Boston declared a public health emergency on Wednesday after this year’s strains of the flu virus killed more than 12 people. Arizona, Montana and South Dakota have all reported widespread flu. For those of you keeping count, that brings the total to 44 states. And even crazier still, the Centers for Disease Control (CDC) has reported that that the percentage of people going to the hospital to be treated for the flu symptoms has doubled in the last month. Welcome to to flu season.

Boston Public Health Commission’s executive Director Barbara Ferrer noted that “In the last two weeks alone we’ve doubled our number… So, if we continue at this rate to see new cases, we’ll have an explosion of flu in the city of Boston. We really need to get ahead of it at this point in time.”

So what can people in Boston (and everywhere across the US really) do to help stop, if not slow, the rapid spread of the flu this year? Well the answer is pretty straightforward: get vaccinated. Health officials are urging vaccination for everyone over 6 months of age, and many are giving free shots this weekend.

Read more: National flu outbreak widens