Nearly half of the United States is reporting widespread seasonal flu, according to a report released by the Centers for Disease Control and Prevention last week. Twenty-five states reported widespread geographic influenza activity, an increase from ten states in the previous week. To date, the most common virus has been H1N1, also known as the swine flu virus, which caused a pandemic in 2009, spreading from Central Mexico to 74 other countries, causing 284,000 deaths, according to the CDC.

The CDC reports that additional increases across the country are expected in the coming weeks and recommends that anyone aged six months and older—especially pregnant women and those with a high risk of complications—who has not gotten a flu vaccine yet this season, should get one now.

The CDC estimates that flu vaccinations prevented more than seven million illnesses last year, more than three million doctor visits and at least 80,000 hospitalizations.

Visit the CDC’s weekly FluView report for more information.