Ecology of infectious diseases

Zoonotic diseases or infections (Zoonoses) are ailments that are naturally transmitted from animals to humans (or vice versa). These diseases are transmitted either by the consumption of contaminated food and water, exposure to the pathogen during preparation, processing or by direct contact with infected animals or humans. Zoonotic diseases have a significant effect on public health worldwide, showing a higher incidence rate in developing countries due to lack of control strategies, as well as the lack of education in the communities. Studies have indicated that about 75% of emerging infectious disease in humans originates from animals. Many factors like agricultural practices, human and animal demography, social, cultural, religious and lifestyle habits have led to the emergence of zoonotic infections since the 1940s. Salmonella, Escherichia coli O157: H7 and Cryptosporidium are prevalent causes of disease outbreaks in the United States. The key factors that will prevent and control zoonotic diseases are based on recognition, investigation, and collaboration. Treatment is specific to the causative agent. In the last two decades, zoonotic diseases within the United States have increased in prevalence and have become a significant cause of infectious disease to humans; hence the need for continuous awareness.

Medieval York was one of the largest and most important cities in England. The close confines of the city, the household and industrial waste, alongside the air and water pollution made this a city known for its pervasive smells, which at the time were considered to be a leading cause of disease. This paper aims to present the environmental context for disease combined with the human osteological record to reconstruct the pathoecology of medieval York. Combining archaeological and historical data, we gain insight into the interplay between medieval culture, disease, health, and the urban environment. It is clear that local authorities were concerned about urban pollution, and historical evidence demonstrates that legal measures were taken to remove or regulate some of the perceived causes of pollution. There is a demonstrable trend towards improving environmental conditions in York between the 11th and mid-16th century. However, it is likely that the extant socio-environmental conditions continued to contribute to morbidity, as evidenced by the prevalence of infection.

The continual emergence of new pathogens and the increased spread of antibiotic resistance in bacterial populations remind us that microbes are living entities that evolve at rates that impact public health interventions. Following the historical thread of the works of Pasteur and Darwin shows how reconciling clinical microbiology, ecology, and evolution can be instrumental to understanding pathology, developing new therapies, and prolonging the efficiency of existing ones.

Vibrio cholerae and V. parahaemolyticus are the two Vibrio species with a major impact on human health. Diseases caused by the both pathogens are currently involved in an expansion at global scale. In this paper, we resume the ecological aspects associated with the arrival and spreading of infections caused by V. parahaemolyticus and V. cholerae in Peru from a South American perspective. Moreover, we discuss the similarities in the emergence in Peru of cholera cases in 1991 and V. parahaemolyticus infections in 1997. These two cases were used as exceptional experiments to evaluate the relationships between the Vibrio diseases and the environment. The epidemic radiations of V. cholerae and V. parahaemolyticus constitute to clear examples supporting the oceanic dispersion of pathogenic vibrios and have enabled the identification of El Niño events as a potential mechanism for the spreading of diseases through the ocean.

We monitored 11 populations of eight species of Eleutherodactylus in Puerto Rico from 1989 through 2001. We determined relative abundance of active frogs along transects established in the Caribbean National Forest (El Yunque), Carite Forest, San Lorenzo, and in the vicinity of San Juan. Three species (Eleutherodactylus karlschmidti, E. jasperi, and E. eneidae) are presumed to be extinct and eight populations of six different species of endemic Eleutherodactylus are significantly declining at elevations above 400 m. Of the many suspected causes of amphibian declines around the world, we focused on climate change and disease. Temperature and precipitation data from 1970-2000 were analyzed to determine the general pattern of oscillations and deviations that could be correlated with amphibian declines. We examined a total of 106 tissues taken from museum specimens collected from 1961-1978 and from live frogs in 2000. We found chytrid fungi in two species collected at El Yunque as early as 1976, this is the first report of chytrid fungus in the Caribbean. Analysis of weather data indicates a significant warming trend and an association between years with extended periods of drought and the decline of amphibians in Puerto Rico. The 1970's and 1990's, which represent the periods of amphibian extirpations and declines, were significantly drier than average. We suggest a possible synergistic interaction between drought and the pathological effect of the chytrid fungus on amphibian populations.

