China's toilet upgrade campaign on World Toilet Day(1/9)

Photo taken on Jan. 15, 2018 shows a toilet in Taizhou, east China's Zhejiang Province. (Xinhua/Sun Jinbiao)

World Toilet Day is celebrated on November 19th every year. This year's theme is "Leaving No One Behind."

More than four billion people, which is more than half the global population, live without safely managed sanitation, according to data from the United Nations.

China launched the "toilet revolution" in 2015 to increase the number and sanitation of toilets at tourist sites. The campaign has been expanded to improve public toilets in cities and build better private toilets in rural areas.

Check how China's "toilet revolution" leaves no one behind:

Villager Lu Yali cleans the toilet at home in Luojiawan Village of Yan'an City, northwest China's Shaanxi Province, June 26, 2018. (Xinhua/Tao Ming)

Students walk past the newly-built flush toilet at a primary school in Zhijin County, southwest China's Guizhou Province, Oct. 23, 2018. (Xinhua/Zhang Yuwei)

Photo taken on Dec. 5, 2017 shows a public toilet in Xijiang Qianhu Miao Village in Leishan County, southwest China's Guizhou Province. (Xinhua/Cai Xingwen)

A worker arranges a mother-and-baby room at a toilet on Xiamen Road in Suqian City, east China's Jiangsu Province, June 26, 2018. (Xinhua/Ji Chunpeng)

A work staff member introduces the baby-care table inside a public toilet on Hongta West Road in Kunming, capital of southwest China's Yunnan Province, May 16, 2018. (Xinhua/Hu Chao)

The interior of a toilet for disabled people on G80 express train is pictured during a trip to Beijing, capital of China, Dec. 22, 2012. (Xinhua/Chen Yehua)

Photo taken on Dec. 5, 2017 shows a gender-neutral restroom in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Visitors look at unisex toilets at the 2018 Chinese Toilet Revolution Innovation Expo in east China's Shanghai, Nov. 18, 2018. (Xinhua/Fang Zhe)