avoid like the plague
Evade or elude at any cost, shun. For example, Since Bob was taken into police custody, his friends have been avoiding him and his family like the plague. This seemingly modern expression dates from the Latin of the early Middle Ages, when Saint Jerome (a.d. 345-420) wrote, "Avoid, as you would the plague, a clergyman who is also a man of business." The plague, a deadly infectious disease in his day, has been largely wiped out, but the term remains current.