You will be given a definition of a task first, then some input of the task.
In this task, you are given two sentences in the English language (Sentence 1 and Sentence 2). Your task is to identify the connecting word between the two sentences.

Sentence 1:The mechanisms for infection , proliferation , and persistence of a virus in cells of the host are crucial for its survival . Sentence 2:For example , some diseases such as measles employ a strategy whereby it must spread to a series of hosts .
Output:
for example