Anaplasmosis is an emerging infectious disease caused by infection with the bacterium Anaplasma phagocytophilum. In the eastern United States, A. phagocytophilum is transmitted to hosts through the bite of the blacklegged tick, Ixodes scapularis. We determined the realized reservoir competence of 14 species of common vertebrate hosts for ticks by establishing the probability that each species transmits two important strains of A. phagocytophilum (A. phagocytophilum human-active, which causes human cases, and A. phagocytophilum variant 1, which does not) to feeding larval ticks. We also sampled questing nymphal ticks from~150 sites in a single county over 2 years and sampled over 6 years at one location. White-footed mice (Peromyscus leucopus) and Eastern chipmunks (Tamias striatus) were the most competent reservoirs for infection with the A. phagocytophilum human-active strain. Across the county, prevalence in ticks for both strains together was 8.3%; ticks were more than two times as likely to be infected with A. phagocytophilum human-active as A. phagocytophilum variant 1.

Este informe se inscribe en el amplio programa de trabajo que con el lema común de Cambio Global España 2020/50, ha puesto en marcha la Fundación General de la Universidad Complutense de Madrid, con el patrocinio de la Fundación Caja de Madrid. El objetivo del programa es impulsar un proceso continuado de información, anticipación y propuestas de acción sobre el Cambio Global en España con una visión de medio plazo, con el fin de alimentar el debate integral que se estimule y
fortalezca desde la sociedad civil. Para el desarrollo de este programa, la Fundación General de la Universidad Complutense de Madrid ha constituido el Centro Complutense de Estudios e Información Medioambiental (CCEIM) entre cuyos objetivos figura la creación de un sistema de conocimiento/divulgación compartido en red en torno al “Cambio Global en España con el horizonte 2020/50” para lo que se programa, entre otras actividades, un proceso de trabajo acumulativo con la realización cada dos o tres años de informes y convenciones sobre los campos y temas clave.
Un tema central, para muchos el más importante del cambio global, es el cambio climático. Dentro de él, su impacto en la salud humana es un aspecto de especial relevancia e interés para toda la ciudadanía. Para abordar el Programa CAMBIO CLIMÁTICO Y SALUD se constituye un grupo de trabajo entre el CCEIM y Instituto Sindical de Trabajo, Ambiente y Salud (ISTAS) que convoca, con apoyo de la Sociedad Española de Sanidad Ambiental (SESA) a un amplio conjunto de profesionales expertos en los diferentes contenidos de la relación entre el cambio climático y la salud humana, para que evalúen el actual estado del conocimiento, planteen estrategias de intervención y elaboren el presente Informe de Cambio Global como documento base y central del Programa, que se ha complementado con consultas y asesoramientos de otros expertos nacionales e internacionales, que pretende ser la base para una red estable multidisciplinar de expertos colaboradores y consultores de los ámbitos de las ciencias medioambientales y de la salud, así como de otras disciplinas que puedan tener relación con el ámbito del cambio climático y la salud.

Infectious diseases cause devastating illnesses in human society, such as Coronovirus Disease 2019 (COVID-19). The ecological study of host-pathogen interactions in their environment is basic to explain the evolution, transmission dynamics and diffusion over space and time of viral agents, role of in ecosystems, impact on host populations and the burden of infectious disease on socioeconomic system. This study endeavors to explain the ecology of COVID-19 considering wind speed in polluted environments that can affect the transmission dynamics of the novel pathogen and related diffusion of COVID-19. The statistical analysis, based on a case study of Italy, suggests that high wind speed can reduce air pollution commingled with viral agents and as a consequence reduce the numbers of infected individuals of COVID-19; in particular, results here reveal that polluted cities having low wind speed (i.e., with atmospheric stability) have a greater number of infected individuals and total deaths. This study suggests the important interaction between atmospheric pollution, atmospheric circulation and transmission dynamics of the novel Coronavirus to support appropriate environmental policy of sustainability directed to reduce concentration of pollutants in the atmosphere and as a consequence the transmission dynamics of pathogen in society, improving air quality and human health.

