Why China’s Covid case count plummeted when the nation changed its policies

Tam Hunt
6 min readDec 27, 2022


Plummeting case counts are entirely predictable given the end of mandatory mass testing of the Chinese population, and the end of reporting asymptomatic “cases,” because widespread and repeated mass testing of people without symptoms results in huge numbers of false positives (99% or more false positives); so eliminating mass testing entails a dramatic reduction in the number of false positives and equally reduced case numbers

A recent Financial Times article fretted about China’s strangely plummeting case and death counts from Covid after its big shift in policy just two weeks earlier:

China’s official daily Covid case and death counts have plummeted despite the unwinding of the coronavirus curbs, with the country’s health commission reporting just seven fatalities since it announced its relaxation of Covid rules.

However, we know, with a high degree of mathematical certainty, that the vast majority of China’s “cases” before lifting their Covid-zero policies were false positives. This is because they were requiring mass Covid testing, on a regular and repeated basis, of entire city populations (basically the whole country seems to have been testing at least once a week and many twice or tree times a week), and were reporting very high percentages of “asymptomatic cases” in their official case counts.

For example, in early March of 2022, 229,742 positive COVID-19 cases were reported in the locked down city of Shanghai. But only 8,322, or less than 4%, were “confirmed cases” and the rest were 221,420 asymptomatic infections.

Mass testing of entire cities without requiring any symptoms at all as a gatekeeper for testing will necessarily lead to a vast majority of test positives being false positives. I explain the numbers more below but the result of this policy is that the vast majority of these “asymptomatic cases” are simply false positives.

Financial Times also reported on December 14 China’s major change in stopping reporting of asymptomatic cases, but very few have connected the dots between these changes, and the underlying dynamics of what these policy shifts do to the official case counts and Covid deaths.

I worked through the math behind the false positives issue in China in detail in this piece that looked at Shanghai’s case numbers and false positives in April of 2022. The short summary is that well over 99% of Shanghai’s “Covid cases” at that time were almost certainly false positives. And this is because the actual background prevalence of symptomatic Covid was very low, and when the background prevalence is low, and everyone is subjected to mass testing, the result will be extremely high rates of false positives.

The BMJ Covid test calculator shows that even a test with 98.9% specificity in the lab will result in 99.9% false positives (99,960 out of 100,000 false positives) when the actual disease prevalence (pre-test probability) is only 0.04%, as it was in Shanghai in April of 2020

Don’t believe me on the severity of the false positives issue? The US FDA warned of exactly this issue in a November 2020 notice that highlighted the math of false positives. FDA wrote that even a test that is 98% accurate in the lab will result in 96% or more false positives in the field when background prevalence is low (0.1% or less). I showed in my essay on Shanghai’s numbers, linked above, that in Shanghai in April of 2022 the actual prevalence of the disease was no more than 0.04%.

A very large part of what is going on in China is the same as happened in US and other countries with the shift to home antigen test use and a move away from PCR tests. And this shift to home antigen tests entails, yes, the entirely predictable extremely high rate of false positives as people use these highly flawed tests often when no symptoms are present.

So China went from not allowing antigen tests to count for official use (even though they were approved for use back in March of 2022 by the authorities, but only PCR tests counted and these were mandatory and frequent for all people in China until recently), to now encouraging home antigen test use and self-quarantine if a positive test results.

A Washington Post article explained the policy on antigen tests right before China’s shift away from PCR tests to antigen tests:

Along with requirements to regularly visit PCR testing booths — at-home antigen rapid tests are not officially recognized or widely used — these apps were among the most prominent features of zero covid life in China.

And as in the US and most other developed nations, with the shift toward home antigen testing and away from PCR and mandatory testing, these test results are not being tallied in official data.

So in China what we’re seeing now is removal of a policy that had resulted previously in 99% or more of the “Covid cases” being false positives. Halting the policy of mass testing will inevitably lead to elimination of these 99% or more of the “cases” in the official case counts. At the same time, we’re now seeing vast numbers of false positives in home antigen test kits that are panicking people and resulting in growing distrust of the official numbers.

Mystery solved (I’ll send the invoice later).

WHO and all the other critics of China’s data can sleep a little better now.

But let’s not stop here on our journey, because almost all experts acknowledge now that the case numbers themselves don’t matter that much — what matters far more are hospitalization and death numbers. I’ll focus only on the death numbers in what follows.

China is using a different definition of a “Covid death” than WHO or most other countries like the US, but China’s definition of a Covid death is light-years more reasonable than the US or WHO’s definition.

China clarified in early December that its definition of a Covid death only includes those who die from pneumonia or other respiratory failure and test positive for Covid. There is still no causal linkage required in terms of establishing that Covid actually caused the death at issue.

Many nations and US states are now defining a Covid death (see the link for original sources) as anyone who dies within 30 days of a positive PCR test. Yes, that’s all that is required — no causal linkage is required between Covid and the death. And it isn’t even required that the person had Covid — just a positive test result. This video compiles many public statements from public health officials on how they defined “Covid death.”

So this “Covid death” definition is absurdly over-inclusive, designed to sweep any possible hint of Covid being involved or associated with a death, and is blatantly less stringent than equivalent definitions of a vaccine-related death or a “breakthrough Covid death” (defined as someone how is fully vaccinated but still catches Covid and dies from it).

The definition of a Covid death in western nations is a very large part of how the pandemic death numbers in western nations (US, EU, Australia, New Zealand, in particular) have been so much larger than China and, for example, African nations — reversing rather starkly the usual pattern with infectious diseases where poorer nations suffered noticeably more with previous infectious disease outbreaks.

The fact that richer nations suffered far higher rates of harm during the Covid pandemic is a significant clue that something screwy has been going on. And that screwy something has been both absurdly over-inclusive definitions of “case,” “hospitalization,” and “death,” but also policies like mass testing of asymptomatic people (also known as “screening” as opposed to “diagnostic testing).



Tam Hunt

Public policy, green energy, climate change, technology, law, philosophy, biology, evolution, physics, cosmology, foreign policy, futurism, spirituality