英语翻译

题目

英语翻译
An estimated one-third of all people are infected with tuberculosis.But the body's natural defenses are usually strong enough to prevent an active case.Even so,the bacteria remain in the body.
中的”But the body's natural defenses are usually strong enough to prevent an active case”
我理解的翻译是”但是人体天生的防护通常能足够防止．．．”an active case不知道怎么译比较好．．

答案

估计有三分之一的人感染了肺结核病毒.但是人体天生防护足够强大,通常可以遏制病毒的发作.但即便如此,细菌仍留在体内.