Since January, more than 13,000 people have died of complications from seasonal flu, according to the Centers for Disease Control and Prevention’s weekly report on the causes of death in the nation.

No fewer than 800 flu-related deaths were reported in any week between January 1 and April 18, the most recent week for which figures were available.

The report looks at deaths in the 122 largest cities in the United States.

Worldwide, the annual death toll from the flu is estimated to be between 250,000 and 500,000.