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Three-fifths of new cases of coronavirus in China showed no symptoms of the disease when diagnosed, according to data that is likely to complicate movements by governments around the world to lift strict blockade measures.
A Financial Times analysis of the most comprehensive data on Covid-19 that the Chinese government began publishing in early April found that 60 percent of confirmed cases recorded in the past month were not symptomatic at the time of the test.
The prevalence of non-symptomatic cases will be a concern for authorities not only in China but around the world as they seek to reopen their countries after months of closings. It suggests that there are likely to be large numbers of people in the community spreading the virus without knowing it.
This is a particular concern since many public health experts believe that carriers are more infectious in the pre-symptomatic stage of the disease.
Lack of worldwide testing capacity means that it is extremely difficult to know how many virus carriers are not symptomatic. But the evidence there is suggests that it is a substantial proportion.
In the Italian city of Vò, which evaluated all of its 3,300 inhabitants, about half of those who initially tested positive had no symptoms. In Iceland, health authorities found that 43% of those infected showed no symptoms at the time of the test. Research by the South Korean Centers for Disease Control and Prevention on two groups of particles in the country found that the proportion of people without symptoms was 30% to 36%.
Beijing has been thrilled with its success in fighting the spread of the virus and in reducing the new case count that peaked at more than 5,000 a day in February. He claims to have effectively ended the local spread of the virus, and has been reporting fewer than 100 new symptomatic cases per day for the past two weeks.
Most of the new symptomatic cases are imported by people who bring it into the country from abroad and also do so in a minimum quarantine of two weeks, although the Chinese media have criticized some leaky quarantine procedures.
Local cases are of greater concern, as they present an increased risk of spreading a second wave of infection as blocking measures are lifted. While the center of the Wuhan outbreak has had no new symptomatic cases for nearly a month, around 20 new, non-symptomatic carriers have been detected every day through mass testing.
China’s data on non-symptomatic cases is a feature of its approach to testing and tracking contacts of confirmed cases, meaning that the system can catch victims who would not otherwise visit a hospital for testing. South Korea has also reported non-symptomatic cases through tests of infection groups.
Zhong Nanshan, the de facto medical spokesperson for the Chinese government, has tried to reassure citizens about non-symptomatic cases and reminds them to be vigilant. “I don’t think non-symptomatic cases are a big risk,” he told state media this month. However, just a few days before, the National Health Commission warned that these cases were “contagious and carry the risk of spreading the disease.”
China’s largest recent group of cases, in the north-eastern city of Harbin, includes non-symptomatic carriers in the transmission chain. According to the authorities, a returnee from the USA. USA It caused the infection of at least 71 people, including non-symptomatic spread.
“There is now very good evidence that the maximum elimination of [the virus] It is from the pre-symptomatic phase of the infection. There is also strong evidence from mathematical models that 40-80 percent of transmission comes from individuals to or pre-symptomatic, “said Babak Javid, a professor of medicine at Tsinghua University in Beijing.” As such, pre-infection -symptomatic poses a risk of contagion. “
Additional reports from Donato Paolo Mancini in London and Jung-a Song in Seoul
