No research has been able to show that a bed bug has ever spread any disease
As early as 1963, bed bugs were studied to determine if they carry any human pathogens, or disease causing organisms. Many pathogens from plague to malaria have been associated with bed bugs and found in bed bugs. However, to date, no research has been able to show that a bed bug has ever spread any disease.
A study in the Gambia in the 1990s concluded that there might be a causal link between bed bugs and the spread of hepatitis; however, that study was scrutinized and the conclusion was that there is no evidence of disease transmission.
A study of five bed bugs in western Canada implied that bed bugs can carry antibiotic resistant strains of bacteria. The researchers worked in an area where the majority of patients had those bacteria on their skin surfaces. The researchers removed bed bugs and tested the insects to see if they carry the same bacteria. They found positive results, although there are no data to show whether the bacteria came from outside of the insect or from the inside. No evidence of transmission of the disease was found at all.
In the case of mosquitoes, the female adult feeds on blood and is required to lay viable eggs. All stages of bed bugs after egg feed on blood and both male and females feed. This is a striking difference from mosquitoes. Of course, we know that mosquitoes spread disease such as malaria, dengue fever, yellow fever, and West Nile Virus, just to name a few.
The disease transmission capabilities of bed bugs are not fully researched, but there is no scientific evidence that bed bugs have transmitted any disease through the bite. Some speculate that if a bed bug crawls over an open wound and the bed bug tracks pathogens, they can infect a person. This is probably true but it is true for any insect that walks across contaminated areas and then walks onto a wound so there is no cause for additional concern regarding bed bugs.