Disease ecology is a sub-discipline of ecology concerned with the mechanisms, patterns, and effects of host-pathogen interactions, particularly those of infectious diseases. For example, it examines how parasites spread through and influence wildlife populations and communities. By studying the flow of diseases within the natural environment, scientists seek to better understand how changes within our environment can shape how pathogens, and other diseases, travel. Therefore, diseases ecology seeks to understand the links between ecological interactions and disease evolution. New emerging and re-emerging infectious diseases (infecting both wildlife and humans) are increasing at unprecedented rates which can have lasting impacts on public health, ecosystem health, and biodiversity.

Parasitic infections, along with certain transmitted diseases, are present in wildlife which can have severe health effects on particular individuals and populations. Constant host-parasite interactions make disease ecology critical in conservation ecology.

Ecological factors that can determine the persistence and the spread of diseases are population size, density, and composition. Host population size is important in the context of host-parasite interactions since the spread of diseases needs a host population large enough to sustain parasitic interactions. The health of the overall population (and the size of the weakened population members) will also influence the way that parasites and diseases will transmit among members. Additionally, competition and predation dynamics in the ecosystem can influence the density of potential hosts which can either propagate or limit the spread of diseases.

In some cases when a parasite has weakened an animal it will become easier prey for a predator species. Occasionally predators will prefer feeding on the sick or infected prey even though they carry a parasite because of the opportunity weak prey present. Without the presence of a predator species the prey species would likely exceed manageable numbers therefore leading to the rapid spread of pathogens throughout the prey population. Available host numbers increased when the infected individuals are not removed due to low predation. However, there are some situations where predator feeding can disturb a pathogen that previously was dormant leading to an epidemic that otherwise would not have occurred. Some parasites are able to survive when their host species is consumed leading to the parasite being distributed in the waste of the predator which can continue the spread of disease.

Parasitism in disease ecology is important because it can shape the way many habitats function because they are disease carriers. These diseases can alter the timing of events, biogeochemical cycles, and even the flow of energy in a habitat. Parasites are able to limit population growth and reproduction of species which may lead to a shift in the balance of an ecosystem. Other ways parasites impact systems are through nutrient cycles. Parasites are able to create imbalances of the elements in a system through the relationship they have with a host and the host's diet.

Biological factors that can determine the persistence of diseases include parameters pertaining at the level of the individual within the population (one single organism). Sex differences are found to be prevalent in disease transmission. For example, male American minks are larger and travel wider distances, making them more prone to come into contact with parasites and diseases. The host species age may additionally affect the rate in which diseases are transmitted. Younger members of populations have yet to acquire herd immunity and are therefore more susceptible to parasitic infections.

Anthropogenic factors of disease spread can be through the introduction or translocation of wildlife for conservation purposes by humans. Additionally, human activity is changing the way in which diseases move through the natural environment.

Humans are strongly impacting how diseases spread by creating what is known as "novel species associations". Globalization, mainly through world travel and trade, has created a system in which pathogens, and other species, are more in contact with one another than before. Ecological disruption, including habitat fragmentation and road construction, degrade natural landscapes and have been studied as drivers of recent emergence and re-emergence of infectious diseases worldwide. Scientists have speculated that habitat destruction and biodiversity loss are some of the main reasons influencing the rapid spread of non-human, disease carrying vectors. The loss of predators, that mitigate the ability for pathogen transmission, can increase the rate of disease transmission. Human anthropogenic induced climate change is becoming problematic, as parasites and their associated diseases, can move to higher latitudes with increasing global temperatures. New diseases can therefore infect populations that were previously never in contact with certain pathogens.