The incidence of influenza in Iowa and Illinois is skyrocketing, said state public health officials who stress that there still is time to get vaccinated against the disease.

The two states are among 41 listed as having “widespread geographic spread of influenza” by the Centers for Disease Control and Prevention,

The strain of the flu that is circulating around the country has proven to be a more severe strain, said Melaney Arnold, a spokeswoman for the Illinois Department of Public Health.

“We are definitely seeing more hospital admissions to ICUs (intensive-care units) and some ICU deaths for flu-related illnesses,” she said Tuesday.

There is no reason to think flu activity will decrease anytime soon in Iowa, said Dr. Patricia Quinlisk, the medical director of the state Department of Public Health.

“I think the numbers will continue to go up,” she said, adding that hospitalization numbers and medical clinic visits both have increased recently around Iowa.

More than 150 people were hospitalized for flu complications in Iowa during the last week of December. The state health department said public health officials did not record any flu hospitalizations during the corresponding week in 2011.

Arnold said almost 150 people around the state have been admitted to hospital intensive-care units with the flu this season and that six have died. Eight Chicago-area hospitals turned away ambulances Monday night as they dealt with a surge of patients reporting flu-like symptoms such as cough, fever, muscle aches and runny nose.

Some 5 percent of people being seen in clinics end up having influenza, but many people do not go to a doctor when they become sick, officials said.

Influenza quickly can become a serious illness. The flu, complicated by pneumonia, is one of the top-10 causes of death in the state, Quinlisk said. “It’s the only infectious disease in the top 10, and it still causes a high amount of deaths in Iowa,” she added.

Influenza activity at Trinity Regional Health System has about doubled in the past month. In all of Trinity’s emergency departments, there were 35 cases of influenza-type illnesses recorded in the past week. Six people with influenza were admitted to its hospitals in Moline, Rock Island and Bettendorf.

During the week of Dec. 18, there were 19 cases in the Trinity emergency departments and two people were admitted to its hospitals.

Genesis Health System had four patients confirmed with the flu and admitted to its hospitals in the past week. Some patients who have been critically ill with influenza have been treated at Genesis, infection prevention coordinator Lisa Caffery said. The majority of the patients seen in Genesis emergency departments are treated and released, she added, and that is also the case with patients visiting physician offices.

The good news, health officials said, is that there is still time to get vaccinated and be protected for the rest of the influenza season. Even if a person already has the flu, a shot would help protect them against the three strains that are circulating the nation, Quinlisk said.

The vaccine, she added, is a very good match for the strains. She urged people who are around the most susceptible populations — very young children and the elderly — to seek protection by getting inoculated.

While it takes about two weeks to develop immunity to influenza, the vaccine will help lessen the severity of the disease and shorten the duration of time that a person is sick, Arnold said, adding, “We recommend this.”

(The Associated Press contributed to this report.)