Increasing global travel and rapid viral evolution continue to fuel the annual flu epidemics, which are constantly mutating. Widespread public health campaigns to vaccinate are able to prevent some infections, but efficacy of the vaccine varies by year depending on the dominant strains of the year. 

Widespread public health campaigns to vaccinate are able to prevent some infections, but the efficacy of the vaccine varies by year depending on the dominant strains of the year.  An estimated 45 million Americans were infected by the influenza virus in the 2017-2018 season resulting in over 800,000 hospitalizations and 61,000 deaths.