Have you ever watched the movie "
and the band played on"?
When HIV was first making its presence known, researchers noticed a lot of people with this new disease also had hepatitis.
Researchers suggested that blood centers start screening for hepatitis, the answer was "do you know how much that will cost?".
They did not have a test for HIV, but they did have a hepatitis test. If the blood centers tested for hepatitis, they could have prevented a lot of HIV infections. But the screening was cost prohibitive. It would have cost too much money to screen and dispose of the infected blood.
Also, the first HIV antibodies do not appear until at least 6 months after infection.
There is at least a 6 month window that a person can be infected and test negative.