A report published by the University of Toronto’s Citizen Lab on Tuesday charged the Chinese government with heavily censoring news and discussion of the coronavirus outbreak beginning at the end of December.

The report noted that China’s broad censorship practices could “restrict vital communication related to disease information and prevention.”

The timing of China’s censorship is crucial, as the last week of December was the period when whistleblower doctors in Wuhan began warning colleagues about an epidemic the government refused to acknowledge.

The most famous of those doctors, Li Wenliang, was arrested and threatened for spreading “false rumors,” remodeled as a hero of the Communist Party once the existence of the Wuhan virus could no longer be concealed, and killed by the virus at the beginning of February – at which point the Communist Party tried to conceal his death for as long as possible.

The Citizen Lab report detected the beginning of large-scale censorship on the popular YY live-streaming and WeChat messaging platforms based on keywords and phrases related to the virus at the end of December. Blocked content included “criticism of the Chinese government, speculative and factual information related to the epidemic and neutral references to Chinese government efforts to handle the outbreak that had been reported on state media.”

The information control effort went far beyond blocking chat-room discussions that made Chinese officials uncomfortable. Censorship and intimidation are intensifying even as the Chinese government claims the epidemic is coming under control:

Government briefings and media reports show that the Chinese authorities delayed releasing information on the epidemic to the public. When eight individuals (at least two of which were medical experts) tried to warn the public of the then mysterious outbreak on December 30, 2019, they were silenced and punished by local authorities in Wuhan for “spreading rumours” and “disturbing social order.” On Feb 5, 2020, the Cyberspace Administration of China (CAC), the top-level Internet governance agency in China, issued a public statement stressing that it would punish “websites, platforms, and accounts” for publishing “harmful” content and “spreading fear” related to COVID-19. The CAC singled out Sina Weibo, Tencent, and ByteDance in the statement, saying that it would carry out “thematic inspection” of their platforms. Chinese authorities continue to warn the public of the consequences of “spreading rumours.” A non-comprehensive collection of police announcements on the punishment of “rumour-mongers” shows that at least 40 people were subject to warnings, fines, and/or administrative or criminal detention around January 24 and 25, 2020. Another announcement points to a much larger number, detailing 254 cases of citizens penalized for “spreading rumours” in China between January 22 and 28, 2020.

Of particular interest to those considering commercial and technical relations with Chinese companies is Citizen Lab’s observation that much of the censorship was performed by nominally “private” corporations such as Tencent, the owner of WeChat. Long before government censors begin stepping in to delete posts the Communist Party doesn’t like, Chinese corporations are searching for blacklisted phrases and automatically suppressing messages that pass through their servers.

Citizen Lab’s researchers demonstrated this by sending identical messages through U.S. and Canadian accounts versus Chinese accounts. Messages containing blacklisted phrases were instantly blocked without warning or notification when they passed through the Chinese account – recipients simply never saw the messages or knew they had been sent.

Mentioning Chinese President Xi Jinping, other top Communist officials, or Dr. Li Wenliang in the same message as the coronavirus proved to be a reliable formula for getting messages blocked. Another good way to get a message flushed down the censorship toilet was to discuss how Taiwan, Hong Kong, or Macau has responded to the virus epidemic.

A great deal of the messages Citizen Lab saw blocked during their testing contained factual information about the coronavirus, including techniques for avoiding infection.

“Since the outbreak, government officials and Party leaders have been stressing the importance of ‘public opinion guidance’ and ‘leadership over news and propaganda.’ Limiting the dissemination of speculative information about the disease may be an attempt to reduce public fear, for example. On the other hand, censoring keywords critical of central leadership and government actors may be an effort to avoid embarrassment and maintain a positive image of the government,” the University of Toronto report noted.

One especially ugly smoking gun revealed by the report was that early examples of keyword censorship were detected several weeks before the Chinese government admitted the Wuhan virus could be passed between humans.

This “strongly suggests that social media companies came under government pressure to censor information at early stages of the outbreak,” researchers noted. It also means information that could have helped Wuhan residents avoid the coronavirus was suppressed by their government, and it wasn’t the work of a few misguided local goons in the Wuhan city government, as the national Chinese Communist Party has claimed.