The county health department says the victims were a two-year-old Lower Merion boy, a 32-year-old Upper Merion woman and a 24- year-old Norristown man.
Most of the flu confirmed this winter has been the B-strain, not the A-type H1N1 which caused so much illness in 2009 and 2010.
The department is advising county residents to get vaccinated, if they haven't already.
Department director Dr. Joseph DiMino says, "The flu season can continue until May."
It is offering flu shots free to county residents, on a walk-in basis at department clinics.
Individuals with underlying, chronic health conditions are at an increased risk for complications from influenza, and vaccination is especially important.
Symptoms of flu include fever, cough, and often, extreme fatigue. Sore throat, headache, muscle aches, and a runny or stuffy nose are also often present.
To locate a health department clinic in your area, check at www.health.montcopa.org.