Three emerging flu or flulike epidemics are threatening the U.S. The annual flu season has gotten off to an early start with an aggressive variant of Influenza, a large and early outbreak of norovirus or "stomach flu", and the worst outbreak of whooping cough in 60 years, with 42,000 confirmed cases. Boston's mayor has declared a public health emergency due to widespread cases of Influenza. On a national scale, deaths and hospitalizations are still below epidemic thresholds, but experts believe that will change. The C.D.C. continues to advocate getting flu shots, and a spokesman said, "We don't know if the season has peaked yet."