What does the term "blue flu" refer to?

The term "blue flu" refers specifically to a form of strike action taken by police officers who call in sick to protest working conditions, inadequate pay, or other grievances. This tactic allows officers to effectively display dissatisfaction without engaging in a formal strike, which may be prohibited by law or department policy. By citing illness, police officers can create a significant impact on law enforcement service levels while avoiding direct conflict with regulations regarding strikes.

The other options mention various aspects of police training, cost management, and wellness initiatives that do not align with the concept of officers collectively expressing discontent through absence due to illness. Thus, the focus on public service disruption through reported sickness is what fundamentally defines "blue flu."