If something happens subclinically, it happens in a way that is not easy to see or notice, especially in terms of a disease or medical condition.
When something happens subclinically, it is not easy to see or notice, so it might be hard to find or understand.
Examples:
The disease was growing subclinically.
She was subclinically affected by the illness.
The problem was getting worse subclinically.
The sickness was hiding subclinically.
The virus was spreading subclinically, so no one knew about it.
The illness was growing subclinically, like a secret in the body.