No one goes through life without getting ill.沒有人一生從不生病的。
We usually think of illness as a bad thing.我們總認爲生病是件壞事。
Sometimes, though, it is necessary to be ill, especially when we are young.有時，生病是必須的，特別是小時候。
Thatrsquo;s because we need to build up immunity against disease and sickness.那是因爲我們必須建立起抵禦病毒和疾病的免疫力。
Most children will get measles and mumps etc. when they are quite young.大多數孩子小的時候會出疹子，得腮腺炎。
Then the effect of these illnesses is not usually very bad.這些病的'後果並非不好。
If we get them when we are older, it can be much worse for us.如果大一點的時候才得這些病，對我們更不好。
Throughout history, we have fought against diseases and illnesses and many will have been eradicated from most countries by the end of this century.有史以來，我們已經同疾病做了許多鬥爭，許多疾病也將在本世紀末在許多國家完全被消除了。
But new ones seem to come along to challenge us, or perhaps these new ones were always there but we did not identify them.但是似乎又有新的疾病襲來，向人們提出挑戰。也許，這些新的疾病一直都存在，只是我們沒有發現。