Is this because of my OCD or an legitimate fear?

That day in the restaurant, the waiter accidentally switched my drinks with another person. He end up fixing the mistake by switching it back.

Now, after i drank it, throughout the day, I have fears of the other person putting things in it. I have thoughts like, maybe she wanted to kill herself and put poison in it. Or maybe she needed to take some medication, and put it inside the drink. Or maybe if she drank it and her saliva is dangerous.

Am I just having another OCD problem, or is this a legitimate fear? Should I be afraid?
 
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