The 100th joint patrol of the Mekong River by China, Laos, Myanmar and Thailand began in Xishuangbanna, Yunnan province, on Tuesday morning.

It is set to last four days and three nights and cover 620 kilometers of the river.

Four law-enforcement ships left a dock in Xishuangbanna on Tuesday morning. Officers from the four countries will conduct both short patrols and full cruises as part of an effort to prevent the spread of the coronavirus.

Since the establishment of combined patrols in 2011, officers from the four countries have conducted 99 patrols of 56,100 km along the river. It is estimated that the effort has prevented economic losses of as much as 188 million yuan ($28.8 million) for people along the route.

Zhou Jiaxin in Beijing contributed to the story.