To curb the spread of the virus, authorities closed off Wuhan, the provincial capital of Hubei, by stopping outbound planes, trains and buses on January 23. All public transport and private vehicles were also banned in the city, which is home to more than 11 million people.

Chinese officials expanded transport restrictions to at least 15 surrounding cities with a combined population of over 50 million people.

Raina MacIntyre, professor of global biosecurity at the University of New South Wales in Sydney, said that in theory “any intervention that reduces travel should be effective from spreading the infection outside the affected area”.

“But many people from Wuhan had already left for [Lunar] New Year before lockdown, which may explain the cases in other parts of China. We have to see if the epidemic growth slows in Hubei and outside Hubei in the next few weeks,” MacIntyre said.

“The incubation period is up to two weeks, so we may therefore expect to see more impact of the lockdown in the next few weeks.”

Joseph Tsang Kay-yan, a Hong Kong infectious disease specialist, said the lockdown would help efforts to contain the outbreak but the numbers would continue to rise for the next month or so.

“[University of Hong Kong] experts have predicted that the peak of the rise in case numbers will occur around late April. I think that the case numbers will continue to climb up in the next four to eight weeks’ time,” Tsang said.

“I do think the lockdown is an important measure from a global perspective, because it helps [minimise] the spread of cases worldwide.”

But Lawrence Gostin, professor of public health law at Georgetown University in Washington, said mass quarantines like the one in Hubei province were “at best ineffective and at worst counterproductive”.

“By confining people in a congested hotzone of active contagion, there will be cross contamination among family, friends, and neighbours. And China is losing the trust and cooperation of the population,” Gostin said.

“I believe China should adopt rigorous testing, treatment, isolation and contact tracing, including enhanced screening for inhabitants leaving Hubei.”

The virus, which first emerged at the end of December, has killed almost 500 people and sickened more than 24,000, including in Thailand, Australia, Germany and the United States.

Infections have been confirmed across all of China’s 31 provinces, municipalities and autonomous regions.

“The number of cases are mounting rapidly. It is hard to predict when they will level off given the sheer size of the population. But I do hope that we will reach a plateau in the coming weeks,” Gostin said.

“If active public health measures were adopted I would hope to see a levelling off of cases in the next few weeks. But we need to be prepared for the possibility that China will not fully contain the virus and it will become endemic and/or seasonal. We should make every effort to avoid that scenario.”

John Edmunds, professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine, said that data from China was so crude that it was impossible to get an accurate picture of what was going on.

“Also, given that the serial interval appears to be reasonably long, then it would take a bit of time for effects to be seen,” Edmunds said, referring to the time between cases in a chain.

Yanzhong Huang, senior fellow for global health at US think tank the Council on Foreign Relations, agreed that it was still too early to say if the “draconian containment measures” had been effective if effectiveness was measured in terms of the number of newly infected cases.

“So far we haven’t seen the light at the end of the tunnel,” Huang said.

“Instead, it is very likely China is entering the darkest before dawn ... It appears that the plateau of transmission has not arrived in other parts of China.”