F	Facilities: nursing homes or other long-term care facilities.
L	Likelihood of transmitting influenza to others at high risk: young or elderly individuals with an underlying medical condition that puts them at risk, health care providers, employees in assisted living and other residential facilities, individuals living with a person who is part of a high risk group, etc.
U	Underlying medical conditions: diabetes mellitus, chronic heart or lung disease, pregnancy, cancer, etc.
A	Age: elderly (≥65 years) or children (6 to 23 months).