There is no evidence to prove that bedbug bites cause infections or disease themselves. It is suspected that they aid in the spread of infectious diseases, but this has not been proven. At worst a person scratching the bites makes himself more susceptible to infection by aggravating the wound sites and potentially introducing bacteria.
The Centers for Disease Control, or CDC, and the Oxford Medical Journal are divided on the issue of bedbugs spreading disease. It is the CDC's firm belief that bedbugs in no way spread infectious diseases. While the Oxford Medical Journal believes that the bugs spread diseases, it has not been proven yet. However, the journal has found 40 different infectious agents it believes to be spread directly by bedbugs.
Doctors believe that the only way a person suffers infection as a result of bedbug bites is from scratching the bites and introducing infectious agents. Studies on bedbugs are ongoing, so if the bugs do spread diseases it should become apparent soon. Bedbugs bites create itchy lesions on the skin that scratching causes to break open. The dirt and bacteria underneath a person's nails can get into these open wounds and cause illness.