(CNN) -- A man who already had heart problems died last week from what appeared to be complications from swine flu, health officials in Washington state said Saturday.
The death, which has not yet been confirmed by the Centers for Disease Control and Prevention, would be the third in the United States linked to the virus, which health officials refer to by its clinical name, H1N1.
"This death is tragic. Our thoughts are with all those affected by this man's passing," Gov. Chris Gregoire said in a written statement. "It's a sobering reminder that influenza is serious, and can be fatal. I know our public health agencies are doing everything they can to track and monitor this outbreak and to protect the people of our state."
The U.S. number of confirmed H1N1 flu cases increased to 2,254 by midday Saturday, an increase of 615 patients since Friday, according to the CDC.
The cases are in 43 states and Washington, D.C. The states with the five highest tallies are Illinois, 421; Wisconsin, 317; New York, 190; Arizona, 182; and California, 171.
The flu strain, which originated in Mexico, killed dozens of people there, causing U.S. officials to worry that it could take a similar toll after spreading across the border. But it has thus far acted similar to typical seasonal influenza -- which usually can be treated successfully but can be deadly among the very old, very young and people with pre-existing health problems.
Washington officials said the man who died in Snohomish County in northwest Washington, was in his 30s and had "underlying heart conditions."
The two other U.S. deaths were in Texas -- a Mexican toddler who was visiting with her family and a pregnant woman who had been on life support since April. Both had several pre-existing medical problems.