Low-grade exposure to carbon monoxide can result in nonspecific symptoms that may be mistaken for flu.
Flu-like symptoms in subacute carbon monoxide poisoning:
(1) headache
(2) nausea
(3) dizziness
(4) syncope
(5) malaise
Carbon monoxide poisoning tends to be more common in the winter with closed windows and the need for heating, but so is the spread of viral infections.
Factors that may suggest the diagnosis:
(1) other residents with similar symptoms (also seen with viral infections)
(2) use of a carbon-based heating system (gas, coal, oil, wood, etc)
(3) malfunctioning, alternative or older carbon-based heating system (use of a camp stove as heater)
(4) feeling better when away from and getting worse when back home
It is very unlikely that the patient will have cherry red skin color.
If the question is raised, then blood should be tested for carboxyhemoglobin. A carboxyhemoglobin level within the normal range does not exclude a low-grade exposure, while minor elevations can be seen in smokers.
