Influenza has likely been around for 1000 years, though     1     (it) cause was only identified     2     (relative) recently.

One of the     3    (early) reports of an influenza-like illness comes from Hippocrates, a well-known ancient Greek doctor     4     described a highly infectious disease from northern Greece in 410 B.C..

The word influenza, however, wasn't used to describe a disease     5     many centuries later. In 1357, people called an epidemic in Florence, Italy “influenza di freddo”， which translates to “cold influence,”     6     (refer) to the disease's possible cause.

In 1414, French chroniclers used similar terms to describe an epidemic that     7     (affect) up to 100,000 people in Paris. The term influenza became commonplace to describe the disease, at least in Britain, in the mid-1700s. At the time, it     8     (think) that the influence of the cold, along with astrological influences of stars and planets , caused the disease.

In 1892, Dr. Richard Pfeiffer isolated     9     unknown bacterium from the sputum (痰)of his sickest flu patients, and he concluded that the bacteria caused influenza. He called it Haemophilus influenzae (流感嗜血杆菌). Scientists later discovered that H. influenzae causes several     10     (type) of infections, but not influenza.

Researchers finally isolated the virus that causes flu from pigs in 1931, and from humans in 1933.