West Nile Virus

[McClef]

Blood is tested for various problems before it is used but they cannot run checks for absolutely every possibility, hence the tendency to err on the side of caution.

I cannot give blood anyway because I am diabetic.

[wvpiper]

I cannot give blood anyway because I am diabetic.

According to the Red Cross, you can IF your diabetes is controlled.
List of guidelines, here, including discussion of Mad Cow.
http://www.redcross.org/en/eligibility