Why are many Diptera considered potentially dangerous to humans?

Many Diptera are carriers of various infections and diseases. For example, a mosquito, although it cannot get certain diseases that are very dangerous for humans, can transmit them from animals to humans or from one person to another. This happens because when a mosquito sucks blood from a sick person, a certain amount of contaminated blood will remain in its proboscis, and when it begins to feed on the blood of a healthy person through the skin from the mosquito’s proboscis, an infection or a virus enters the human body.