BEIJING－As Beijing embraced the first winter snowfall on Nov 29, Zhou Bo, a volunteer who tests people for HIV, was busy in his well-heated downtown office.

"I have already received nine people today, and five more are expected according to the reservation system," he said. Zhou said about 10 to 15 often show up for HIV tests on workdays, and 20 to 30 on Saturdays and Sundays.

He became a volunteer eight months ago when one of his friends was infected with HIV. He had no knowledge of the virus but wanted to help. "I've learned a lot here and helped a lot of people," he said.

The lab where Zhou works belongs to a nongovernmental institution working in AIDS control and prevention in China. It also operates Blued, one of the country's biggest gay dating apps. The location-based app allows anyone to make an anonymous appointment for a HIV test.

Blued has nearly 40 million registered users, 60 percent of them in China.

Zhang Dapeng, deputy president of the company's health section, said online communities can play an important role in voluntary testing for HIV.

"Blued's anonymous reservation and testing service can reach certain groups that are difficult to reach through traditional means, and is more efficient and convenient," he said.

Zhang used to work for the city's health and disease control department. He said Beijing has four labs, which offered free testing to 8,000 people last year.

Gao Fu, head of the country's disease control and prevention center, said China has made significant progress in AIDS prevention and control, especially in recent years.