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China coronavirus: mild but infectious cases may make it hard to control outbreak, report warns

BMJ 2020; 368 doi: (Published 28 January 2020) Cite this as: BMJ 2020;368:m325

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  1. Elisabeth Mahase
  1. The BMJ

Uncertainty over the severity spectrum of the novel coronavirus (2019-nCoV) and whether people with mild symptoms can efficiently transmit the virus mean it is currently “unclear” whether the outbreak can be contained within China, a report from Imperial College London has warned.1

The update from the MRC Centre for Global Infectious Disease Analysis said that the rate of transmission could come down as people become aware of the threat and try to avoid becoming infected, as happened with severe acute respiratory syndrome (SARS).

But it raised concerns over reports of mildly symptomatic but infectious cases, which were not a feature of SARS. Detecting and isolating these cases would be “extremely challenging,” considering the number of conditions that can cause non-specific respiratory symptoms, it said.

The researchers said that controlling the situation would require “successful detection, testing, and isolation of suspect cases with the broadest possible range of symptom severity,” and they called for efforts in these areas to be as “extensive” as the capacity of health services allow.

As at 28 January 4520 confirmed cases and 106 deaths had been reported in China (including Macau). Most cases (2714) are in Hubei province, where the outbreak began. Outside China 15 countries have reported cases. These are Thailand (14 cases), Hong Kong (eight), the US (five), Taiwan (five), Australia (five), Singapore (four), Japan (four), South Korea (four), Malaysia (four), France (three), Canada (two), Vietnam (two), Nepal (one), Cambodia (one) and Germany (one).2 No deaths have been reported outside China.

The initial source of 2019-nCoV is still unknown, but the first cases were linked to a seafood market (which was closed on 1 January) in the city of Wuhan, capital of the central Hubei province.3

The transmissibility of 2019-nCoV report, published on 25 January, said that based on the estimated R0 (reproduction number) of 2.6 (uncertainty range: 1.5-3.5), “control measures need to block well over 60% of transmission to be effective in controlling the outbreak.”

Despite the WHO Emergency Committee deciding not to declare a Public Health Emergency of International Concern at this time, this epidemic represents a “clear and ongoing global health threat” and it is “critical that the magnitude of the threat is better understood,” the report concluded.

Chinese authorities have so far quarantined 17 cities, affecting 50 million people, as part of efforts to contain the outbreak. They have also added three days to the Chinese New Year holiday in the hope that this will slow the pace of transmission by keeping people at home. Meanwhile, Mongolia has closed its border with China, and Hong Kong and Malaysia have said they will block entry to visitors from the Hubei province where the outbreak started.4

Writing in The BMJ, researchers from King’s College London have warned that “regardless of whether it succeeds in controlling the outbreak, the widespread lockdown will inevitably have a psychological effect.” However, they added that care must be taken to ensure fears are not overblown.5

“Journalists regularly assume panic based on little if any evidence and in our experience, the further away a reporter is from an incident, the more likely they are to claim panic,” they wrote.

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