BOSTON (AP) — Global health authorities are increasingly using artificial intelligence to track emerging epidemics. But it was human intelligence — especially a network of experts scouring social media — that warned the world about a viral outbreak in China in the final days of 2019. Early warning systems for scanning social media, online news articles and government reports for signs of infectious disease outbreaks have become an important tool for agencies such as the World Health Organization. Some systems, such as the volunteer-led Program for Monitoring Emergency Diseases, rely on human subject matter experts. Others are partly or completely automated.