It is obvious that with the increasing size and density of human populations, the transmission of infectious diseases will increase. As illustrated by the image, such increases are occurring at a faster rate in areas that are developing or have more tropical climates.
However, population growth alone is not the major driver but rather the activities of these increased numbers that have the more profound impact. Also, the mobility of humans leads to increased disease transmission; global air travel is a big factor here. Many other activities of larger populations such as their food preferences, urbanization, companion animals, agriculture, and many, many others all play a role.
