Spreading Virally (IMAGE) Brown University Caption A visualization generated by an agent-based model of New York City's HIV epidemic shows the risky interactions of unprotected sex or needle sharing among injection drug users (red), non-injection drug users (blue) and non-users (green). Credit Brandon Marshall/Brown University Usage Restrictions With credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.