Two Utahns have died after testing positive for the H1N1 swine flu, health officials confirmed Sunday, bringing the number of deaths linked to the illness in the state to four.

Utah is the only state in the Intermountain region with flu-attributed deaths; it has more confirmed cases of the H1N1 than any of its neighboring states, according to data from the Centers for Disease Control and Prevention.

The new cases involved Salt Lake County residents between the ages of 25 and 50, said Pam Davenport, a spokeswoman for the Salt Lake County Valley Health Department. One died Friday and the other, a woman, died Saturday. Davenport said one of the adults had underlying health problems.

Cyndi Bemis, a spokeswoman for the Utah Department of Health, confirmed the adult who died Saturday was a woman but said she did not know if underlying health problems were a factor.

A family member identified the woman as Francine Rushton, 47, and said she contracted the flu about two weeks ago but was initially told it was not the H1N1 type, despite her mother's diagnosis with H1N1 that week.

"She tested negative, so they sent her home and told her to get fluids and rest," said Craig Whitehead, Rushton's brother. Because her mother's health had improved on Tamiflu, the family "begged them to administer Tamiflu" to Rushton, Whitehead said. Doctors said they would not without a positive flu test.

Rushton's third test came back positive, more than a week after she first fell ill, Whitehead said.

"By then it was too late," White he said.

Rushton's family is urging flu patients to be vigilant about their symptoms and assertive in seeking treatment.

"Don't take it lightly," Whitehead said. "I sat at work three weeks ago and scoffed, 'What's the big deal?' ... Now I feel differently about it."

There have been 688 confirmed cases of the flu in Utah, including 25 cases among health care workers. A majority of those diagnosed with the virus in Utah have been between the ages of 5 and 24.

H1N1 has spread so quickly that last week the state announced it would stop tracking the number of confirmed cases. Health-care providers can assume that any patient who tests positive for influenza A strain has H1N1, and can begin treatment with antivirals, officials said.

The state will continue to track the numbers of patients who are hospitalized. As of Thursday, 90 people in Utah had been hospitalized with the flu.

Nationwide, there are 17,855 confirmed cases and 45 deaths from H1N1 in the U.S., according to the Centers for Disease Control and Prevention

Confirmed cases in neighboring states stand at 597 in Arizona, where five deaths have occurred; Nevada at 162; New Mexico at 155; Colorado at 75; and Idaho, 29.

The first two Utahns who died from the flu both had health problems. One was a child between the ages of 5 and 18, the other was 21-year-old Marcos Antonio Sanchez.

Reporters Erin Alberty and Lindsay Whithurst contributed to this report.