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BEIJING • China yesterday for the first time publicised a breakdown of people testing positive for the new coronavirus without outward signs of being sick, revealing that most of them remain symptom-free throughout infection.
Of 6,764 people who tested positive for infection without showing symptoms, only one-fifth - 1,297 - have developed symptoms and been re-classified as confirmed cases, China's National Health Commission spokesman Mi Feng said at a Beijing briefing yesterday. Some 1,023 are still being monitored in medical quarantine to see if they develop symptoms.
The phenomenon of asymptomatic transmission is a puzzling feature that has allowed the pandemic to spread wider and faster than previous outbreaks. While researchers earlier thought most patients end up showing symptoms, data indicating a sizeable group remains symptom-free throughout infection underscores the challenge of containing the widening pandemic.
Researchers are still struggling to understand asymptomatic cases: There's a possibility patients who seem to be symptom-free are actually manifesting symptoms that doctors do not know yet to look for.
For months, a fever and dry cough were understood to be the main markers, and it has only recently emerged that a loss of smell and taste is also a sign of infection. China has not disclosed the range of symptoms it looks for. It continued to detect asymptomatic infections even after new confirmed cases fell to zero for the first time last month. The virus has officially sickened some 82,000 and killed over 3,000 in China.
The number of asymptomatic infections is likely higher than the 6,764 China has detected. These cases were found through efforts to test the contacts of confirmed patients. Otherwise, those who show no signs of being sick have no reason to seek out testing on their own.
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