Flu isn’t new. More than 2,000 years ago (412 B.C.E.), the Greek physician Hippocrates, known as the father of modern medicine, described a respiratory illness we now know as influenza, or flu. He was describing “the cough of Perinthus” in a text known as Epidemics. By the 1170s, outbreaks of influenza-like illnesses began appearing in historical accounts. The keeping of pigs and poultry may have fueled the outbreaks, as the continually mutating influenza virus jumped to humans after circulating among these domestic animals.