China revised its official death toll for coronavirus on Friday, adding 1,290 to the number of dead. Prior to the change the number of those reported to have died of the virus in China since January was 3,342. Analysts point out that this revision increases the numbers by almost 40%. That’s big. It’s also important because numerous models have relied on China’s numbers since the virus began to spread in order to plan their own lockdowns and mitigation efforts. In short: If China’s death toll was larger early on, and many of those deaths went unrecorded, this has serious ramifications for why things may have turned out so differently in Europe, the US and other countries. It’s not the first time China has revised the way it counts virus cases. In mid-February, China also revised the number of cases it was reporting up by 14,840, which Bloomberg and other media pointed out was a revision by more than 45% of the total cases then reported in Hubei. The explanation at the time was that authorities had “added a new group of patients diagnosed by a different method.” Reports wondered whether this obscured the true scale of the crises. The April revision notes that the number now includes cases of people who “died at home without seeing a doctor or being tested for the virus,” which meant they were not recorded at the time.While the February and April revisions both increased the number of cases and deaths at the time by around 40% respectively, there is another issue that was raised with Beijing’s numbers in early April. CNBC reported that China had also begun to “release data on asymptomatic patients.” It turned out that, as one epidemiologist from Boston College noted “we have been basing a lot of our models and our predictions off Chinese data because it was the first major outbreak.” Yet the numbers that most studies were based off, including the most well known studies at the Imperial College that helped guide western policymakers in March, relied on numbers that are not always based on the same guidelines in different countries. For instance, in China, CNBC noted that “the total number of asymptomatic cases recorded since the outbreak began has not been released.”The Nikkei Asian Review notes that China’s health authorities began regular updates in early April for the asymptomatic carriers. “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 in the world.”How can it be that the country where the outbreak began, which many models predicting what would happen were based of, has data that is different from other countries or has been revised by figures of 40% at key dates? In one sense it shows that China grapples with the same challenges that other countries do in relation to fighting the outbreak. But China also claimed that its approach was successful in February and the World Health Organization encouraged other countries to look to this model. The WHO report on its Joint Mission on Coronavirus Disease 2019 (COVID-19) that it conducted with Chinese authorities between February 16 and 24 concluded that “China’s bold approach to contain the rapid spread of this new respiratory pathogen has changed the course of a rapidly escalating and deadly epidemic.” The WHO held a press conference in late February touting these results. They claimed that the statistics showed that when the team arrived there were up to 2,478 new cases a day and when they had left there were only 409 new cases. “This decline inn Covid-19 cases across China is real.”No other country in the world has ever been able to produce such a rapid decline as China reported. In addition the WHO, basing its findings on this optimistic curve that showed cases rapidly declining to almost zero, waited weeks to declare a pandemic while the virus spread across the world to dozens of countries.This leads to questions about the data that has informed policymakers around the world. Some countries acted early and took this pandemic seriously. Israel is among those countries. The Kingdom of Jordan, the UAE, South Korea, Taiwan, Singapore, Japan, and some other countries put in place rapid attempts to mitigate the spread of the virus or to lockdown their societies. Those who study the data behind the models, such as John Burn-Murdoch’s iconic charts at the Financial Times, look closely at data that are produced by countries around the world. If the countries rely on different methods of counting or don’t report cases, those numbers can be skewed and our understanding of the pandemic will be skewed.Policymakers may have other sources of information. Countries have access to other data that may be gathered through clandestine methods, for instance western intelligence agencies have apparently raised questions about the origin of the virus and what China knew early on, according to new reports at CNN and other media. Those intelligence agencies appear to be mostly connected to the US, Canada or UK and other key members of the “Five Eyes” network, which includes Australia and New Zealand.Regardless of what intelligence services may have gathered, other researchers and officials, such as those in Taiwan, raised the alarm early in January. The Associated Press also reported this week that there are questions about how information was reported within China in mid-January when China’s National Health Commission presented a “grim assessment” of the situation in a teleconference with officials. We now know that those who raised the alarm early were right. Those who presented an optimistic curve that would flatten and then decline in two weeks, as the WHO presented in late February, were mistaken.How will the new cases be factored into charts and predictions. If the analysis of a curve flattening and overall death tolls were based on data that was significantly off in terms of its numbers, for instance 40% changes in number of cases, or number of deaths, or not reporting cases, then that analysis would need to be revised. This will encourage countries that acted early and which were pessimistic from the start. It will also cause those places that have predicted a more rosy outcome to take heed of the new data. The end result however, according to Chinese officials, is that Beijing was able to reduce the number of new cases to almost zero. Today China claims most new cases are from foreign arrivals. China has instituted complex controls, including using hi-tech methods, to trace cases. But overall China’s approach appears successful in the sense that much of the country is open again for business. A symbol of that fact is that Apple has reopened its stores in China while they remain closed elsewhere. The only other cases of an Apple store re-opening is in South Korea, where the Seoul branch reopens this weekend. South Korea, like China, has been very successful at confronting the pandemic.