疾病的英文可数吗

例句：

The test is used to diagnose a variety of diseases.

此项化验可用于诊断多种疾病。

Infectious diseases can be acquired in several ways.

传染病的感染途径有几种。

It took years to understand many perplexing diseases.

许多疑难病症要耗时多年才能搞明白。

The biology of these diseases is terribly complicated.

这些疾病的作用方式极其复杂。

The public is generally uninformed about these diseases.

大众对这些疾病普遍知之甚少。