Dynamics Of Zoonotic Diseases Research Articles

Pylore Krishnaier Rajagopalan: Pioneer in Kyasanur Forest Disease Research and His Contributions to Zoonotic Disease Studies.

Pylore Krishnaier Rajagopalan was a distinguished public health expert who made significant breakthroughs in the research of Kyasanur forest disease (KFD), a prevalent tick-borne viral ailment in South India. His extensive research on KFD provided vital insights into the impact of the disease on public health and considerably advanced our knowledge of it. Rajagopalan's work also encompasses the study of zoonotic diseases, where he made substantial contributions to our understanding of their epidemiology and control. His research on KFD was instrumental in comprehending the disease transmission dynamics, clinical manifestations, and control strategies, resulting in improved management practices in regions where the disease is endemic. Rajagopalan's contributions have had a long-lasting impact on public health practices, as his work has influenced both scientific research and public health policies. The enduring effects of his work can be observed in the enhanced disease surveillance, outbreak response, and comprehension of zoonotic disease dynamics, which will continue to inform contemporary public health practices.

Landscape drives zoonotic malaria prevalence in non-human primates.

Zoonotic disease dynamics in wildlife hosts are rarely quantified at macroecological scales due to the lack of systematic surveys. Non-human primates (NHPs) host Plasmodium knowlesi, a zoonotic malaria of public health concern and the main barrier to malaria elimination in Southeast Asia. Understanding of regional P. knowlesi infection dynamics in wildlife is limited. Here, we systematically assemble reports of NHP P. knowlesi and investigate geographic determinants of prevalence in reservoir species. Meta-analysis of 6322 NHPs from 148 sites reveals that prevalence is heterogeneous across Southeast Asia, with low overall prevalence and high estimates for Malaysian Borneo. We find that regions exhibiting higher prevalence in NHPs overlap with human infection hotspots. In wildlife and humans, parasite transmission is linked to land conversion and fragmentation. By assembling remote sensing data and fitting statistical models to prevalence at multiple spatial scales, we identify novel relationships between P. knowlesi in NHPs and forest fragmentation. This suggests that higher prevalence may be contingent on habitat complexity, which would begin to explain observed geographic variation in parasite burden. These findings address critical gaps in understanding regional P. knowlesi epidemiology and indicate that prevalence in simian reservoirs may be a key spatial driver of human spillover risk.

Landscape drives zoonotic malaria prevalence in non-human primates

Zoonotic disease dynamics in wildlife hosts are rarely quantified at macroecological scales due to the lack of systematic surveys. Non-human primates (NHPs) host Plasmodium knowlesi, a zoonotic malaria of public health concern and the main barrier to malaria elimination in Southeast Asia. Understanding of regional P. knowlesi infection dynamics in wildlife is limited. Here, we systematically assemble reports of NHP P. knowlesi and investigate geographic determinants of prevalence in reservoir species. Meta-analysis of 6322 NHPs from 148 sites reveals that prevalence is heterogeneous across Southeast Asia, with low overall prevalence and high estimates for Malaysian Borneo. We find that regions exhibiting higher prevalence in NHPs overlap with human infection hotspots. In wildlife and humans, parasite transmission is linked to land conversion and fragmentation. By assembling remote sensing data and fitting statistical models to prevalence at multiple spatial scales, we identify novel relationships between P. knowlesi in NHPs and forest fragmentation. This suggests that higher prevalence may be contingent on habitat complexity, which would begin to explain observed geographic variation in parasite burden. These findings address critical gaps in understanding regional P. knowlesi epidemiology and indicate that prevalence in simian reservoirs may be a key spatial driver of human spillover risk.

Climate change and zoonotic diseases: a conceptual framework for predicting and managing health risks in the USA

