1.   Breathing higher levels of carbon monoxide causes flu like symptoms such as headaches, dizziness and weakness in healthy people.

2.   The first infection with Cocci usually causes a flu-like illness, and the patient never knows that was the cause.

3.   The flu is caused by a smaller family of viruses, which led to the development of an effective vaccine.

4.   The flu is caused by influenza types A, B and C, with A and B being responsible for the potential epidemics of infection.

5.   The vaccine is produced after health researchers decide which of the influenza viruses are most likely to cause the flu that year.

6.   A tiny change in a virus that causes flu can turn it from an unpleasant annoyance to a killer, a team of researchers has found.