Why change toothbrushes so regularly?

The vast majority of “normal colds” are caused by viruses, not bacteria.

The huge majority of colds are caused by rhinoviruses, not bacteria.

Also, while it’s true that a lot of people don’t understand the difference between a cold and the flu, the symptoms of the flu are usually so severe that no one who has the disease would call it a cold. The symptoms of the flu are a cough, high fever, sore muscles and weakness, all with sudden onset. The flu usually doesn’t cause a stuffy nose or sneezing. Someone with a cold is usually able to function normally, while someone with the flu often can’t function at all for a few days.

Again, I challenge you to provide a citation.

I can only say that this response speaks for itself.