Few experts in the world know more about Asian epidemics than Dr. Luke Lucas and his microbiologist wife, Lynn. But as a stream of new patients travel from the same city in Uzbekistan to the emergency room at University Hospital in San Francisco, each hopes for a miracle that the doctors are not sure they can deliver.

As the hospital's capacity is tested with patients battling tuberculosis caused by microbes resistant to all antibiotics, other victims wander the city, coughing amid crowds of people and creating a public health disaster. Now forced to battle against the complacency of...