The executive summary will provide a concise overview of the conceptual framework aimed at understanding the relationship between climate change and zoonotic diseases in the USA. It will highlight the significance of addressing this issue, the objectives of the framework, expected outcomes, and the proposed methodology for research and implementation. It encapsulates the essence of the proposed framework, highlighting its significance, objectives, methodology, and expected outcomes. Climate change poses a significant threat to public health, exacerbating the emergence and transmission of zoonotic diseases across the USA. This executive summary underscores the critical need for a proactive approach to understanding and managing the complex interplay between climate change and zoonotic diseases to safeguard the health of communities. The framework aims to address this pressing issue by elucidating the mechanisms through which climate change influences the dynamics of zoonotic diseases. By integrating multidisciplinary research, predictive modeling, and public health strategies, the framework seeks to enhance the nation's capacity to predict, prevent, and mitigate the health risks associated with climate change-driven zoonotic diseases. Key objectives of the framework include developing predictive models to identify high-risk areas and vulnerable populations, elucidating the pathways of disease transmission, and proposing evidence-based interventions to mitigate health risks. By fostering collaboration among researchers, policymakers, and public health practitioners, the framework aims to translate research findings into actionable strategies and policies that protect public health and promote resilience in the face of climate change. Expected outcomes of the framework include improved understanding of the complex relationship between climate change and zoonotic diseases, enhanced surveillance and early warning systems, and informed decision-making to guide public health interventions. Ultimately, the framework seeks to empower communities and decision-makers with the knowledge and tools needed to adapt to changing environmental conditions and mitigate the health impacts of zoonotic diseases in the USA.

Wildlife as sentinels for emerging zoonotic diseases: A review of surveillance systems in the USA

Wildlife plays a crucial role as sentinels for emerging zoonotic diseases, serving as early indicators of potential threats to human and animal health. This review examines the surveillance systems in the USA that utilize wildlife as indicators for the presence of emerging zoonotic pathogens. The review focuses on the methodologies, challenges, and implications of these surveillance systems. In the USA, wildlife surveillance for zoonotic diseases is primarily conducted through passive surveillance, where wildlife carcasses are collected and tested for pathogens. Additionally, active surveillance programs target specific wildlife species known to host zoonotic pathogens or species that may be in close contact with humans or domestic animals. These surveillance efforts are complemented by the use of sentinel species, such as birds or bats, which are monitored for signs of disease that could indicate the presence of zoonotic pathogens. Challenges in wildlife surveillance include the vast geographic range of many wildlife species, making it difficult to sample populations comprehensively. Additionally, the diversity of wildlife species and habitats in the USA presents logistical challenges for surveillance efforts. Furthermore, there are challenges related to data sharing and coordination among agencies responsible for wildlife and public health. The implications of wildlife surveillance for public health policy and practice are significant. Early detection of zoonotic pathogens in wildlife can lead to timely public health interventions, such as vaccination campaigns or changes in land use practices to reduce human-wildlife contact. Moreover, wildlife surveillance can inform the development of predictive models for disease outbreaks, enabling more effective preparedness and response measures. In conclusion, wildlife surveillance plays a critical role in the early detection and monitoring of emerging zoonotic diseases in the USA. Continued investment in surveillance systems and research is essential to enhance our understanding of zoonotic disease dynamics and improve our ability to protect human and animal health.

Molecular detection of Borrelia spp. (Spirochaetales: Borreliaceae) in ticks (Acari: Ixodidae) collected from tortoises in Java, Indonesia

Abstract. Sophia HF, Supriyono, Soviana S, Novianto D, Hadi UK. 2023. Molecular detection of Borrelia spp. (Spirochaetales: Borreliaceae) in ticks (Acari: Ixodidae) collected from tortoises in Java, Indonesia. Biodiveritas 24: 6852-6857. Reptiles are known hosts of various tick species, many of which are zoonotic and pose veterinary and public health risks. Amblyomma ticks frequently parasitize reptiles and are potential vectors of zoonoses. This study aimed to investigate the prevalence of tick infestations and to identify Borrelia species infections in ticks found on tortoises. One hundred six tortoise hosts in three provinces in Indonesia. DNA extraction and Borrelia species were detected using conventional PCR techniques. The results revealed the presence of nineteen hard-bodied ticks on Chelonoidis carbonarius Spix, 1824, Chelonoidis denticulatus Linnaeus, 1766, and Geochelone sulcata Miller, 1779. All the ticks collected were identified as Amblyomma sparsum Neumann 1899, and the prevalence of A. sparsum infestations on tortoises in this study was 7.55%. Borrelia spp. was detected in some of the A. sparsum ticks infesting tortoises. Subsequent sequencing unveiled two distinct reptile-associated (REP) borrelia strains. This study sheds light on the tick infestation patterns and the potential transmission of Borrelia species among tortoises kept as exotic pets in urban areas by A. sparsum ticks. The findings provide valuable insights into the bioecology of ticks and the associated health risks they pose to reptiles, thereby contributing to our understanding of zoonotic disease dynamics in the region.