Global losses of biodiversity have galvanised efforts to understand how changes to communities affect ecological processes, including transmission of infectious pathogens. Here, we review recent research on diversity-disease relationships and identify future priorities. Growing evidence from experimental, observational and modelling studies indicates that biodiversity changes alter infection for a range of pathogens and through diverse mechanisms. Drawing upon lessons from the community ecology of free-living organisms, we illustrate how recent advances from biodiversity research generally can provide necessary theoretical foundations, inform experimental designs, and guide future research at the interface between infectious disease risk and changing ecological communities. Dilution effects are expected when ecological communities are nested and interactions between the pathogen and the most competent host group(s) persist or increase as biodiversity declines. To move beyond polarising debates about the generality of diversity effects and develop a predictive framework, we emphasise the need to identify how the effects of diversity vary with temporal and spatial scale, to explore how realistic patterns of community assembly affect transmission, and to use experimental studies to consider mechanisms beyond simple changes in host richness, including shifts in trophic structure, functional diversity and symbiont composition.

In the 1990s Peru experienced the first cholera epidemic after almost a century. The source of emergence was initially attributed to a cargo ship, but later there was evidence of an El Niño association. It was hypothesized that marine ecosystem changes associated with El Niño led to the propagation of V. cholerae along the coast of Peru, which in turn initiated the onset of the epidemic in 1991. Earlier studies supported this explanation by demonstrating a relationship between elevated temperatures and increased cholera incidence in Peru; however, other aspects of El Niño-Southern Oscillation (ENSO) and their potential impacts on cholera were not investigated. Therefore, this study examines the relationship between El Niño and cholera in Peru from a holistic view of the ENSO cycle. A “Climate Affairs” approach is employed as a conceptual framework to incorporate ENSO’s multidimensional nature and to generate new hypotheses about the ENSO and cholera association in Peru. The findings reveal that ENSO may have been linked to the cholera epidemic through multiple pathways, including rainfall extremes, La Niña, and social vulnerability with impacts depending on the geography of teleconnections within Peru. When the definition of an ENSO event is examined, cholera appears to have emerged either during ENSO neutral or La Niña conditions. Furthermore, the analysis herein suggests that the impact of El Ni~no arrived much later, possibly resulting in heightened transmission in the austral summer of 1992. In conclusion, a modified hypothesis with these new insights on cholera emergence and transmission in Peru is presented.

Body size (SVL) of adult Eleutherodactylus coqui frogs infected versus non-infected with Batrachochytrium dendrobatidis (Bd) were compared to determine a potential fitness cost of chytridiomycosis in persisting populations. Studies were conducted at two different elevations, in a Cloud Forest (650 m) and an Elfin Forest (850 m), in El Yunque, Puerto Rico. Results showed that Bd-infected males were significantly smaller than non-infected males in the Cloud Forest, but not in the Elfin Forest. Although infected females also tend to be smaller than non-infected ones, this effect was not significant. Bd prevalence and probability of infection by this fungus was significantly greater in the Cloud Forest than in the Elfin Forest, regardless of sex. We report on differences of environmental factors in these forest types in Puerto Rico, and discuss their implications on the growth of Bd and the vulnerability of frogs to infection by this pathogen.

With the evolution of human civilization, diseases also came. A disorder of structure or function in a human, animal, or plant, especially one that produces specific symptoms or that affects a specific location and is not simply a direct result of physical injury is disease. Humans have always suffered from some kind of malfunctioning in the normal function of systems. It has changed form over a period of time and due to the combination of various factors, it is defined differently in different geographies. Human civilization is full of stories of various diseases that were inflicted upon mankind at once in the history. So, here an attempt has been made to discuss one of most prevalent infectious disease of human history i.e. tuberculosis. Tuberculosis is termed as a disease which has severely troubled only those were or are at the lower end of social ladder i.e. poors. It is also named as ‘disease of the poor’ or ‘consumption of the poor’. Developed and developing countries are compared in order to understand the extent of discrimination that poor countries, poor people has to face be it prevalence of disease or be it inequality in treatment facility available to them. There is large inequality in prevalence, CFR and treatment facilities available for tuberculosis. The paper is an attempt to see the disparity in number of new cases of TB, deaths due to TB and treatment coverage of Tuberculosis in different world economies.

Barry R. Bloom is Harvard University Distinguished Service Professor and Joan L. and Julius H. Jacobson Professor of Public Health in the Department of Immunology and Infectious Diseases and Department of Global Health and Population in the Harvard T.H. Chan School of Public Health in Boston, where he served as Dean of the Faculty in 1998 through December 31, 2008.

