Wilton contact tracers have determined the number of positive cases connected to a weekend gathering of high schoolers earlier this month stands at 25.   First Selectman Lynne Vanderslice says without swift containment, cooperation and contact tracing, the cases easily could have been double that or more.  With both the school outbreak and one at a home fore retired nuns, Vanderslice noted that the town saw the fast speed at which coronavirus can spread.  Previous gatherings and the one earlier case at The School Sisters of Notre Dame didn't spread as quickly and Vanderslice says they don't have answers for why these two new situations were different.