Short answers, pulled from the story.
An infection is simply the entry of pathogenic agents into tissues, their multiplication, and the host's reaction to these invaders and the toxins they produce. These agents range from bacteria like Staphylococcus aureus to viruses such as HIV and Rhinovirus.
The Great Plague of Marseille in 1720 killed 100,000 people in the city and surrounding provinces within months. Historical records show that this event was one of several major pandemics shaping human demographics throughout history.
Mary Mallon known as Typhoid Mary was an asymptomatic carrier who infected 53 people during her career as a cook. Three of those individuals died from the infection she transmitted while working without showing symptoms herself.
Historical records show that the Black Death of 1347 to 1352 reduced Europe's population by approximately 100 million over five years. This massive demographic shift occurred between the 14th century start date and the end of the pandemic period.
Antibiotics only work for bacteria and do not affect viruses such as HIV or Rhinovirus. Common classes include penicillin cephalosporins aminoglycosides macrolides quinolones and tetracyclines which target specific bacterial pathogens.