CNN) — There had been no confirmed deaths in the United States related to swine flu as of Tuesday afternoon. But another virus had killed thousands of people since January and is expected to keep killing hundreds of people every week for the rest of the year.

That one? The regular flu.

An outbreak of swine flu that is suspected in more than 150 deaths in Mexico and has sickened dozens of people in the United States and elsewhere has grabbed the attention of a nervous public and of medical officials worried the strain will continue to mutate and spread.

Experts are nervous that, as a new strain, the swine flu will be harder to stop because there aren’t any vaccines to fight it.

But even if there are swine-flu deaths outside Mexico — and medical experts say there very well may be — the virus would have a long way to go to match the roughly 36,000 deaths that seasonal influenza causes in the United States each year.

“That happens on an annual basis,” Dr. Brian Currie said Tuesday. Currie is vice president and medical director at Montefiore Medical Center in Bronx, New York.

Since January, more than 13,000 Americans 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.