Various warnings are now being issued that while headaches, nausea and fatigue are more often taken to be symptoms of H1N1, these could very well be those of poising by carbon monoxide, a colorless, odorless gas, and doctors can often get confused while diagnosing these, especially on the back of the rapidly rising number of Swine Flu cases.

"The symptoms are so similar. It can look just like the flu", said Carson Harris, an emergency room physician at Regions Hospital in Minnesota.

When the case is of poising by carbon monoxide, people often wake up with blurred vision and disorientation, in addition to shortness of breath and bouts of vomiting. The symptoms would, however, soon disappear as soon as these people are away from the affected area, and are breathing in fresh air again.

During the winter months, the chances of getting affect by carbon monoxide increase, because these are the months when the gas can be released by gas furnaces which are not working well, wood burning stoves, fireplaces and propane heaters.

Fire officials are now urging residents to install "carbon monoxide detectors" and visit a doctor as soon as any of these symptoms occur.