Hepatitis C
Peoples are at risk for getting Hepatitis C if they get blood transfusions (where a person is given blood from another person), blood products (which have blood or parts of blood in them), or organ transplants (where a person who needs a new organ is given an organ from another person), if these things have not been screened (or tested) for the Hepatitis C virus. In the United States, there has been universal screening - meaning that all blood and organs are tested before being given to another person - since 1992. Before then, about one out of every 200 units of blood carried the Hepatitis C virus; since 1992, only one in 10,000 to 10,000,000 units of blood carry the virus. The reason that there is still a low risk, instead of no risk at all, is that a person's blood does not test positive for the Hepatitis C virus until about 11–70 days after they get the disease. So every once in a while, the screening tests may not pick up on a person's infection if the person got Hepatitis C less than 11–70 days before giving blood. While Hepatitis C screening works very well, some countries still do not screen blood and organ donations for the disease because of the cost.