The evolution of drug resistance is facilitated by a number of factors, including increasing use of antibiotics and antimalarials; insufficient controls on drug prescribing; inadequate compliance with treatment regimens; poor dosing; lack of infection control; increasing frequency and speed of travel, which lead to the rapid spread of resistant organisms; and insufficient incentives for patients, physicians, or even governments to care about increasing resistance. It is important to distinguish between risk factors for the emergence of resistance (de novo resistance) and those for the spread of resistance (primary resistance).The molecular basis of resistance may give a clue to the likelihood of resistance emerging. If a single DNA base pair mutation leads to the development of resistance, then its selection is likely to be widespread, especially if the biological fitness cost of the mutation is low. De novo or acquired resistance results in the appearance of a resistant strain in a single patient. Subsequent transmission of such resistant strains from an infectious case to other persons leads to disease that is drug resistant from the outset, a phenomenon known as primary resistance.