Thousands sickened in early, severe flu season
Especially virulent strain of virus is cropping up
Ryan Nishimoto, 11, gets flu shot in Arvada, Colorado.
Americans should be prepared for what health experts are saying is an already-bad flu season.
Tiredness (can be extreme)
Drink plenty of liquids
Avoid using alcohol and tobacco
Take medication to relieve the symptoms
(CNN) -- Thousands of people have been sickened across the country with what health officials say is a severe strain of influenza in a season that started earlier than expected.
Colorado is one of the hardest-hit states. Four children there have died from the highly contagious respiratory virus.
"One of the reported deaths from flu this year was of a child with symptoms that were not consistent with the flu," said Dr. Ned Calonge, Colorado's chief medical officer.
"The loss of this child is tragic, but parents need to know this is a very unusual case, and that there have not been any similar cases in Colorado or Texas, where flu activity has been the worst to date in the United States this year," he said in a statement on the Colorado Department of Public Health and Environment Web site.
Colorado has widespread flu activity, the health department said, and in the first three days of this week alone, more than 1,300 cases were reported.
Each year, more than 36,000 Americans die of complications from influenza, according to the Centers for Disease Control and Prevention.
Pneumonia, bronchitis, and sinus and ear infections are three examples of complications from flu. Flu can also make conditions such as asthma or heart disease much worse, according to the CDC.
In Texas, flu activity was also reported to be widespread, meaning it was present in high numbers in more than half the state's 11 public health regions. This week marks the sixth consecutive week the state has recorded widespread flu activity.
"We're seeing a lot of influenza earlier in the season than usual," said Texas Commissioner of Health Eduardo Sanchez in a statement on the state's public health Web site.
"We're concerned that with the increased travel during the holidays, the flu situation could worsen."
One factor in the bad flu season is that an especially virulent strain of the virus is cropping up -- a strain that was not included in this year's flu vaccine, health officials said.
But people should still get the flu shot, Sanchez said, because it contains similar strains and "most likely it will offer some protection" against the other.
Because influenza is caused by a virus, antibiotics cannot cure it.
Despite continuous urging by federal, state and local health officials that people of all ages get a flu shot this year, many have not.
CDC guidelines suggest that everyone over the age of 50 get the flu vaccine. It also recommends a shot for children and adults with respiratory ailments, infants ages six to 23 months, and pregnant women who will be in their second or third trimester during flu season.
According to the CDC, only 34 percent of 50- to 64-year-old people got the vaccine, less than 36 percent of health care workers, and fewer than 10 percent of children with asthma.
Last week, Health and Human Services Secretary Tommy Thompson urged people to be vaccinated, even though the flu season has already begun.
"There is plenty of vaccine to meet demand, so protect yourself and those who you love and go out and get vaccinated right now," Thompson said in a statement on the CDC Web site.
CDC Director Dr. Julie Gerberding said it takes about two weeks for the flu vaccine to develop its protection, and she sought to dispel myths about the shot that keep some people from getting it.
Betty Miller, a public health nurse, administers a flu shot in Arkansas.
"The vaccine is safe and effective, and because the vaccine is made with killed virus it will not give you the flu," she said in a statement on the CDC Web site.
The Web site describes the symptoms of the flu as fever, headache, extreme fatigue, dry cough, sore throat, nasal congestion and body aches.
It is spread when infected people cough, sneeze or speak and send droplets into the air. It can also be spread by when a person touches a surface that has the flu virus on it and then touches her nose or mouth.
The CDC recommends people suffering from the flu drink plenty of liquids, avoid using alcohol and tobacco, and take medication to relieve the symptoms of flu.
However, the Web site warns that aspirin should not be given to children or teenagers who have flu-like symptoms -- particularly a fever -- without first speaking to a doctor.
The aspirin can cause a rare but serious illness called Reye syndrome. Children or teenagers can be given aspirin-free medications.