Transmission Dynamics of Zoonotic Diseases from Forest to Cities

Transmission Dynamics of Zoonotic Diseases from Forest to Cities

Zoonoses in the margins: environmental displacement and health outcomes in the Indus Delta

BackgroundIt remains unclear how human and animal displacement impacts zoonotic disease risk with little contextualized primary data available. This study investigates zoonotic disease dynamics in populations regularly displaced due to slow onset disasters and annual monsoons in the Indus Delta in Sindh province in southeast Pakistan.MethodsUsing a case study methodology, semi-structured key informant interviews and focus group discussions with 35 participants, as well as observational studies were conducted in seven communities in Thatta district.ResultsKey factors affecting zoonotic disease dynamics in environmental displacement in Thatta identified in the study include disasters and loss of forage, a lack of veterinary and healthcare access, and socio-economic status. Animal and human health are an important consideration in displacement disrupting communities and livelihoods, affecting safety, health, and food security. Displacement results in a poverty spiral whereby the displaced find themselves at continuous peril from poverty and disaster, with zoonotic disease dynamics shifting based on environmental changes, and an expectation of future movement and loss.ConclusionThe precarious conditions generated through the disruption of communities and livelihoods makes environmentally displaced populations vulnerable to zoonotic disease. To prevent further displacement and disease, broader political economy issues need to be addressed, and comprehensive assistance provided to support sustainable livelihoods.

A robust study of the transmission dynamics of zoonotic infection through non-integer derivative

Abstract In Sub-Saharan Africa, zoonotic diseases are the leading cause of sickness and mortality, yet preventing their spread has long been difficult. Vaccination initiatives have significantly reduced the frequency of zoonotic diseases mostly in African regions. Nonetheless, zoonotic illnesses continue to be a hazard to underdeveloped countries. Zoonotic infections are spread by direct contact, food, and water. We construct an epidemic model to understand zoonotic disease transmission phenomena. The model is examined using the fundamental results of fractional theory. The reproduction parameter ℛ 0 {{\mathcal{ {\mathcal R} }}}_{0} was obtained by inspecting the model’s steady states. The stability of the system’s steady states has been demonstrated. The system’s reproduction parameter is quantitatively explored by varying various input parameters. Furthermore, the presence and uniqueness of the solution of the proposed dynamics of zoonotic diseases have been demonstrated. Different simulations of the recommended zoonotic disease model with different input factors are performed to inspect the complex dynamics of zoonotic disease with the influence of various model factors. To establish effective prevention and control measures for the infection, we analyse dynamical behaviour of the system. Decreasing the fractional order θ \theta can decrease the infection level significantly. Different factors for reducing zoonotic diseases were recommended to regional policymakers.

Excluding Livestock Livelihoods in Refugee Responses: A Risk to Public Health

Abstract The Syrian civil war caused a near total collapse of its health and veterinary infrastructure, affecting vaccinations, quarantine and border control. While outbreaks of zoonoses—diseases transmissible between animals and humans—in neighbouring countries are attributed to irregular cross-border movements, little remains known about the impact of conflict and displacement on livestock, and zoonotic disease risks in refugee and host populations. This case study investigates the role of livestock and zoonotic disease dynamics in the Syrian refugee context in Jordan, to inform policies and procedures for better inclusion of livestock in refugee responses. Key informant interviews were conducted with humanitarian, animal and public health experts, and household interviews with Jordanian and Syrian livestock keepers in Mafraq Governorate. Respondents attributed zoonotic disease outbreaks to cross-border smuggling of livestock, with no reports of refugees bringing animals into Jordan. While Syrian respondents diversify their livelihoods through animal husbandry, high-level political and practical barriers affect refugees’ access to livestock assistance, increasing zoonotic disease risks. To support animal and human health, stakeholders need to address structural inequalities through inclusive policies and support to both refugees and host populations.