As Dean, he served as Secretary Treasurer for the Association of Schools of Public Health (ASPH). Prior to that he served as chairman of the Department of Microbiology and Immunology at the Albert Einstein College of Medicine from 1978 to 1990, the year in which he became an Investigator of the Howard Hughes Medical Institute (HHMI), where he also served on the National Advisory Board. In 1978, he was a consultant to the White House on international health policy.

A leading scientist in the areas of infectious diseases, vaccines, and global health, and a former consultant to the White House, Dr. Barry Bloom continues to pursue an active interest in bench science as the principal investigator of a laboratory researching the immune response to tuberculosis, a disease that claims more than two million lives each year.

For more than 40 years, he has been extensively involved with the World Health Organization (WHO). He is currently Chair of the Technical and Research Advisory Committee to the Global Programme on Malaria at WHO and has been a member of the WHO Advisory Committee on Health Research and chaired the WHO Committees on Leprosy Research and Tuberculosis Research, and the Scientific and Technical Advisory Committee of the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases. Dr. Bloom serves on the editorial board of the Bulletin of the World Health Organization.

Dr. Bloom currently serves on the Ellison Medical Foundation Scientific Advisory Board and the Wellcome Trust Pathogens, Immunology and Population Health Strategy Committee. He is on the Scientific Advisory Board of the Earth Institute at Columbia University and the Advisory Council of the Paul G. Rogers Society for Global Health Research.

His past service includes membership on the National Advisory Council of the National Institute for Allergy and Infectious Diseases, the Scientific Advisory Board of the National Center for Infectious Diseases of the Centers for Disease Control and Prevention, and the National Advisory Board of the Fogarty International Center at the National Institutes of Health, as well as the Governing Board of the Institute of Medicine.

Dr. Bloom was the founding chair of the board of trustees for the International Vaccine Institute in South Korea, which is devoted to promoting vaccine development for children in the developing world. He has chaired the Vaccine Advisory Committee of UNAIDS, where he played a critical role in the debate surrounding the ethics of AIDS vaccine trials. He was also a member of the US AIDS Research Committee.

Dr. Barry Bloom continues to pursue research on understanding the mechanisms of protection against tuberculosis, as an investigator in a Bill and Melinda Gates Grand Challenge grant with Professor David Edwards the Harvard John A. Paulson School of Engineering and Applied Sciences, where they apply nanoparticle technology to deliver needle-free spray-drying aerosol vaccines against experimental tuberculosis, with UCLA colleagues. This vitamin D-dependent antimicrobial killing mechanism is effective against the tubercle bacillus and is found in human macrophages, and is unrelated to oxygen or nitrogen radicals. This may explain the greater susceptibility of people of African and Asian descent to tuberculosis.

Sponsored by the Mexican Society of History and Philosophy of Medicine, the focus of this paper presented at the first Mexican Congress of the History and Philosophy of Medicine in Mexico City, February 24-26, 1982, focuses on approaches for the study of past human diseases. Prominent scholars have judged this topic central for understanding medical history. After sketching their contributions, the essay cites the publication of William McNeill’s Plagues and Peoples (1976) as an apt model to broaden our vision by linking epidemics to the fate of nations and civilization and altering the evolution of human societies. Such a broader and dynamic frame allows for the construction of an adaptive “ecological” model, poised to uncover multiple and complex interactions between environment and humans. Geography, climate and periodic natural disasters play essential roles in shaping habitats, disease vectors, parasites, and pathological microorganisms. Conversely, humans shape their environment, not only by creating population densities that favor pollution and local contagion, but also facilitating spread through travel, migration, and wars. Based on such an ecological framework, authors have already developed a sequence of epidemiological transitions. In conclusion: this flexible and multidisciplinary approach embraces the study of biological, clinical, cultural, and social factors that allow further elaboration based on new discoveries, notably in the field of genetics to explain past and present disease patterns.

