Infectious disease outbreaks result in mortality or morbidity of many humans and wild and domestic animals and plants. Many a time that leads to large-scale economic and socio-cultural losses. However, exposure to pathogens does not always lead to infections or the spread of diseases since diverse factors are involved in the manifestation of diseases. The infectious organisms that cause diseases and the host are a part of the multidimensional biodiversity and a quintessential part of the ecological web. Hence, a manifestation of an infectious disease is through a chain of events that favor high contact of the pathogenic species with the host species, directly or indirectly, or through intermediate hosts/vectors. This context makes it important to recognize that preservation of natural habitats possibly has a direct bearing on public health since habitats with high biological diversity have the potential for checks and balances of population growth and could curtail disease transmission and the manifestation of diseases in many a case. Besides, diverse and heterogeneous (and largely anthropogenic) issues such as rapid urbanization, sprawling inroads into natural habitats, increasing human-animal conflicts, decreasing environmental quality, languid waste disposal systems, rising contamination/pollution of the natural systems, increasingly unwholesome lifestyle, etc. makes the condition much more complex. This book addresses human diseases from a wider and holistic perspective, especially looking at morbidity from an ecological viewpoint. It also looks at infections from an evolutionary perspective. These perspectives, although known, are largely neglected in healthcare systems in vogue. Such a perspective would be an eye-opener for the healthcare providers, and the public at the receiving end of the increasingly expensive healthcare services.