While the symptoms of headache, nausea and fatigue are usually associated with the flu, they’re also a warning sign of another serious health problem – carbon monoxide poisoning. With the flu season starting, Alliant Energy is encouraging customers to recognize the signs of carbon monoxide poisoning and take precautions.  Alliant Energy says fall is the peak time for carbon monoxide problems as homeowners are turning on their furnaces for the first time and their homes are sealed up tight.  If flu symptoms are not accompanied by fever, if everyone in the family is ill, or if the symptoms disappear when you leave the house, it could be carbon monoxide poisoning.  They say if you suspect carbon monoxide is in your home, get everyone out of the house and call a service professional to inspect your appliances right away.  They also suggest installing a quality carbon monoxide detector in the home.