David Kwiatkowski, a former lab technician, has been given the title "serial infector" after possibly exposing thousands of people to his hepatitis C.
He worked at different hospitals in eight states where he would steal syringes full of anesthetic, inject himself, then refill the syringe with saline and put it back on the shelf.
So he would get high and then cover his tracks, which would leave infected needles in the hospital.
Luckily this man has been caught and is now in jail, facing some serious charges.
The state Department of Health and Human Services and its Division of Public Health Services are now testing people who might have been exposed to see if they were infected.
We hope those who were infected find out soon and get the help they need.