Four western states are the nation's hotspots for flu, and an epidemiologist predicts infections will grow after the holidays as children return to school and adults go back to work.

Arizona, Utah, California and New Mexico report widespread flu infections, according to the Centers for Disease Control and Prevention's weekly flu report. "Widespread" is the CDC's highest designation for flu activity.

"We think the worst is still yet to come," said David Engelthaler, epidemiologist for the Arizona Department of Health Services. The nation's flu season typically peaks in January, February or March.

The number of flu cases is not known. Many patients do not report cases to doctors, and doctors may not test specifically for flu in people who do seek treatment, officials said.

Wait times at some emergency rooms in metropolitan Phoenix are getting longer as flu patients seek treatment, leading some hospitals to rearrange their staffing plans.

Mellissa Voll, 26, said she thinks she caught the bug at a halfway house where she works with recovering drug addicts. But she did not plan to approach flu season any differently in the future.

"If it's free, I'll get a flu shot," Voll said Friday while waiting at an emergency room in Phoenix. "Other than that, no."

She said she does not have health insurance and went to the hospital after over-the-counter drugs failed to relieve her symptoms.

Deborah Busemeyer, spokeswoman for the New Mexico Department of Health, said her state is on par with a typical flu season.

A spot check of a few hospitals in New Mexico found none inundated by patients. But doctors' offices, urgent care centers and some emergency rooms in Albuquerque reported an increase in cases.

In Los Angeles, about 6 percent of visitors to clinics and hospitals reported influenza-type symptoms. That figure was nearly 12 percent in the San Francisco area.

Susan Mottice, a state epidemiologist in Utah, said recent reports indicate the rate of flu activity there is rising. "That means we haven't yet peaked, and we don't know when we'll peak," Mottice said.

At the University of Utah Hospital in Salt Lake City, doctors saw an influx of emergency room patients with flu-like symptoms during the week before Christmas. But the increase was not significantly higher than in busy periods in previous years.

Dr. Art Mollen, who operates two medical offices in Phoenix, said this flu season is far busier than in the past, but most illnesses are mild to moderate.

"We are not to the point where we are overwhelmed," said Mollen, who expects the wave of cases to taper off into a fairly normal flu season.

Glen Nowak, a spokesman for the CDC, said it's not known whether the outbreaks in the West reflect what other states can expect.

"There is no data to indicate it's any different from previous seasons, but we are at the beginning," Nowak said. Other states still have time to catch up, he said.