Note: As unusual as this year’s flu season has been with the earliest onset in 16 years and the rise of B strains that haven’t been dominant in almost 30 years, A strains are now picking up, according to the latest CDC estimates. The recent spike in A-strain illnesses is increasing the odds of a “double-barreled flu season,” an extremely rare pattern in which two types of flu strike back to back, meaning people could get both types of flu this year. Infectious disease experts insist it is not too late to get vaccinated, especially because the current vaccine only covers about 58% of B-linked cases but covers A strains well.