The time to start thinking about the flu is before a widespread outbreak of the disease occurs, according to the federal Centers for Disease Control. Flu season extends from October to May and typically peaks in mid January.

Flu shots are the best way to avoid developing influenza, which kills between 20,000 and 40,000 Americans each year and infects up to 10 to 20 percent of the population, CDC officials say. The virus causes fever, sore throats, muscle aches, coughs and fatigue.

The vaccine, which is good for one year, protects people from three strains of the flu. This year, the prevalent strains are A Taiwan, A Shanghai and B Yamagata.

The cost of the vaccine ranges from $8 to $15. Some public health clinics provide free shots.

CDC officials strongly recommend annual flu shots for:

Those over age 65.

Nursing home residents.

People with heart, lung or kidney problems.

Anyone with diabetes or other chronic illnesses including AIDS.

Doctors, nurses, health care workers and employees in nursing homes or other long-term care facilities.

Home care providers and family members of people who are chronically ill.

Source: Centers for Disease Control