A pandemic is an epidemic of an infectious disease that has a sudden increase in cases and spreads across a large region, for instance multiple continents or worldwide, affecting a substantial number of individuals. Widespread endemic diseases with a stable number of infected individuals such as recurrences of seasonal influenza are generally excluded as they occur simultaneously in large regions of the globe rather than being spread worldwide.
A zoonosis or zoonotic disease is an infectious disease of humans caused by a pathogen that can jump from a non-human to a human and vice versa.
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection.
An epidemic is the rapid spread of disease to a large number of hosts in a given population within a short period of time. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic.
Optimal virulence is a concept relating to the ecology of hosts and parasites. One definition of virulence is the host's parasite-induced loss of fitness. The parasite's fitness is determined by its success in transmitting offspring to other hosts. For about 100 years, the consensus was that virulence decreased and parasitic relationships evolved toward symbiosis. This was even called the law of declining virulence despite being a hypothesis, not even a theory. It has been challenged since the 1980s and has been disproved.
An emerging infectious disease (EID) is an infectious disease whose incidence has increased recently, and could increase in the near future. The minority that are capable of developing efficient transmission between humans can become major public and global concerns as potential causes of epidemics or pandemics. Their many impacts can be economic and societal, as well as clinical. EIDs have been increasing steadily since at least 1940.
Avian malaria is a parasitic disease of birds, caused by parasite species belonging to the genera Plasmodium and Hemoproteus. The disease is transmitted by a dipteran vector including mosquitoes in the case of Plasmodium parasites and biting midges for Hemoproteus. The range of symptoms and effects of the parasite on its bird hosts is very wide, from asymptomatic cases to drastic population declines due to the disease, as is the case of the Hawaiian honeycreepers. The diversity of parasites is large, as it is estimated that there are approximately as many parasites as there are species of hosts. As research on human malaria parasites became difficult, Dr. Ross studied avian malaria parasites. Co-speciation and host switching events have contributed to the broad range of hosts that these parasites can infect, causing avian malaria to be a widespread global disease, found everywhere except Antarctica.
A reverse zoonosis, also known as a zooanthroponosis or anthroponosis, is a pathogen reservoired in humans that is capable of being transmitted to non-human animals.
Novel coronavirus (nCoV) is a provisional name given to coronaviruses of medical significance before a permanent name is decided upon. Although coronaviruses are endemic in humans and infections normally mild, such as the common cold, cross-species transmission has produced some unusually virulent strains which can cause viral pneumonia and in serious cases even acute respiratory distress syndrome and death.
Human coronavirus OC43 (HCoV-OC43) is a member of the species Betacoronavirus 1, which infects humans and cattle. The infecting coronavirus is an enveloped, positive-sense, single-stranded RNA virus that enters its host cell by binding to the N-acetyl-9-O-acetylneuraminic acid receptor. OC43 is one of seven coronaviruses known to infect humans. It is one of the viruses responsible for the common cold and may have been responsible for the 1889–1890 pandemic. It has, like other coronaviruses from genus Betacoronavirus, subgenus Embecovirus, an additional shorter spike protein called hemagglutinin-esterase (HE).
Spillover infection, also known as pathogen spillover and spillover event, occurs when a reservoir population with a high pathogen prevalence comes into contact with a novel host population. The pathogen is transmitted from the reservoir population and may or may not be transmitted within the host population. Due to climate change and land use expansion, the risk of viral spillover is predicted to significantly increase.
In parasitology and epidemiology, a host switch is an evolutionary change of the host specificity of a parasite or pathogen. For example, the human immunodeficiency virus used to infect and circulate in non-human primates in West-central Africa, but switched to humans in the early 20th century.
Colin A. Chapman is a professor at the Vancouver Island University in British Columbia, Canada. In addition, he is a Fellow of the Royal Society of Canada, an Honorary Lecturer at Makerere University in Uganda, a Member of the Committee of Research and Exploration at National Geographic, and an Associate Scientists of the Wildlife Conservation Society in New York. Prior to taking on his position at McGill University, he was at the University of Florida in the Department of Zoology from 1993 to 2004. He is internationally recognized for his 30+ years of research into primate ecology, population regulation, nutrition, and disease dynamics and for his contribution to conservation globally.
Groups of animals and humans that live in places with high population density have an increased risk of disease prevalence. In looking at sociality and disease transmission, an examination of how social grouping strategies may reduce or increase the spread of disease is critical for the health of large groups of people. Social groups, community structures, and cultures affect the use of different strategies and behaviors to reduce the spread of disease.
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 are increasing at unprecedented rates which can have lasting impacts on public health, ecosystem health, and biodiversity.
Wildlife trafficking practices have resulted in the emergence of zoonotic diseases. Exotic wildlife trafficking is a multi-billion dollar industry that involves the removal and shipment of mammals, reptiles, amphibians, invertebrates, and fish all over the world. Traded wild animals are used for bushmeat consumption, unconventional exotic pets, animal skin clothing accessories, home trophy decorations, privately owned zoos, and for traditional medicine practices. Dating back centuries, people from Africa, Asia, Latin America, the Middle East, and Europe have used animal bones, horns, or organs for their believed healing effects on the human body. Wild tigers, rhinos, elephants, pangolins, and certain reptile species are acquired through legal and illegal trade operations in order to continue these historic cultural healing practices. Within the last decade nearly 975 different wild animal taxa groups have been legally and illegally exported out of Africa and imported into areas like China, Japan, Indonesia, the United States, Russia, Europe, and South America.
Pandemic prevention is the organization and management of preventive measures against pandemics. Those include measures to reduce causes of new infectious diseases and measures to prevent outbreaks and epidemics from becoming pandemics.
Peter Daszak is a British zoologist, consultant and public expert on disease ecology, in particular on zoonosis. He is the president of EcoHealth Alliance, a nonprofit non-governmental organization that supports various programs on global health and pandemic prevention. He is also a member of the Center for Infection and Immunity at the Columbia University Mailman School of Public Health. He lives in Suffern, New York.
Marc Lipsitch is an American epidemiologist and Professor in the Department of Epidemiology at the Harvard T.H. Chan School of Public Health, where he is the Director of the Center for Communicable Disease Dynamics. He has worked on modeling the transmission of Coronavirus disease 2019 (COVID-19).
David Hayman is a New Zealand-based epizootic epidemiologist and disease ecologist whose general multi-disciplinary work focuses on the maintenance of infectious diseases within their hosts and the process of emergence and transmission to humans specifically related to bats. He has gathered data on the relationship between ecological degradation due to anthropogenic actions, and increased pathogen emergence in humans and animals. During COVID-19 he was involved as an expert in several international collaborations, some convened by the World Health Organization, and was a regular commentator in the New Zealand media about the country's response to the pandemic. He has had lead roles in research organisations at Massey University and Te Pūnaha Matatini and was the recipient of the 2017 Rutherford Discovery Fellowship Award. Since 2014 Hayman has been a professor at Massey University.
