disease control showing the flu has reached an epidemic level in the united states. one of the strains making people sick this season has mutated, causing this year's vaccination to be less than optimal for protection. >> the most common virus we're seeing causing disease is this h3n2 virus. when we've seen h3n2, it's widespread. >> reporter: it's being felt widespread. reaching peak levels. >> i was on a ship the other day, i saw about 35 patients. i saw ten positive flu. there were a couple i didn't even swab. i just treated them because it's so prevalent. so we're definitely seeing a lot. >> reporter: the cdc is set to release its latest figures on how widespread the flu bug has become this coming monday. in the meantime, officials still