China’s Asymptomatic Coronavirus Case Numbers Don’t Tell the Whole Story
China’s health authorities began regular updates Wednesday of national tallies for asymptomatic Covid-19 carriers amid pressure from the public and senior officials to disclose the information. Yet the numbers so far do not reveal the true scale of this category of individuals infected by the coronavirus.
As of Tuesday night, the Chinese mainland had 1,367 asymptomatic individuals who were under medical observation, according to data (link in Chinese) released Wednesday by the National Health Commission (NHC), China’s top health body. The number represented a net decrease of 174 individuals from the previous day, the announcement said. With the country counting 2,004 active symptomatic cases Tuesday, those without signs of illness accounted for 41% of active infections.
According to the data, which was part of China’s very first regular report that included information on asymptomatic individuals, the NHC on Tuesday added 130 such infections to its tally and removed 302 who had completed their quarantines. Furthermore, two individuals have been reclassified from asymptomatic to “confirmed” cases, a category that in China only includes individuals who have both tested positive and show signs of illness, as per China’s national Covid-19 prevention and control protocols.
As the data does not reveal the numbers of asymptomatic individuals that have previously completed quarantine and are no longer under medical observation, the tally is a snapshot of active cases, rather than a cumulative total.
According to national protocols, despite having tested positive for Covid-19 in the lab, asymptomatic individuals are not counted in China’s publicly disclosed “confirmed” cases, in contrast with many other countries around the world. Previous versions of the NHC’s daily coronavirus updates only included “confirmed” and suspected cases, though in recent weeks, as China’s domestic outbreaks appeared to ebb, statistics on imported cases of Covid-19, or infections among foreign arrivals, were added to the NHC’s reports.
The updates to epidemic reports follow at least two calls by Chinese Premier Li Keqiang to focus on containing asymptomatic carriers, which numerous studies have shown to be contagious, as well as public calls for transparency about the size of this population. The NHC announced Tuesday that it would include the latest information on this group in its reports starting Wednesday in an effort to address public concerns.
In light of this announcement, some, though not all, provinces have also unveiled local tallies, though using various accounting methods and at varying levels of detail.
Among them, Liaoning was one of the only provinces to reveal a grand total. In its Wednesday report, the provincial government said that it had 52 accumulated asymptomatic infected individuals by the end of Tuesday, of which 12 had completed quarantine, 23 had been reclassified to “confirmed,” while 17 were “being treated in hospital.” It also revealed tallies for the close contacts of this population, which the province was monitoring. Its total "confirmed" cases numbered 140 the same day.
In contrast, Shanghai claimed that it had no asymptomatic infected individuals after one person was cleared of the virus and 10 developed symptoms in hospital.
Hubei province, the epicenter of China’s epidemic, said it had 982 asymptomatic carriers Tuesday, including 47 such infections it detected that day. The province also disclosed that one other case was reclassified as “confirmed,” while 289 had completed quarantine.
Caixin previously reported that, despite China reporting few to no “confirmed” cases across the country, Hubei’s capital, Wuhan, alone detected up to a dozen or more asymptomatic infections a day using methods that included contact tracing and screening of high-risk individuals, such as quarantine workers.
Despite not publicly disclosing statistics on asymptomatic individuals, the NHC has demanded the prompt detection and reporting of those with light or no symptoms since late January and has treated them as a potential source of contagion. Most recently, detected asymptomatic individuals were subject to a 14-day quarantine and were required to test negative in two separate nucleic acid tests before being released.
A study published Feb. 12 in the Chinese Journal of Epidemiology suggested that asymptomatic infected individuals accounted for only 1.95% of all lab-confirmed infections. According to data Caixin obtained, asymptomatic individuals accounted for more than one in six detected infections in the province of Heilongjiang on Feb. 25.
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