As a zoonosis, Plague is also an ecological entity, a complex system of ecological interactions between the pathogen, the hosts, and the spatiotemporal variations of its ecosystems. Five reservoir system models have been proposed: (i) assemblages of small mammals with different levels of susceptibility and roles in the maintenance and amplification of the cycle; (ii) species-specific chronic infection models; (ii) flea vectors as the true reservoirs; (iii) Telluric Plague, and (iv) a metapopulation arrangement for species with a discrete spatial organization, following a source-sink dynamic of extinction and recolonization with naïve potential hosts. The diversity of the community that harbors the reservoir system affects the transmission cycle by predation, competition, and dilution effect. Plague has notable environmental constraints, depending on altitude (500+ meters), warm and dry climates, and conditions for high productivity events for expansion of the transmission cycle. Hum...

MozArh  (coord.  Cirad; funded by MUSE). The main objective of the project Mozambican Areanvirus at the Rodent Human interface is to assess the circulation of arenaviruses and understand its drivers, in order to inform on the risk of spill-over to humans. This includes the identification of  the social, cultural, economic and political drivers that shape the human/rodent interface.

Anaplasmosis is an emerging infectious disease caused by infection with the bacterium Anaplasma phagocytophilum. In the eastern United States, A. phagocytophilum is transmitted to hosts through the bite of the blacklegged tick, Ixodes scapularis. We determined the realized reservoir competence of 14 species of common vertebrate hosts for ticks by establishing the probability that each species transmits two important strains of A. phagocytophilum (A. phagocytophilum human-active, which causes human cases, and A. phagocytophilum variant 1, which does not) to feeding larval ticks. We also sampled questing nymphal ticks from~150 sites in a single county over 2 years and sampled over 6 years at one location. White-footed mice (Peromyscus leucopus) and Eastern chipmunks (Tamias striatus) were the most competent reservoirs for infection with the A. phagocytophilum human-active strain. Across the county, prevalence in ticks for both strains together was 8.3%; ticks were more than two times as likely to be infected with A. phagocytophilum human-active as A. phagocytophilum variant 1.

The ecological study of host-pathogen interactions in their environment is basic to explain the evolution, transmission dynamics and diffusion over space and time of viral agents, role of in ecosystems, impact on host populations and the burden of infectious disease on socioeconomic system. This study investigates the relation between diffusion of Coronavirus Disease 2019 (COVID-19) and wind resources to provide insights on how sustainable policies for energy production can improve ecosystem, reduce environmental pollution, improve public health and prevent infectious diseases in society. Results reveal that cities in regions with high wind energy production have a lower number of infections of COVID-19, whereas polluted cities with low production of energy from sustainable resources (i.e., based on wind) have higher numbers of infections and deaths. These findings underscore the importance of environmental factors based on atmospheric instability for supporting sustainable energy production and an ecosystem that protects human health from COVID-19 and similar infectious diseases.

Infectious diseases cause devastating illnesses in human society, such as Coronovirus Disease 2019 (COVID-19). The ecological study of host-pathogen interactions in their environment is basic to explain the evolution, transmission dynamics and diffusion over space and time of viral agents, role of in ecosystems, impact on host populations and the burden of infectious disease on socioeconomic system. In this context, this study analyses the ecology of the COVID-19 using data on COVID-19 cases alongside environmental data in Italy. Italy was the first European country to experience a rapid increase in confirmed cases and deaths of the novel Coronavirus disease (COVID-19). This study explains how COVID-19 transmitted so rapidly in Northern Italy, analyzing the underlying relationships between infected people and environmental, demographic, and geographical factors that influenced its spread. In particular, this study finds out that cities with little wind, high humidity and frequently high levels of air pollutionexceeding safe levels of ozone or particulate matterhad higher numbers of COVID-19 related infected individuals and deaths. Overall, then, results here suggest that geo-environmental factors may have accelerated the spread of COVID-19 in Northern Italian cities, leading to a higher number of infected individuals and deaths.

COVID-19 brings to light the remarkable differences in the current approach to medical countermeasures given the prevalence of epidemiology in modern medicine compared to innovative methods, such as infectious ecology, that find entry into clinical research difficult, at best. While epidemiological approaches, per definition, aid in the development of clinical research methodology in public health in response to patterns of disease conditions in defined populations, this method is limited in unravelling the mystery of the unprecedented activation of hazardous pathogens triggering deadly biological response. Awareness of harmful microorganisms preceded the concept of Germ Theory, the foundation of epidemiology and immunology, by recognizing routes of transmission, including person-to-person contact, which has reemerged in hand sanitation and environmental hygiene campaigns in modern medical facilities. We provide the foundational understanding of this prominent approach and initiate a challenge to the prominence of the Pathogenic/Immunological Theories of Medicine. Through a series of papers to follow, we encourage scientists to consider alternative methods to overcoming the limitations of existing research methodologies on systemic problems. This paper provides a synopsis of the historical perspective on the spread of disease in relation to current events while laying the foundation for a collection of future research based on exploratory methods regarding the chemical activation and subsequent diffusion of microbes that elicit disease.

