 [ Symptoms ] i had black diarrhea last p m now tarry light headed and short of breath when standing d face gets pale  i did take ibuprofen occasionally for knee pain past couple weeks i ate several choc cookie night before and choc donuts next day a stomach bug has gone through my family [ Disease ] maybe many flu strains are genetically close so past infections past flu vaccines and even this year is strain may still offer some protection this year is flu vaccine is considered to be a good match not true in all previous years vaccine so there has been very good protection against the true lab confirmed cases of influenza