A blue flu is a type of strike action undertaken by police officers in which a large number simultaneously use sick leave.
[1][2][3][4] At times, the matter goes to court,[5] such as when officers need to undergo medical examination to prove genuine illness.
[6] A 2019 opinion piece in The New York Times contrasted blue flu with a strike, calling it "a quiet form of protest, with no stated principles or claim for public attention or sympathy.
The idea of the Blue Flu was referenced in the Babylon 5 episode By Any Means Necessary in 1995, with respect to a labour strike.
"Barney Miller", a sitcom about NYPD detectives in a Greenwich Village precinct, ran a two-part Blue Flu episode called "Strike" in March 1977.