Emerging infectious disease

For every decade since 1940, there has been a consistent increase in the number of EID events from wildlife-related zoonosis. Human activity is the primary driver of this increase, with loss of biodiversity a leading mechanism.^[7]


Emerging infections account for at least 12% of all human pathogens.^[8] EIDs can be caused by newly identified microbes, including novel species or strains of virus^[9] (e.g. novel coronaviruses, ebolaviruses, HIV). Some EIDs evolve from a known pathogen, as occurs with new strains of influenza. EIDs may also result from spread of an existing disease to a new population in a different geographic region, as occurs with West Nile fever outbreaks. Some known diseases can also emerge in areas undergoing ecologic transformation (as in the case of Lyme disease^[10]). Others can experience a resurgence as a re-emerging infectious disease, like tuberculosis^[11] (following drug resistance) or measles.^[12] Nosocomial (hospital-acquired) infections, such as methicillin-resistant Staphylococcus aureus are emerging in hospitals, and are extremely problematic in that they are resistant to many antibiotics.^[13] Of growing concern are adverse synergistic interactions between emerging diseases and other infectious and non-infectious conditions leading to the development of novel syndemics.


Many EID are zoonotic,^[4] deriving from pathogens present in animals, with only occasional cross-species transmission into human populations.^[14] For instance, most emergent viruses are zoonotic^[4] (whereas other novel viruses may have been circulating in the species without being recognized, as occurred with hepatitis C^[15]).

One way to classify emerging infections diseases is by time and how humans were involved in the emergence:^[32]

The 1992 IOM report^[26] distinguished 6 factors contributing to emergence of new diseases (Microbial adaptation and change; Economic development and land use; Human demographics and behavior; International travel and commerce; Technology and industry; Breakdown of public health measures) which were extended to 13 factors in the 2003 report^[28] (Chapter 3 of the report detailing each of them)


Their classification serves as a basis for many others. The following table gives examples for different factors:

Emerging Infectious Diseases between Humans and Animals[edit]

Emerging infectious diseases between human, animal have become a significant concern in recent years, playing a crucial role in the occurrence and spread of diseases.^[41][42] Human population growth, increased proximity to wildlife, and climate change have created favorable conditions for the transmission of zoonotic diseases, leading to outbreaks such as Zika, Ebola, and COVID-19. The One Health approach, which integrates animal, human, and environmental health, has emerged as a crucial tool for monitoring and mitigating the spread of infectious diseases.^[43]


Zoonotic diseases, originating from animal sources, pose a significant threat to human health. Up to 75% of emerging infectious diseases are zoonotic, originating from viruses and other pathogens that are transmitted from animals to humans. Understanding the mechanisms of transmission, the role of wildlife trade, and the importance of surveillance and early detection is crucial for mitigating the impact of zoonotic diseases on human health. Surveillance efforts involving wastewater have been identified as valuable tools for detecting early warning signs of disease emergence and providing timely interventions.^[41][42]