COLOMBO — In scientist Wei Yuansong's office drawer is a thank-you letter written in Sinhalese and signed by an entire Sri Lankan village.

The letter, which passed through many hands and was franked in different locations, contains the shared memories of a decade-long fight against a killer kidney disease that had plagued villagers for years because of their lack of safe drinking water.

"We express our heartfelt gratitude to Professor Wei for providing us with safe and tasty drinking water," the residents of Nildiya village wrote.

Now director of the Laboratory of Water Pollution Control Technology at the Chinese Academy of Sciences, Wei says that his connection to Sri Lanka began in August 2013, when he received an email from Dr S.K. Weragoda about collaboration on water treatment to address Chronic Kidney Disease of Unknown Etiology.

At the time, CKDu was a major public health issue in Sri Lanka, with over 40,000 people afflicted by the disease since the mid-1990s. In 2016, then Sri Lankan President Maithripala Sirisena referred to it as a "national disaster" that was affecting 20,828 patients and causing 5,000 deaths a year.

Preliminary research by the World Health Organization indicated a strong correlation between CKDu and groundwater pumped for drinking, and correspondence with Sri Lankan scientists brought the issue to the attention of Chinese counterparts.

In August 2014, Wei made his first visit to Sri Lanka to undertake an arduous research journey with Weragoda. Each day, they traveled for hours along bumpy roads deep into the affected areas, and paid home visits to villagers.

They were greeted with cold shoulders and doubts. "Many local residents thought that the Chinese, like others (foreign researchers), were there to write papers, not to genuinely help them," Wei says. The two scientists had to negotiate difficult conversations to win their trust, but were eventually welcomed to take crucial samples for analysis.

Following preliminary research and extensive coordination between the two sides, a deal was inked in March 2015, enabling joint research into the causes of CKDu and drinking water safety. Since then, Wei has frequented Sri Lanka with other Chinese scientists to conduct thorough research into water treatment solutions suitable to local conditions.

During the following years, the Chinese academy and its partners built four drinking water facilities in Sri Lanka that provide safe drinking water to over 5,000 villagers and more than 1,300 students, and then founded a China-Sri Lanka Joint Research and Demonstration Center for Water Technology in the central city of Kandy.

The center has trained 30 medical workers, 20 kidney disease investigators, 20 water professionals, and 30 graduate students. Two joint CKDu-related research papers by Wei's team won Sri Lanka's President's Awards for Scientific Research in 2023 and 2024.

"Local residents now trust Chinese scientists wholeheartedly. … Villagers with kidney disease say they haven't had to go to hospital for years thanks to the help of Chinese scientists," says Titus Cooray, a PhD student at the JRDC.

This July, Wei attended a joint research workshop at the JRDC on climate change, marine sustainability, and other topics, with participants from nearly 10 countries, including the United States, Canada and the Maldives.

"This is my 31st trip to Sri Lanka. We have laid the foundation from zero to one, and future collaboration will undoubtedly progress from one to infinity," Wei said at the event.

"China has transitioned from being a participant to being a leader in global environmental governance, and we aim to bring more benefits to the Sri Lankan people through scientific cooperation, and to make this project a model of 'Belt and Road' international cooperation," he said.