SAN DIEGO COUNTY -- Health officials released new details Wednesday about the case of a 20-year-old San Marcos woman who was the first person in San Diego County to die after getting swine flu.

They also emphasized that people who might have had close contact with the contagious woman are being identified and treated with anti-viral medication.

On Monday morning, Adela Chevalier's mother took her to Escondido's Palomar Medical Center suffering from severe muscle aches, a cough and a low-grade fever, according to Don Herip, medical director of corporate health for Palomar Pomerado Health. Nurses brought her from her car in a wheelchair, because she was in too much pain to walk, he said.

After developing severe respiratory troubles, despite being put on a ventilator and other aggressive care, Chevalier died shortly before 4 p.m., Herip said.

The young woman first got sick Friday and her condition went downhill all weekend, but she sought no medical attention before her emergency room visit. While it's unknown if earlier care would have saved her, Chevalier's case is a reminder that people should call their doctors for guidance when they develop flu symptoms, Herip said.

"You want to diagnose earlier, rather than wait for complications," he said.

Herip said no patients at the hospital were exposed to the virus, because a nurse sent Chevalier to private room as soon as the woman entered the building.

By mid-morning, a lab test showed that Chevalier probably had the swine flu, and another test confirmed the virus Tuesday.

About 50 staff members at the hospital who had contact with Chevalier were treated with Tamiflu, Herip said. The antiviral medication can decrease the severity of swine flu symptoms in sick people and may kill the virus in the body before it sickens an infected person, county public health officer Wilma Wooten said.

Wooten said Chevalier's family members have all been offered Tamiflu, and county public heath workers on Tuesday and Wednesday investigated whether Chevalier had close contact with anyone else while infectious.

Wooten said the young woman had two jobs, declining to be more specific. Public health staff members have visited both workplaces and have so far not identified anyone who Chevalier had close contact with during her infectious period, which would have started about June 5, Wooten said.

Health officials do similar investigations whenever someone is confirmed with the H1N1 virus, Wooten said. So far, 275 people in San Diego County have been confirmed with the virus.

Nationwide, nearly 18,000 cases of swine flu have been confirmed, and 44 people have died from it, according to the U.S. Centers for Disease Control and Prevention.

Call staff writer Sarah Gordon at 760-740-3517.