A community worker in Hangzhou, capital of Zhejiang province, checks a resident's health code using a smart phone. The code is part of local efforts to use big data in the fight against novel coronavirus. (Photo by Dong Xuming/For China Daily)

As millions of Chinese immigrant workers started to return to work in March, Chongqing, Sichuan and Guangdong have agreed to accept each other's health code system to facilitate the safety and convenience of those journeys, according to cqnews.net.

Chongqing and Sichuan in Southwest China are the major migrant labor sources for Guangdong's manufacturing industries.

By the end of February, nearly 2 million workers had left Chongqing to work in other places.

The QR code system is based on the self-declared data of citizens or migrant workers, and integrates with existing epidemic prevention information in China to generate a personal QR code for each applicant.

Over 100 cities and provinces in China have developed their own health code systems amid the coronavirus outbreak. So far, about 700 million people have their own health code.

To avoid submitting information repeatedly in different regions, the health code systems are expected to be mutually accepted across cities in the country.