Ko2 (IMAGE) Duke University Caption This digitally-colorized scanning electron microscopic (SEM) image shows Salmonella bacteria (red) invading an immune cell (yellow). Salmonella Typhi is the cause of typhoid fever. Researchers at Duke have discovered human genetic variation can impact both invasion of Salmonella into cells and typhoid fever risk in people. Credit CDC Public Health Image Library (NIAID) Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.