As far as I know, and I have had the delights of bed bugs on Camino - a single BB bites in a line, so one bug will leave a fairly recognisable line of feasting, one bite after another. More lines mean more bugs, and infestation. Also, bites can show immediately or after two-three days, depending upon your reaction to them. Spots of blood on a matress are a sure sign. Its always good to check the seams and folds of the matress and pillow, if you've any energy left after a good days hike. On the Salvador last year, and primitivo, I was bite-free. Happy bite-free Camino
PS but always try to do a body tick-search every day. Its those little nasty buggers you really need to be carefull of ! I always take a special tick remover with me. If you don't find ticks, but have a strange circular rash anywhere or see one on someone else, get medical attention immediately, don't hesitate.
Keith