A linear series of lesions looks like... bed bugs. There aren't many linear aspects to the human body. A line of marks might follow a dermatome, as in shingles (where the virus breaks out in a pattern following the nerves it lives in), but other than that there aren't many differentials.
Of course, you have to know the history. On Friday morning, my back itched. On Friday, I was on public transportation, and on Friday and Saturday night, I spent the night in a foreign bed. It was on Saturday morning that I saw the above in the bathroom mirror and had someone take a photo.
My normal pattern is to go from work to home to gym to grocery store to restaurant, and that's about it. It's been months since a stranger has spent the night in my bed or I in another bed. And I don't have pets. This isn't the history of someone likely to have picked up an infestation.
What are the possibilities? (1) I picked up bed bugs in the ICU. (2) I picked up bed bugs on public transportation on Friday. (3) I picked up bed bugs in the foreign bed, and the itching Friday was a coincidence.
I ended up going to employee health and the infection control office. There hasn't been an outbreak in the ICU. In the end, the diagnosis was a shrug of the shoulders, based on the appearance of the lesions. They don't in fact look like bites. It's possible that I scratched my itch on Friday and had a reaction including an outbreak. Or perhaps it was something else. The solution: go home and see if more marks appear.