Health officials are busy warning anxious citizens about the spread of the H1N1 virus, better known as the swine flu. For their part, organizations are advising their employees on how to keep their illnesses to themselves. Internal emails describe everything from how to properly cough in public (seems it's better to cough into the crook of your arm than into your hand) to how soon to return to work after experiencing the flu (wait at least until the fever subsides).

If only companies were as concerned about the contagiousness of their leaders' emotions.

Even without speaking, leaders can communicate their moods to everyone around them. And, as researchers Howard Friedman and Ronald Riggio established, emotionally expressive people can nonverbally transmit their moods onto others almost immediately.

Friedman and Riggio studied three-person groups comprised of one highly expressive subject and two unexpressive participants. Subjects in each group sat facing away from each other while completing a mood questionnaire. Participants then turned and faced their fellow group members for two minutes, during which time they could look at each other but not speak. Finally, participants filled out another mood survey.

As the researchers had expected, the moods of the unexpressive subjects tended to change to match the mood of the highly expressive participants. For example, an angry, highly expressive subject could make two happy, unexpressive people irate. In two minutes or less! All without saying a word.

As Friedman and Riggio point out, nonverbally expressive individuals broadcast their feelings through their body language, and those around them cannot help but notice the signals. Negative emotions are especially easy to transmit nonverbally, because people are naturally receptive to warnings about anxiety, fear, and anger.

Emotions, like a flu virus, are contagious. If you're a leader, be aware that you might be silently infecting your employees with your nonverbal messages. Try spreading some positive messages instead.