Contact tracing is the public health tool that keeps diseases contained. Health workers reach out to those individuals who were exposed to someone who has a contagious disease to monitor their health and to prevent further spread.

More than two dozen passengers left the cruise ship before the outbreak was identified. The race is on to connect with them to monitor their health — and the health of those they’ve interacted with.

(Image credit: lakshmiprasad S/iStockphoto)