The fungal pathogen, Batrachochytrium dendrobatidis (Bd), causes the disease chytridiomycosis in amphibians and is responsible for the worst epizootics in vertebrate history. In some regions of the world (e.g., the Neotropics and Western United States), Bd has caused recent reductions in amphibian population abundance and species richness, while in other regions the impacts are less clear. Although Bd is present in the Midwestern United States, its history and impact in the region is not known. We used a qPCR assay to determine historic Bd prevalence in Illinois, testing 1028 specimens representing 10 anuran species, collected 1888-1989. We used two complementary sets of samples to first assess historic prevalence with the primary set, and used a secondary set to confirm Bd presence and examine older samples with a more sensitive technique. Prevalence varied among species; in the primary dataset of 1008 samples extracted with PrepMan Ultra collected 1892-1989, Bd was found in four species (11.1%, CI: 9.3-13.2%). Rana (Lithobates) sphenocephala, the southern leopard frog, had the highest prevalence (38.3%, CI 32.7-44.2%); prevalence among other infected species was <7%. Overall prevalence was <10% in most decades but >40% in the 1940s. In the secondary set of 50 samples extracted with Qiagen Blood and Tissue Kits (30 re-swabbed of the original 1008 and 20 additional older specimens), 17 of the 20 additional samples were Bd+ (85.0%, CI 64.0-94.8%) including the oldest Bd+ specimen, which was collected in 1888. We confirmed Bd presence by sequencing 42 Bd+ samples and found P99% homology with Bd sequences in Genbank. By 1900, Bd was geographically widespread throughout Illinois-40 years earlier than the current oldest estimate in the U.S.-meaning that Illinois amphibians have been coexisting with Bd for at least 126 years. This long period of coexistence from our results raises new questions about the history of Bd in North America, possible coevolution between host and pathogen, and the potential role of Bd in historic population declines.

In Peru, the climate pattern El Niño-Southern Oscillation was linked to a resurgence of cholera in 1998.  While previous studies found a temperature connection, El Niño’s impact on cholera in Peru has not been fully explored.  In this study, climate associations with cholera incidence during the 1997-98 El Niño are examined at a district-level in Piura, a coastal area located in northern Peru.  Piura is important to study because it was one of the most affected areas by cholera and El Niño in 1998.  The approach taken in this study is a “multiple pathways” perspective, which highlights various dimensions of ENSO to explain cholera linkages.  Associations were estimated at various temporal lags using bivariate regression and then mapped in ArcGIS.  The results show significant cholera associations with SST in the central equatorial Pacific and on the coast (0-1 month lag), rainfall (1 month lag), and mean and maximum temperatures (5 month lags).  Overall, the strongest consistent impact was rainfall, which supports the notion that flooding was a pathway for cholera exposure in Piura.  Local sea and air temperature associations also suggest that exposure was potentially linked to vibrio proliferation, which increased the probability of cholera risk.  Furthermore, this study shows that climate impacts on cholera were unevenly distributed across Piura, indicating that some districts were more vulnerable than others, possibly related to infrastructure deprivation.  In conclusion, the study provides a basis for future investigations, which may be useful for epidemic preparedness during future El Niños and other extreme climate events.

The study of past and present epidemics, including AIDS, must employ an ecological model to explain the relationships between bio-cultural environments and human actions. Three case studies, the 1656 plague outbreak in Rome, cholera in New York in 1831 and finally a serious epidemic of poliomyelitis or infantile paralysis in that same city in 1916 are examined within their specific temporal and cultural contexts. The examples confirm that emergency conditions prompt powerful protective sanitary responses that trump civil rights as well as buttress social divisions and prejudices. History’s role in the AIDS crisis is to restore public memory and raise questions about the meaning and consequences of disease.