Nonstandard finite difference method of modelling zoonotic diseases

Zoonotic diseases are mostly the leading causes of illness and deaths in Sub-Saharan Africa but efforts to combat the spread of these diseases has always been a challenge. Incidence of zoonotic diseases has reduced substantially in most parts of Africa as a result of rigorous vaccination campaigns. However, zoonotic diseases still remain a threat to developing nations. Zoonotic diseases can be contracted either by direct contact, food and water. In this paper, we developed and analysed a general model that explains the dynamics of zoonotic diseases and analysed it using nonstantard finite difference approach. This scheme was used for the model analysis. The disease free equilibrium of the scheme in its explicit form was determined and it was both locally and globally asymptotically stable. Bifurcation and multiple equilibria as well as the threshold value for disease transmission was determined. An analysis of the effects of contact between susceptible and infected animals as well susceptible and infected humans was conducted. It showed an increase in infected animals and humans whenever the contact rate increases and decreases otherwise. The epidemiological implication is that zoonotic disease can be controlled by ensuring that interactions between susceptible humans, infected animals and infected humans is reduced to the bearest minimum.

Disaster displacement and zoonotic disease dynamics: The impact of structural and chronic drivers in Sindh, Pakistan.

Projected increases in human and animal displacement driven by climate change, disasters and related environmental degradation will have significant implications to global health. Pathways for infectious disease transmission including zoonoses, diseases transmitted between animals and humans, are complex and non-linear. While forced migration is considered an important driver for the spread of zoonoses, actual disease dynamics remain under researched. This paper presents the findings of a case study investigating how disaster displacement affected zoonotic disease transmission risk following the 2010 'superfloods' in Sindh province, Pakistan. We interviewed 30 key informants and 17 household members across 6 rural communities between March and November 2019, supported by observational studies and a review of secondary data. Results were analysed using the ecosocial theoretical framework. Buffalo, cattle and goats were often the only moveable asset, therefore livestock was an important consideration in determining displacement modality and destination location, and crowded locations were avoided to protect human and animal health. Meanwhile however, livestock was rarely included in the humanitarian response, resulting in communities and households fragmenting according to the availability of livestock provisions. We found that rather than a driver for disease, displacement acted as a process affecting community, household and individual zoonotic disease risk dynamics, based on available resources and social networks before, during and after displacement, rooted in the historical, political and socio-economic context. We conclude that in rural Sindh, disaster displaced populations' risk of zoonoses is the result of changes in dynamics rooted in pre-existing structural and chronic inequalities, making people more or less vulnerable to disease through multiple interlinked pathways. Our findings have implications for policy makers and humanitarian responders assisting displaced populations dependent on livestock, with a call to integrate livestock support in humanitarian policies and responses for health, survival and recovery.

Co-occurrence of and risk factors for Cryptosporidium and Giardia in brown rats from Buenos Aires, Argentina.

A rodent survey was conducted in different landscape units of the city of Buenos Aires (Argentina) to determine the prevalence of Cryptosporidium and Giardia in Rattus norvegicus and to, ultimately, assess the biotic, environmental and meteorological factors that explain the variations of the likelihood of infection for both parasites in an urban environment. The results of this study revealed a ubiquitous presence of Cryptosporidium and Giardia in R.norvegicus within an urban environment with the likelihood of infection depending on environmental and meteorological conditions for both parasites. The overall prevalence was greater for Cryptosporidium (p=50.4%) than for Giardia (20.3%). The prevalence for both parasites separately was higher in parks compared to shantytowns and scrap metal yards. Generalized Linear Mixed Models revealed that the occurrence of these parasites separately, at an individual level, was positively related with rainfall variables and that the effect of temperature depended on the landscape unit. The similarities in the transmission modes, which are affected by common extrinsic factors, may facilitate the co-occurrence of Cryptosporidium and Giardia in urban rats. Rattus norvegicus is recognized as a good model for epidemiological studies and the results of this work suggest that, from an epidemiological point of view, the probability of contact with infectious oocysts and cysts of these parasites can be modulated through environmental management and healthy behaviour towards risk factors. The information presented here will be useful to improve the understanding of the dynamics of zoonotic diseases within urban environments and to contribute to the decision-making of new and effective prophylactic measures.

