Term for an unofficial police strike where officers call in sick en masse to protest any number of possible issues - wages, administration, actual criminal persecution of corrupt cops, whatever. The collective use of sick days is sometimes necessary due to laws banning police strikes, although police unions may also use them to gain an advantage in any future bargaining. Unlike most strikes, blue flus are usually fairly short-term. They may not be as universal as most labor disputes, due to a lack of the traditional blue-collar prejudice against scabs and the existence of police with a sense of duty towards law enforcement. One can imagine that blue flus don't exactly endear the police to the general populace or the local government, and some police contracts ban them as well as striking.

While the term most accurately describes police strikes, it has also been applied to other public employees, such as firefighters and teachers (who also have the amusing term chalk flu). A similar act by other groups is better described as a sick-out.

For one example of a blue flu in action, see The Blue Flu.

The source of the term obviously comes from the stereotypical American blue police uniform and one of the most common reasons for missed employment - influenza.