With respect to bites, no one breed causes most of them.[3] A 2015 literature review concluded that "breed is a poor sole predictor of dog bites".[9] In the United States pit bull-type are the most frequently identified breeds in cases of severe bites with Rottweiler dogs also being common.[3][9] This is partly attributed to their size and the fact that they are more frequently owned by people involved in crime.[9]
When dogs are near humans with whom they are familiar, they normally become less aggressive. However, it should not be assumed that because a dog has been with humans, it will not attack anybody – even a family member. Caution needs to be taken when approaching new dogs for the first time.[10]
A study based on recent data from 2000–2009, published in 2013, compared media accounts with reports available from animal control officials, determined that, of their sample of 256 dog bite related fatalities, breed could only be validly determined in 45 cases, and the attacks in these 45 cases were dispersed among 20 different breeds and 2 known mixes. For a further set of 401 dogs in media accounts of dog bite related fatality, reported breed differed between different media accounts of the same attack 31% of the time, factoring in animal control accounts produced disagreement on breed for 40% of attacks.[11]
A 2000 study by the US by the Centers for Disease Control and Prevention (CDC) reports of 327 people killed by dogs "pit bull terrier" or mixes thereof were reportedly involved in 76 cases. The breed with the next-highest number of attributed fatalities was the Rottweiler and mixes thereof, with 44 fatalities.[2]