The number of flu deaths and cases skyrocketed last week in San Diego County, doubling the season-to-date count of residents sickened or killed by the contagious virus for a total that dwarfs the number reported at this time last year. County public health officials reported Wednesday that 11 deaths have been attributed to the virus as of last week, up from five the week before. At this time last year, four deaths had been attributed to the flu, officials said.