Lyme disease is now the most common arthropod-borne illness in the U.S.
Insects are capable of spreading many diseases, but very few are actually caused by the insects themselves. Instead, other organisms are passed through saliva when a person is bitten. These tiny organisms can range from bacteria to viruses to protozoa. Unfortunately, their presence in insects is one reason why people have become so acutely aware of pests such as mosquitoes, ticks, and fleas, as well as the diseases that may be contracted through their bites.