That same day, Chinese authorities reported 2,478 new confirmed cases — raising the total global number to more than 40,000, with fewer than 400 cases occurring outside of mainland China. Yet CNN can now reveal how official documents circulated internally show that this was only part of the picture.

In a report marked “internal document, please keep confidential,” local health authorities in the province of Hubei, where the virus was first detected, list a total of 5,918 newly detected cases on February 10, more than double the official public number of confirmed cases, breaking down the total into a variety of subcategories. This larger figure was never fully revealed at that time, as China’s accounting system seemed, in the tumult of the early weeks of the pandemic, to downplay the severity of the outbreak…

One of the more striking data points concerns the slowness with which local Covid-19 patients were diagnosed. Even as authorities in Hubei presented their handling of the initial outbreak to the public as efficient and transparent, the documents show that local health officials were reliant on flawed testing and reporting mechanisms. A report in the documents from early March says the average time between the onset of symptoms to confirmed diagnosis was 23.3 days, which experts have told CNN would have significantly hampered steps to both monitor and combat the disease.