I think it comes down to hygeine really. I had a sv* when I was 8 and not again until I was 24 (and that may have been fp* because nobody else got sick). I didn't have another sv* until last year at 28. The one I had when I was 8, was yucky, 12 hours straight of v* every 30 minutes or so. I don't remember having d*. Then when I was 24 I was 36 weeks pregnant with my youngest son, my hubby made me shrimp curry for my birthday, that night about 3 am I was up v* and d* for about 5 hours straight. It was awful! Nobody else got sick, just me. Then when I was 28 (last year) same scenario as now, my oldest son, my younger son, my hubby and I. All within 2 days apart (hubby and I together though) and it was very mild.