After an early start to the flu season, Arizona health officials have declared the illness in the state as widespread, which is the highest category possible.
Influenza has been reported in 14 of the 15 counties, according to the Arizona Department of Health Services. [Related: Influenza surveillance reports from DHS]
More than 2,200 cases have been reported since the flu season began, according to a DHS spokesperson, and more than 1,000 in the past week alone. The state has confirmed 283 of those cases as flu.
Visits to the doctor for flu or flu-like illnesses have steadily increased during the last few weeks. There's also been an increase in hospital admissions, especially in the central part of the state.
However in the Phoenix-Metro area, emergency rooms are reporting a relatively low number of flu cases.
Banner Health said it has seen more viral illness in general and is prepared for an uptick in flu cases as we get deeper into flu season.
St. Joseph's Hospital tells CBS5 they are treating more patients for the flu, but their emergency room is not overwhelmed.
While Arizona typically sees most of its flu cases in February or March, the flu can be unpredictable and can peak either earlier or later in the season.
"The flu season started early," said Dr. Robert Fromm, chief medical officer for Maricopa Integrated Health System, which includes Maricopa Medical Center. "It's kind of taken off. So, our expectation is that at least as we move further into the flu season - we will be inundated in the ER."
About 1,000 cases of the almost 2,200 Arizona has had this season were reported last week. However, because many people are not tested for the flu, those figures are likely just a fraction of the true number of cases, state health officials said.
There's a new flu vaccine each year, based on the best guess of what flu viruses will be strongest that year. This year's vaccine is well-matched to what's going around. The government estimates that between one-third and one-half of Americans have gotten the vaccine.
But the vaccine isn't foolproof, and even those who were vaccinated can still get sick. At best, the vaccine may be only 75 percent effective in younger people and even less so in the elderly and people with weak immune systems.
Health officials are analyzing the vaccine's effectiveness, but early indications are that about 60 percent of all vaccinated people have been protected from the flu. That's in line with how effective flu vaccines have been in other years.
Fromm recommends getting the flu shot if you haven't already.
"This epidemic actually occurs over time," he said. "So, if you have yet to come into contact with influenza, you haven't had influenza - there is still an opportunity to go ahead and get your immunization. You shouldn't decide not to do it just because it's already January."
On average, about 24,000 Americans die each flu season, according to the CDC.
Flu usually peaks in midwinter. Symptoms can include fever, cough, runny nose, head and body aches and fatigue. Some people also suffer vomiting and diarrhea, and some develop pneumonia or other severe complications.
Most people with the flu have a mild illness and can help themselves and protect others by staying home and resting. But people with severe symptoms should see a doctor. They may be given antiviral drugs or other medications to ease symptoms.
Fromm advises visiting your regular doctor or an urgent care center before heading to an ER.
"Every person that comes in with uncomplicated flu to the emergency department, means a delay for someone who may be having a heart attack or more serious illness," he said.
However, Fromm said if you have trouble breathing, don't hesitate to visit the nearest ER.
The last bad flu season involved a swine flu that hit in two waves in the spring and fall of 2009. But that was considered a unique strain, different from the regular winter flu.
Copyright 2013 CBS 5 (KPHO Broadcasting Corporation). All rights reserved. The Associated Press contributed to this report.