Employers have long worried about workers who call in sick so they can surf or watch TV. Now some experts say companies should pay attention to the flip side of that problem: employees who show up feverish and sneezing. They even have a word for this behavior, which can hurt productivity just as absenteeism does: "presenteeism." Though the worry isn't new, it has gained momentum with fears of a bird-flu pandemic. Should the disease mutate into a strain that passes from person to person, public health officials say, it could thrive in offices. "I wish employers would make it possible...