerns, saying the city is taking preventive measures against the virus. “All medical facilities have allocated more staff to their fever departments. Standardized monitoring, screening, diagnosis, and treatment will be carried out for suspected cases,” the statement said.

As to why there have not been confirmed reports of coronavirus infections in other mainland cities besides Wuhan, Professor Wang says this is likely because tests for the virus aren’t yet widely available.

With less than a week to go before the Spring Festival holiday officially begins, China has already entered the year’s peak travel period, chunyun, sometimes described as the world’s largest human migration. This year, state authorities estimate that 3 billion trips will be made over the 40-day period beginning Jan. 10.

Wuhan authorities said Sunday that they have enforced new measures aimed at preventing the virus from spreading, including installing infrared thermometers at the city’s international airport, train stations, and long-distance bus terminals; cancelling nonessential large public events over the Spring Festival period; and strictly managing fever departments at local medical institutions.

The World Health Organization has advised people in affected areas to avoid close contact with anyone showing symptoms of acute respiratory infection; to wash hands frequently, especially after direct contact with sick people or their surroundings; and to stay away from live or dead animals other than household pets.

Professor Wang suggests that more publicity work should be carried out to alert people about the new virus.

“The public should be able to get some basic understanding of the virus and the prevention methods,” he said. “Better ventilation and sterilization work should be carried out in public places like train stations, and inspection and quarantine work should be carried out in key high-risk areas.”

Editor: David Paulk.

(Header image: Li Gang, the head of Wuhan’s center for disease control and prevention, delivers an update about the city’s novel coronavirus outbreak during a press conference in Wuhan, Hubei province, Jan. 19, 2020. Xiao Yijiu/Xinhua)