As Indonesia’s most populous province weighed tough movement restrictions to stop the new coronavirus, it turned to a loosely-knit volunteer group of data scientists and health experts. The Kawal COVID-19 (Guard against COVID-19) group organized a data model presented to the provincial governor that showed there could be 70,000 deaths by July in West Java if no restrictions were imposed compared with only 20,000 if it took tough action. West Java province locked down. “They were keen to provide help and we accepted it,” said Ridwansyah Yusuf Achmad, an adviser to the West Java governor who organised the online meetings with Kawal volunteers and praised the group as patriotic for donating its expertise. He, and other West Java officials, said the modelling from Kawal had swung the argument. In the face of patchy data and conflicting advice from Indonesia’s central government over measures to fight coronavirus, Kawal’s 800 volunteers have emerged as an increasingly important source of information and guidance. President Joko Widodo’s government has been reluctant to impose travel bans and other measures that could damage the economy in the world’s fourth-most populous country, a 5,000-km (3,100-mile) wide archipelago. Kawal has set out a clear argument for tougher action in the Southeast Asian country with the biggest death toll in the region by far. Pandu Riono, an epidemiologist at the University of Indonesia who is part of Kawal, presented the data to officials in West Java, home to over 50 million of Indonesia’s 270 million people. “West Java had the highest risk of transmission among Indonesian provinces,” he said. “We recommended a wider lockdown.” On May 20, West Java Governor Ridwan Kamil proclaimed the speed of transmission had been cut to a third and that the “curve had flattened”. The president’s office, the health ministry, and the communications ministry referred questions on Kawal to the presidential task force on COVID-19. However, Achmad Yurianto, the spokesman for the task force, told Reuters he had never heard of the group. The government, he said, has taken appropriate measures in fighting the virus. “This is learning by doing. We’ve never had an experience in handling COVID, right?” Yurianto said.