I've only ever trusted many people in my life. It sounds odd to say 'I've only ever' at the beginning, but this is how teenagers talk. For example, when you tell them a secret they say "I won't tell anyone" however the next day everyone knows your secret. When you confront your friend they say "I didn't tell anyone except him, him, her, her, him, her, her, her, her, and they might've told their friends."
The vast majority of these people I've had to trust are doctors and nurses.
I've had no choice but to trust doctors and nurses. Not that I trust every one of them: I don't, with good reasons not to (Like the nurse who always gets my weight wrong). But when a doctor finally believes you're sick, you tend to trust this person will help you. Or if you've ever been rushed into hospital and are in so much pain you can't think for yourself, you know the feeling of putting your trust into someone's hands. Even your life.