The most popular messaging app, Tencent-owned WeChat, has been censoring keywords about coronavirus since January 1st.

The chat conversations were sent from one of the Canadian WeChat accounts to the Chinese one. They observed which messages the Chinese account got. 132 keywords were censored in January, but that number rose to 516 keywords by the second week of February.

Yy’s blacklist is in the app itself, unlike WeChat’s, which uses a remote server for censorship. Five of those keywords were removed on February 10th.

Public health officials from China first informed the World Health Organization about the virus at the end of December. Wechat has a monthly active user base of over one billion people. A lot of users may have missed important information about the coronavirus, as well as how to prevent its spread.

Li wenliang was among the earliest to warn the population about the disease. His story created public outcry against the government’s handling of the coronavirus.

Wechat has close ties with the Chinese government. The government has already used WeChat and Twitter to track down people Chinese officials felt were sharing negative information about the coronavirus outbreak.