Took antibiotics for a viral infection, never had sex, but my period is a week late?

Late period: Reasons for missed/late periods: low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, ^ stress, illness, eating disorders (bulimia or anorexia), anovulatory cycle (no egg released), travel, hormone irregularities, drug use, meds (i.e., birth control) or medical problems. #1 reason is pregnancy. By the way - antibiotics usually aren't indicated for.

Delayed mens: One week delay is nothing to be concerned about. Illness can throw off the timing.