Josephine must have had the disease very mildly as she showed no symptoms.

约瑟芬那时一定病得很轻，因为她没表现出什么症状。

《柯林斯英汉双解大词典》

You may get no symptoms at all, or only mild ones.

你可以完全没有症状，或是只有轻微症状。

youdao

Shocked! The problem for me was that there were no symptoms; it seemed to have sneaked up on me.

震惊了！我的问题在于没有任何征兆；它似乎是悄悄缠上我的。

youdao

Colon cancer is one of the world's deadliest diseases, but it often has no symptoms in the early stages.

VOA: standard.2010.04.07

Here in Juarez, people with flu-like symptoms have formed long lines outside of some clinics and hospitals, even though there have been no confirmed cases of swine flu here.

VOA: standard.2009.04.30

In both cases, they may be infecting hundreds of people who have no symptoms.

WSJ: Virus's Toll in Saudi Arabia Raises Fears of Faster Spread

Most people become infected with it at some point in their lives, often with no symptoms.

FORBES: Multiple Sclerosis May Be Caused By A Virus

Two people in close contact with her were quarantined for observation but have shown no symptoms so far.

BBC: China bird flu: Beijing reports its first case