Page "Apollo" Paragraph 36

In the Iliad, Apollo is the healer under the gods, but he is also the bringer of disease and death with his arrows, similar to the function of the terrible Vedic god of disease Rudra.

He sends a terrible plague ( λοιμός ) to the Achaeans.

The god who sends a disease can also prevent from it, therefore when it stops they make a purifying ceremony and offer him an " hecatomb " to ward off evil.

When the oath of his priest appeases, they pray and with a song they call their own god, the beautiful Paean.