Virologist Guan Yi told Chinese news outlet Caixin that he thinks the Wuhan coronarvirus could reach "10 times the scale" of the 2003 SARS outbreak.

Chinese authorities missed the "golden time" to halt the spread of the disease, since people had already begun their Lunar New Year travels, he said.

A Chinese professor predicted that the outbreak will peak in March and could last into early May.

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The Wuhan coronavirus, which scientists believe jumped from a snake to a human, has infected more than 600 people across nine countries and killed 18. The outbreak prompted five cities in China to halt all transportation. Cases have been reported in eight other countries.

But we haven't yet seen the worst of this new illness, a Chinese virologist says.

The coronavirus outbreak could reach 10 times the scale of the 2003 outbreak of severe acute respiratory syndrome (SARS), Guan Yi told Chinese news outlet Caixin. Guan helped identify the SARS virus, which was also in the coronavirus family. It affected more than 8,000 people and killed 774. The new coronavirus, however, appears to be far less deadly than SARS.

The reason Guan thinks this outbreak could be worse than SARS is that Chinese authorities missed the "golden time" to halt the spread of this coronavirus, he said. People started their Lunar New Year trips — the country's busiest travel period — before the city of Wuhan, where the outbreak started, was put on lockdown. Guan estimated the incubation period of the coronavirus to be about eight days.

"I don't think the local government has done what it should do. They haven't even been handing out quarantine guides to people who were leaving the city," Guan, who quarantined himself after visiting Wuhan, told Caixin.

A now-deleted post from Wuhan Railway said 300,000 people traveled by train out of Wuhan on January 15, the Washington Post reported.

Guan also said that when the Huanan Seafood Wholesale Market in Wuhan was washed clean — that's where experts think the outbreak originated — critical evidence got lost.

A boy hugs a relative as she leaves to board a train at Beijing Railway station on January 21, 2020. Health officials have stepped up efforts to contain the spread of the pneumonia-like coronavirus. Kevin Frayer/Getty Images

Eric Toner, a scientist at Johns Hopkins University, previously told Business Insider that although this coronavirus seems to be significantly milder than SARS, "it may be more transmissible than SARS, at least in the community setting."

The outbreak's peak could be months away

Meanwhile, a Chinese professor who teaches agricultural economics in Germany, issued a different — but equally dire — warning.

The virus outbreak is expected to peak 90 days after its start, Yu Xiaohua told the South China Morning Post. That would be in March. Its effects could be felt into early May, Yu wrote on the Chinese social-media platform Weibo.

His prediction was based on a mathematical model that used data from the SARS outbreak, Yu said. However, he told the 21st Century Business Herald, a Chinese newspaper, that the forecast doesn't take into account the government's ongoing attempts to limit the spread of the virus, including quarantining multiple cities.

Outside of China, cases of coronavirus have been reported in the US, Thailand, Japan, South Korea, Taiwan, Vietnam, Singapore, and Saudi Arabia, as well as the cities of Macau and Hong Kong.

Videos are emerging of patients being transported in metal boxes or plastic tubes to limit the spread of the virus. The US patient, meanwhile, is being treated in a hospital in Everett, Washington, where doctors are using a robot equipped with a camera, microphone, and stethoscope to minimize their own contact with the virus.

"I've never felt scared. This time I'm scared," Guan told Caixin.