The WeChatscope project tracks posts that have been deleted from public accounts on WeChat.Credit: Zhang Peng/LightRocket via Getty

The controversial topic of the first babies born from gene-edited embryos was one of the most censored on Chinese social media last year, according to researchers at the University of Hong Kong.

On 11 February, media researchers Marcus Wang and Stella Fan posted an article to the news website Global Voices in which they describe a censorship project they are part of called WeChatscope.

WeChatscope, they say, tracks articles that have been deleted from 4000 public accounts on WeChat, China’s most popular social-media platform, which has an average of 500,000 users a day. The project preserves deleted posts in a database.

Wang and Fan say the team carried out an analysis using a computer program to scan roughly 11,000 articles that had been censored in 2018 for common keywords, which they used to create a list of the top ten most sensitive topics.

Internet censorship in China is extensive. Private companies and government officials block articles that breach the country's rules. Many companies also have their own teams that censor their own content.

A spokesperson for the project told Nature that gene-edited babies became a censored topic just a day after Chinese biophysicist He Jiankui announced that twins had been born from gene-edited embryos in China.

By far the most censored topic was the US-China trade war. Other topics in deleted posts include local and international politics, a physician jailed for criticizing traditional Chinese medicine, a major vaccine scandal, and allegations of sexual harassment against a professor at Peking University in Beijing.

Most of the deleted posts were replaced with a notification that said the post had been removed “for violation of related law and regulations”, say Wang and Fan, meaning that government censors or WeChat’s internal censorship team considered the contents to be breaching censorship laws.

Some posts were removed by the users who had uploaded them. This is a common occurrence on WeChat because people can be charged with spreading rumours if their post is reposted more than 500 times, write Wang and Fan in the article.

In their article, Wang and Fan wrote that censored topics in China had “expanded from domestic policies and social unrest to less politically sensitive topics, in what seems to be an effort to support China’s international political image as a ‘great power’.”

The case of the gene-edited babies seemed to embarrass the country, and the topic was censored in online news articles as well as WeChat posts.

A Chinese state media report boasting of He's accomplishment as “a historic breakthrough” was removed after international scientists condemned the work. Articles describing He’s past achievements in genome sequencing were also removed from government websites.