Headache, fatigue, body aches, nausea. Those symptoms commonly accompany the flu, but could indicate something more dangerous carbon monoxide poisoning a danger more real in the wintertime with heaters working overtime and doors and windows sealed to keep out the cold.
The difference between carbon monoxide poisoning and the flu? Only a detector or blood test can tell.
"One of the problems with carbon monoxide poisoning is that the symptoms can be nonspecific," said Dr. Alvin C. Bronstein, medical director at the Rocky Mountain Poison Center in Denver. "It is odorless and tasteless, so there is no way to know it is in the house."
The initial symptoms of carbon monoxide poisoning mimic those of the flu tiredness, headache, upset stomach and body aches. During prolonged exposure, carbon monoxide levels in the body gradually increase, and can become life-threatening. Some signs of severe poisoning are chest pain, irregular heartbeat, seizures and coma.
"It tends to sneak up on people," Bronstein said.
Every winter the Moffat County Sheriff's Department receives reports of carbon monoxide poisoning. Most cases can be traced to malfunctioning natural gas and propane furnaces or cars idling in poorly-ventilated areas, such as garages, said Undersheriff Jerry Hoberg.
A Nevada woman on a hunting trip in Moffat County earlier this month suffered a severe case of carbon monoxide poisoning. She wasn't feeling well and went into a Wells Fargo cargo trailer, heated by a propane heater, to sleep while the rest of her party went into the woods. When the hunters returned approximately 12 hours later, the woman was still breathing, but her face was purplish and the hunters couldn't wake her. She remains hospitalized in Denver in critical condition.
It was the first case of carbon monoxide poisoning in a hunting camper that Hoberg could recall in some time.
"People need to make sure rooms with propane heaters are well ventilated," he said.
When people inhale carbon monoxide, it replaces oxygen in their bloodstream and causes a lack of oxygen to the organs and brain.
"It turns out the blood likes carbon monoxide more than it likes oxygen," Bronstein said. "People, in a sense, smother."
Anyone who feels sick and suspects poisoning should see a physician, Bronstein said. Doctors can check the carbon monoxide levels in the blood and treat patients with severe cases in hyperbaric oxygen chambers.
Pregnant women need to be especially careful of carbon monoxide exposure, Bronstein said. The fetus' blood holds on to carbon monoxide more tightly than a child's, keeping it in the bloodstream longer and causing more damage.
The best defenses against carbon monoxide poisoning are home detectors and knowledge of its causes.
"I think you need to be aware of it," Hoberg said. "If I had (a gas) heating system at my home, I would go out and buy a detector."