California public health officials are investigating the possible tuberculosis exposure of nearly 1,000 babies from a Kaiser Permanente nurse, and meanwhile hundreds of worried parents have been flocking to the San Francisco hospital to begin screening tests. Kaiser disclosed that a night-shift healthcare worker in the maternity ward's postpartum unit had developed an active case of tuberculosis. The nurse was a Kaiser employee from March 10 to Aug. 10, and Kaiser learned of the infection Aug. 18. It then began notifying 960 mothers and 115 employees that they and their babies may have been exposed.