Zoonotic disease transmission risks in displacement

BackgroundThe novel coronavirus pandemic reiterates the risk of zoonoses - diseases transmittable between animals and humans - to global health. Meanwhile, climate change and conflict increasingly cause human and animal movement, affecting interspecies, intrahuman and interhuman barriers to disease. The dynamics and risks of zoonotic diseases among naive (host) populations and displaced communities are not well understood. This study aims to determine how displacement affects the vulnerability of displaced populations to zoonotic disease transmission, to improve policy development and humanitarian responses.MethodsFollowing a literature review, countries for fieldwork were selected and visited based on zoonotic disease risk, livestock dependency and population displacement. Expert interviews were conducted in Jordan and Pakistan with policy makers and responders in public health, livestock and disaster management, and household interviews conducted with displaced. Data was analyzed using a conceptual framework considering biological, environmental, technological, social and political processes at national, local and individual level.ResultsPoverty and low socio-economic status are considered main determinants of people's vulnerability to disease, while disasters affect health services and staff, as well as disease pathogen, vector and host environments. Displacement exacerbates these risks, including the availability of water and sanitation, shelter and population density. The formal or informal status of refugees and internal displaced people influences their access to services, further affecting their health. Meanwhile, zoonotic disease dynamics are not sufficiently understood among stakeholders, and animals remain an afterthought in many humanitarian responses.ConclusionsZoonoses in displacement settings need to be addressed using a transdisciplinary, multilevel approach, addressing disease as well as underlying political, social and economic risk factors.Key messages Zoonotic disease transmission depends on complex ecological, political and socio-economic drivers, therefore zoonotic disease risk in displacement requires a multilevel, transdisciplinary approach.Among rural populations dependent on livestock, the presence of endemic zoonotic pathogens is likely to be constant. Displacement may increase disease risk by affecting animal and human immunity.

Assessing the Impact of Optimal Health Education Programs on the Control of Zoonotic Diseases.

To better understand the dynamics of zoonotic diseases, we propose a deterministic mathematical model to study the dynamics of zoonotic brucellosis with a focus on developing countries. The model contains all the relevant biological details, including indirect transmission by the environment. We analyze the essential dynamic behavior of the model and perform an optimal control study to design effective prevention and intervention strategies. The sensitivity analysis of the model parameters is performed. The aim of the controls is tied to reducing the number of infected humans, through health promotional programs within the affected communities. The Pontryagin's Maximum Principle is used to characterize the optimal level of the controls, and the resulting optimality system is solved numerically. Overall, the study demonstrates that through health promotional programs on zoonotic diseases among villagers, it is vital that they should be conducted with high efficacy.

Population genetics of fruit bat reservoir informs the dynamics, distribution and diversity of Nipah virus.

The structure and connectivity of wildlife host populations may influence zoonotic disease dynamics, evolution and therefore spillover risk to people. Fruit bats in the genus Pteropus, or flying foxes, are the primary natural reservoir for henipaviruses-a group of emerging paramyxoviruses that threaten livestock and public health. In Bangladesh, Pteropus medius is the reservoir for Nipah virus-and viral spillover has led to human fatalities nearly every year since 2001. Here, we use mitochondrial DNA and nuclear microsatellite markers to measure the population structure, demographic history and phylogeography of P.medius in Bangladesh. We combine this with a phylogeographic analysis of all known Nipah virus sequences and strains currently available to better inform the dynamics, distribution and evolutionary history of Nipah virus. We show that P.medius is primarily panmictic, but combined analysis of microsatellite and morphological data shows evidence for differentiation of two populations in eastern Bangladesh, corresponding to a divergent strain of Nipah virus also found in bats from eastern Bangladesh. Our demographic analyses indicate that a large, expanding population of flying foxes has existed in Bangladesh since the Late Pleistocene, coinciding with human population expansion in South Asia, suggesting repeated historical spillover of Nipah virus likely occurred. We present the first evidence of mitochondrial introgression, or hybridization, between P.medius and flying fox species found in South-East Asia (P.vampyrus and P.hypomelanus), which may help to explain the distribution of Nipah virus strains across the region.

Transmission dynamics of re-emerging rabies in domestic dogs of rural China.

