Why more than 200,000 COVID-positive results in Shanghai aren’t ‘confirmed cases’

Shanghai resident Jean Yang has been skeptical about the city’s daily COVID-19 case numbers – more than 95 per cent of infections are not counted as confirmed cases.

The 30-year-old landscape designer, who lives on China’s equivalent of Wall Street in the country’s financial center, said official statistics were “too hard to understand”.

“How do they distinguish symptomatic and asymptomatic cases?” Ms Yang questioned from her apartment in Shanghai’s Pudong district.

“I can see those numbers every day on WeChat… But they don’t mean much to me.”

Between the start of March and Monday this week, 229,742 positive COVID-19 cases have been reported in the locked down city of Shanghai.

Local public health officials say that’s made up of 8,322 “confirmed cases” and 221,420 asymptomatic infections.

A worker in protective gear walks along shuttered shops in the Jingan district under lockdown in western Shanghai
More than 26 million residents in Shanghai are living in a city-wide lockdown.(AP: Chen Si)

The Chinese government insists those who are asymptomatic are not confirmed cases.

It means China’s total number of confirmed cases is a fraction of what it would be if it counted the same way most other countries do.

Dr Toole said the extremely high percentage of asymptomatic cases was also “not normal”.

“Saying that 95 per cent of all cases are asymptomatic is an exaggeration,” he said.

“I think by saying 95 per cent are asymptomatic and therefore only reporting 5 per cent, you distort the data.”

a girl is waiting in line with a white puppy in hear arms
Many Shanghai residents have expressed frustrations with the lockdown.(AP: Cheng Si)

Dr Joshua Szanyi, a public health medicine registrar at the School of Population and Public Health at the University of Melbourne, also said the asymptomatic rate in Shanghai appeared unrealistic.

“It is quite a lot higher than currently what we think in Australia,” he said.

Dr Szanyi estimated that on current evidence the asymptomatic rate of Omicron in Australia and around the world was between about 33 and 50 per cent.

In a study published late last year in the peer-reviewed journal JAMA Network Open, researchers analyzed data from 77 previous studies involving nearly 20,000 people who had been diagnosed with COVID-19.

They found only about 40.5 per cent of confirmed infections were asymptomatic.

Dr Szanyi said the way Australia counted cases was straightforward.

“In very simple terms, an asymptomatic case is simply a case of COVID-19, in which that person isn’t displaying symptoms,” he said.

“From an Australian perspective, we are accounting for people who have positive test results, even if they don’t have symptoms, as cases.”

A man standing in front of a white wall.
Dr Joshua Szanyi says all positive results are counted as confirmed cases in Australia regardless of symptoms.(Supplied)

What is behind such a high asymptomatic rate in China?

China has been questioned over its definition of asymptomatic, which differs from the World Health Organization.

Chinese state-owned media outlet CCTV published an explainer earlier this month on the difference between asymptomatic and confirmed cases.

It said an infected person with a positive test result “cannot be considered as a confirmed case” if they don’t have symptoms “such as fever, dry cough, exhaustion, sore throat, loss of smell [taste]diarrhea, and there are no features of pneumonia on CT imaging “.

The Shanghai Municipal Health Commission has published a similar definition in March.

A man standing in princess park, Melbourne, Australia, smiling to the camera.
Dr Michael Toole says the rate of asymptomatic cases in China is “not normal”.(Supplied)

Dr Toole said using a CT scan to define a confirmed case was particularly concerning.

“CT scans may not detect any change, even if the person has an active virus in the upper airways,” he said.

“The only time you would get a CT scan would be if you presented to an emergency room with symptoms, or you were admitted to hospital.”

The ABC has contacted the Shanghai Municipal Health Commission for further comment on how it counts cases and defines asymptomatic.

The credibility of China’s official case numbers has been questioned since the outbreak emerged in Wuhan in 2020.

A study published in late 2020 by the country’s official Center for Disease Control and Prevention found more than 4 per cent of survey participants from Wuhan had COVID-19 antibodies in their blood.

Based on Wuhan’s population it means nearly 500,000 people may have contracted COVID-19 – 10 times greater than official data.

Two men look through empty deli shelves at a supermarket in Shanghai,
Shanghai residents are facing food shortages.(AP: Chen Si)

Dr Toole said he believed Chinese authorities were confusing asymptomatic cases with pre-symptomatic cases.

“When you go out and you test a whole population, you’re going to pick up a lot of people who just got infected, and they haven’t developed symptoms yet,” he said.

“But they may go on to develop symptoms.”

Back at Ms Yang’s apartment, the anxiety about case numbers and food shortages continues.

“We need supplies, especially food, such as vegetables, milk, fruits, and so on,” she said.

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