[RickM]

Influenza is the flu.

As Moses states, pneumonia is commonly brought on...this happened to the first gentleman. The second suffered brain swelling. Apparently it's unlike swelling that results from trauma. With the trauma based swelling pressure can be relieved, with the type this second man had it could not.

Something I heard recently, all influenza strains that affect humans are from birds.

Denis, The flu shot formula changes often, perhaps every year. Scientists take an educated guess as to which strain will be of particular threat that season and vaccines are developed as a result. So, if they're off he mark the vaccination may not work as hoped.