LONDON – The World Health Organization held off declaring the novel coronavirus infection that has emerged in Wuhan, China, an international public health emergency, despite the fact that the number of confirmed cases tripled in the past week and the infection has spread to several other countries, including the U.S.

The decision follows the convening of WHO’s Emergency Committee in Geneva on Jan. 22 to consider if the outbreak of the coronavirus, labeled 2019-nCoV, is of international concern and requires an international response.

As the Emergency Committee deliberated, the authorities in China announced that Wuhan is to be put in quarantine, with all flights and trains out of the city canceled from 10 a.m. local time Thursday Jan 23.

After deliberating all day Wednesday, the committee said it needed more time. “To proceed, we need more information,” said Tedros Adhanom Ghebreyesus, director general of WHO, speaking after the meeting, which closed two hours later than expected.

“The decision is one I take extremely seriously; one I am only prepared to make with adequate consideration of all the information,” Ghebreyesus said.

As of Jan 22, there have been 460 confirmed cases and nine deaths. Away from the epicenter in Wuhan, a city with a population of 11 million, infections of 2019-nCoV have occurred in 13 provinces and four cities in China.

To date, a total of eight cases have been diagnosed outside China, in the U.S., Japan, Thailand, South Korea, Macau and Taiwan.

It was confirmed for the first time this week that human-to-human transmission is occurring.

Speaking in London earlier on Wednesday, Neil Ferguson, director of the Medical Research Council Center for Global Infections Disease Analysis at Imperial College London, said declaring an international emergency is a finely balanced decision. “There are arguments both ways, but the rapid increase in the number of cases and the export of infections, means that formally the threshold has been reached,” he said.

Declaration of an international public health emergency extends reporting and information sharing requirements to all WHO member states. However, Ferguson said, “We see that happening anyway.”

The outbreak of 2019-nCoV has raised the specter of an earlier novel coronavirus, which caused SARS (severe acute respiratory syndrome) that emerged in China late in 2002. In that case, the Chinese authorities did not share information and the virus spread to 37 countries, causing 8,000 infections and 750 deaths.

On this occasion, “information is coming in regularly from China, unlike SARS,” said David Heymann, professor of Infectious Disease Epidemiology at the London School of Hygiene and Tropical Medicine, who as head of WHO’s Communicable Disease Cluster, headed the global response to SARS.

The flow of information from China on 2019-nCoV has enabled WHO to respond promptly, setting up three virtual expert committees, covering clinical impact, epidemiology and virology of the new virus, Heymann said.

Josie Golding, epidemics lead at the U.K. medical research charity Wellcome Trust, agreed there has been good risk communication by the Chinese authorities. The response also was expedited by significant technical advances since SARS, she noted.

“China now has surveillance systems in place to be able to detect that this was something different. They were able to detect an increase in the number of cases of severe pneumonia and were able to develop a diagnostic test, and through [DNA] sequence analysis to show this is a novel virus,” Golding said.

However, significant gaps in knowledge about 2019-nCoV remain, including around the range and severity of symptoms, the incubation period, the length of time people with the virus remain infectious, the exact mode of transmission, where the virus originated, and how to treat it.

State of knowledge

Ferguson said the rapid increase in the number of cases over the last week is likely a feature of this being early days in dealing with the outbreak. “It is difficult to develop a diagnostic and work out how to do surveillance. Hospitals [in Wuhan] are overwhelmed with suspect cases. It’s an enormous and demanding situation,” he said.

“I expect the case numbers will continue to increase rapidly [but] one has to be careful in interpreting increases: it is likely to be [a case of] the health authorities catching up,” said Ferguson.

Knowledge of the virus is based on patients who are ill enough to be in the hospital, noted Peter Horby, professor of Emerging Infectious Diseases at Oxford University. “Clinicians in China are working day and night, and they are reporting what they know about the hospitalized cases. I think it is very important to understand they are a subset of all infections, so it is very difficult to confirm the severity of the disease,” Horby said.

The state of knowledge is that there is a long latency period, with patients developing a dry cough a week after infection. In severe cases, that progresses to breathlessness and may result in a need for patients to be ventilated.

Based on existing data, there is a 2% fatality rate, which is comparable to the Spanish flu epidemic of 1918.

But Horby said, “It seems there is quite a protracted course, so we can’t at the moment conclude what the fatality rate is.”

It also is unknown when patients are at their most infectious, and as a novel virus, 2019-nCoV is likely to spread faster than one like flu which circulates all the time, because there is no immunity.

Ferguson said the severity of the symptoms caused by SARS meant it was easy to identify cases, making it easy to control. “One of the challenges being faced here may be that it is a milder disease, but people showing mild or no symptoms are still infectious,” he said.

As a result, controls that have been put in place for people traveling within China, or arriving in other countries on flights from China, “have a degree of effectiveness, but are not a panacea,” according Ferguson.

“If a person was infected two days before travel, they will arrive without any symptoms,” he said. “I can understand that countries want to try and reduce the threat by measures at their borders, but borders are porous. China has had exit screening since [Jan] 17 and the virus has still been exported.”

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