AIDs and the bubonic plague are examples of a pandemic.
The word pandemic is from the Greek word pandemos which means pertaining to all people. The word "pan" means all and the word "demos" means people.
A Pandemic is said to be a disease outbreak of global proportions. It usually caused by the emergence of a new or novel virus among humans. It is easily transmissible and causes serious illness.
The bubonic plague, called the black death was the worst pandemic in history killing 75 million people.