Despite ongoing efforts to control transmission, rabies prevention remains a challenge in many developing countries, especially in rural areas of China where re-emerging rabies is under-reported due to a lack of sustained animal surveillance. By taking advantage of detailed genomic and epidemiological data for the re-emerging rabies outbreak in Yunnan Province, China, collected between 1999 and 2015, we reconstruct the demographic and dispersal history of domestic dog rabies virus (RABV) as well as the dynamics of dog-to-dog and dog-to-human transmission. Phylogeographic analyses reveal a lower diffusion coefficient than previously estimated for dog RABV dissemination in northern Africa. Furthermore, epidemiological analyses reveal transmission rates between dogs, as well as between dogs and humans, lower than estimates for Africa. Finally, we show that reconstructed epidemic history of RABV among dogs and the dynamics of rabid dogs are consistent with the recorded human rabies cases. This work illustrates the benefits of combining phylogeographic and epidemic modelling approaches for uncovering the spatiotemporal dynamics of zoonotic diseases, with both approaches providing estimates of key epidemiological parameters.

Interacting effects of wildlife loss and climate on ticks and tick-borne disease.

Both large-wildlife loss and climatic changes can independently influence the prevalence and distribution of zoonotic disease. Given growing evidence that wildlife loss often has stronger community-level effects in low-productivity areas, we hypothesized that these perturbations would have interactive effects on disease risk. We experimentally tested this hypothesis by measuring tick abundance and the prevalence of tick-borne pathogens (Coxiella burnetii and Rickettsia spp.) within long-term, size-selective, large-herbivore exclosures replicated across a precipitation gradient in East Africa. Total wildlife exclusion increased total tick abundance by 130% (mesic sites) to 225% (dry, low-productivity sites), demonstrating a significant interaction of defaunation and aridity on tick abundance. When differing degrees of exclusion were tested for a subset of months, total tick abundance increased from 170% (only mega-herbivores excluded) to 360% (all large wildlife excluded). Wildlife exclusion differentially affected the abundance of the three dominant tick species, and this effect varied strongly over time, likely due to differences among species in their host associations, seasonality, and other ecological characteristics. Pathogen prevalence did not differ across wildlife exclusion treatments, rainfall levels, or tick species, suggesting that exposure risk will respond to defaunation and climate change in proportion to total tick abundance. These findings demonstrate interacting effects of defaunation and aridity that increase disease risk, and they highlight the need to incorporate ecological context when predicting effects of wildlife loss on zoonotic disease dynamics.

Economic factors influencing zoonotic disease dynamics: demand for poultry meat and seasonal transmission of avian influenza in Vietnam

While climate is often presented as a key factor influencing the seasonality of diseases, the importance of anthropogenic factors is less commonly evaluated. Using a combination of methods – wavelet analysis, economic analysis, statistical and disease transmission modelling – we aimed to explore the influence of climatic and economic factors on the seasonality of H5N1 Highly Pathogenic Avian Influenza in the domestic poultry population of Vietnam. We found that while climatic variables are associated with seasonal variation in the incidence of avian influenza outbreaks in the North of the country, this is not the case in the Centre and the South. In contrast, temporal patterns of H5N1 incidence are similar across these 3 regions: periods of high H5N1 incidence coincide with Lunar New Year festival, occurring in January-February, in the 3 climatic regions for 5 out of the 8 study years. Yet, daily poultry meat consumption drastically increases during Lunar New Year festival throughout the country. To meet this rise in demand, poultry production and trade are expected to peak around the festival period, promoting viral spread, which we demonstrated using a stochastic disease transmission model. This study illustrates the way in which economic factors may influence the dynamics of livestock pathogens.

Early animal farming and zoonotic disease dynamics: modelling brucellosis transmission in Neolithic goat populations.

Zoonotic pathogens are frequently hypothesized as emerging with the origins of farming, but evidence of this is elusive in the archaeological records. To explore the potential impact of animal domestication on zoonotic disease dynamics and human infection risk, we developed a model simulating the transmission of Brucella melitensis within early domestic goat populations. The model was informed by archaeological data describing goat populations in Neolithic settlements in the Fertile Crescent, and used to assess the potential of these populations to sustain the circulation of Brucella. Results show that the pathogen could have been sustained even at low levels of transmission within these domestic goat populations. This resulted from the creation of dense populations and major changes in demographic characteristics. The selective harvesting of young male goats, likely aimed at improving the efficiency of food production, modified the age and sex structure of these populations, increasing the transmission potential of the pathogen within these populations. Probable interactions between Neolithic settlements would have further promoted pathogen maintenance. By fostering conditions suitable for allowing domestic goats to become reservoirs of Brucella melitensis, the early stages of agricultural development were likely to promote the exposure of humans to this pathogen.