Background: The seventh pandemic of Vibrio cholerae unexpectedly reached the coast of Peru in 1991, causing an explosive emergence of infections throughout the American continents. The origin and routes of dissemination are as yet unknown. A new Vibrio epidemic arose in 1997 in South America (northern Chile) when the pandemic clone of Vibrio parahaemolyticus was for the fist time detected outside of Asia. These 2 cases were concurrent with 2 episodes of El Niño.

Methods: We carried out a survey of records of V. parahaemolyticus infection and of strains existing in the Instituto Nacional de Salud of Peru between 1994 and 2005. Association between the El Niño event and the V. parahaemolyticus disease was analyzed through generalized additive models applied to time-series data with negative binomial response, selecting some oceanographic factors distinctive of the movement of the El Niño waters.

Results: Epidemiologic data and laboratory investigations of the strains showed that V. parahaemolyticus infections caused by the pandemic clone emerged in the coasts of Peru linked to the 1997 El Niño episode. The epidemic dissemination of this clone matched the expansion and dynamics of the poleward propagation and the receding of the El Niño waters. This pattern was similar to previously reported onset of cholera epidemic in 1991.

Conclusions: These findings identify the El Niño episodes as a reliable vehicle for the introduction and propagation of Vibrio pathogens in South America. The movement of oceanic waters seems to be one of the driving forces of the spread of Vibrio diseases.

Background Malaria constitutes a major cause of morbidity in the Brazilian Amazon where an estimated 6 million people are considered at high risk of transmission. Indigenous peoples in the Amazon are particularly vulnerable to potentially epidemic disease such as malaria; notwithstanding, very little is known about the epidemiology of malaria in Indian reservations of the region. The aim of this paper is to present a spatial analysis of malaria cases over a four-year time period (2003–2006) among indigenous peoples of the Brazilian State of Rondônia, southwestern Amazon, by using passive morbidity data (results from Giemsa-stained thick blood smears) gathered from the National Malaria Epidemiologic Surveillance System databank. Results A total of 4,160 cases of malaria were recorded in 14 Indian reserves in the State of Rondônia between 2003 and 2006. In six reservations no cases of malaria were reported in the period. Overall, P. vivax accounted for 76.18 of malaria cases reported ...

Zoonotic diseases or infections (Zoonoses) are ailments that are naturally transmitted from animals to humans (or vice versa). These diseases are transmitted either by the consumption of contaminated food and water, exposure to the pathogen during preparation, processing or by direct contact with infected animals or humans. Zoonotic diseases have a significant effect on public health worldwide, showing a higher incidence rate in developing countries due to lack of control strategies, as well as the lack of education in the communities. Studies have indicated that about 75% of emerging infectious disease in humans originates from animals. Many factors like agricultural practices, human and animal demography, social, cultural, religious and lifestyle habits have led to the emergence of zoonotic infections since the 1940s. Salmonella, Escherichia coli O157: H7 and Cryptosporidium are prevalent causes of disease outbreaks in the United States. The key factors that will prevent and control zoonotic diseases are based on recognition, investigation, and collaboration. Treatment is specific to the causative agent. In the last two decades, zoonotic diseases within the United States have increased in prevalence and have become a significant cause of infectious disease to humans; hence the need for continuous awareness.

Medieval York was one of the largest and most important cities in England. The close confines of the city, the household and industrial waste, alongside the air and water pollution made this a city known for its pervasive smells, which at the time were considered to be a leading cause of disease. This paper aims to present the environmental context for disease combined with the human osteological record to reconstruct the pathoecology of medieval York. Combining archaeological and historical data, we gain insight into the interplay between medieval culture, disease, health, and the urban environment. It is clear that local authorities were concerned about urban pollution, and historical evidence demonstrates that legal measures were taken to remove or regulate some of the perceived causes of pollution. There is a demonstrable trend towards improving environmental conditions in York between the 11 th and mid-16 th century. However, it is likely that the extant socioenvironmental conditions continued to contribute to morbidity, as evidenced by the prevalence of infection.

Antibody to Ebola virus was found in 14 (1.2%) of 1147 human sera collected in Gabon in 1981-1997. Six seropositive subjects were bled in the northeast in 1991, more than 3 years prior to recognition of the first known outbreak of Ebola haemorrhagic fever (EHF), whilst eight came from the southwest where the disease has not been recognised. It has been reported elsewhere that 98 carcasses of wild animals were found in systematic studies in northeastern Gabon and adjoining northwestern Republic of the Congo (RoC) during five EHF epidemics in August 2001 to June 2003, with Ebola virus infection being confirmed in 14 carcasses. During the present opportunistic observations, reports were investigated of a further 397 carcasses, mainly gorillas, chimpanzees, mandrills and bush pigs, found by rural residents in 35 incidents in Gabon and RoC during 1994-2003. Sixteen incidents had temporal and/or spatial coincidence with confirmed EHF outbreaks, and the remaining 19 appeared to represent extension of disease from such sites. There appeared to be sustained Ebola virus activity in the northeast in 1994-1999, with sequential spread from 1996 onwards, first westwards, then southerly, and then northeastwards, reaching the Gabon-RoC border in 2001. This implies that there was transmission of infection between wild mammals, but the species involved are highly susceptible and unlikely to be natural hosts of the virus.

Reflecting on his scientific career toward the end of his life, the French-educated medical researcher René Dubos presented his flowering as an ecological thinker as a story of linear progression—the inevitable product of the intellectual seeds planted in his youth. But how much store should we set by Dubos’s account of his ecological journey? Resisting retrospective biographical readings, this paper seeks to relate the development of Dubos’s ecological ideas to his experimental practices and his career as a laboratory researcher. In particular, I focus on Dubos’s studies of tuberculosis at the Rockefeller Institute in the period 1944–1956—studies which began with an inquiry into the tubercle bacillus and the physiochemical determinants of virulence, but which soon encompassed a wider investigation of the influence of environmental forces and host–parasite interactions on susceptibility and resistance to infection in animal models. At the same time, through a close reading of Dubos’s scientific papers and correspondence, I show how he both drew on and distinguished his ecological ideas from those of other medical researchers such as Theobald Smith, Frank Macfarlane Burnet, and Frank Fenner. However, whereas Burnet and Fenner tended to view ecological interactions at the level of populations, Dubos focused on the interface of hosts and parasites in the physiological environments of individuals. The result was that although Dubos never fully engaged with the science of ecology, he was able to incorporate ecological ideas into his thought and practices, and relate them to his holistic views on health and the natural harmony of man and his environment.

Like human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus of chimpanzees (SIVcpz) can cause CD4+ T cell loss and premature death. Here, we used molecular surveillance tools and mathematical modeling to estimate the impact of SIVcpz infection on chimpanzee population dynamics. Habituated (Mitumba and Kasekela) and non-habituated (Kalande) chimpanzees were studied in Gombe National Park, Tanzania. Ape population sizes were determined from demographic records (Mitumba and Kasekela) or individual sightings and genotyping (Kalande), while SIVcpz prevalence rates were monitored using non-invasive methods. Between 2002-2009, the Mitumba and Kasekela communities experienced mean annual growth rates of 1.9% and 2.4%, respectively, while Kalande chimpanzees suffered a significant decline, with a mean growth rate of 26.5% to 27.4%, depending on population estimates. A rapid decline in Kalande was first noted in the 1990s and originally attributed to poaching and reduced food sources. However, between 2002-2009, we found a mean SIVcpz prevalence in Kalande of 46.1%, which was almost four times higher than the prevalence in Mitumba (12.7%) and Kasekela (12.1%). To explore whether SIVcpz contributed to the Kalande decline, we used empirically determined SIVcpz transmission probabilities as well as chimpanzee mortality, mating and migration data to model the effect of viral pathogenicity on chimpanzee population growth. Deterministic calculations indicated that a prevalence of greater than 3.4% would result in negative growth and eventual population extinction, even using conservative mortality estimates. However, stochastic models revealed that in representative populations, SIVcpz, and not its host species, frequently went extinct. High SIVcpz transmission probability and excess mortality reduced population persistence, while intercommunity migration often rescued infected communities, even when immigrating females had a chance of being SIVcpz infected. Together, these results suggest that the decline of the Kalande community was caused, at least in part, by high levels of SIVcpz infection. However, population extinction is not an inevitable consequence of SIVcpz infection, but depends on additional variables, such as migration, that promote survival. These findings are consistent with the uneven distribution of SIVcpz throughout central Africa and explain how chimpanzees in Gombe and elsewhere can be at equipoise with this pathogen.