Use of infrared camera to understand bats' access to date palm sap: implications for preventing Nipah virus transmission

Nipah Virus: A Multidimensional Update

Nipah virus (NiV) is an emerging zoonotic paramyxovirus to which is attributed numerous high mortality outbreaks in South and South-East Asia; Bangladesh's Nipah belt accounts for the vast majority of human outbreaks, reporting regular viral emergency events. The natural reservoir of NiV is the Pteropus bat species, which covers a wide geographical distribution extending over Asia, Oceania, and Africa. Occasionally, human outbreaks have required the presence of an intermediate amplification mammal host between bat and humans. However, in Bangladesh, the viral transmission occurs directly from bat to human mainly by ingestion of contaminated fresh date palm sap. Human infection manifests as a rapidly progressive encephalitis accounting for extremely high mortality rates. Despite that, no therapeutic agents or vaccines have been approved for human use. An updated review of the main NiV infection determinants and current potential therapeutic and preventive strategies is exposed.

Emerging and re-emerging pediatric viral diseases: a continuing global challenge

The twenty-first century has been marked by a surge in viral epidemics and pandemics, highlighting the global health challenge posed by emerging and re-emerging pediatric viral diseases. This review article explores the complex dynamics contributing to this challenge, including climate change, globalization, socio-economic interconnectedness, geopolitical tensions, vaccine hesitancy, misinformation, and disparities in access to healthcare resources. Understanding the interactions between the environment, socioeconomics, and health is crucial for effectively addressing current and future outbreaks. This scoping review focuses on emerging and re-emerging viral infectious diseases, with an emphasis on pediatric vulnerability. It highlights the urgent need for prevention, preparedness, and response efforts, particularly in resource-limited communities disproportionately affected by climate change and spillover events. Adopting a One Health/Planetary Health approach, which integrates human, animal, and ecosystem health, can enhance equity and resilience in global communities. IMPACT: We provide a scoping review of emerging and re-emerging viral threats to global pediatric populations This review provides an update on current pediatric viral threats in the context of the COVID-19 pandemic This review aims to sensitize clinicians, epidemiologists, public health practitioners, and policy stakeholders/decision-makers to the role these viral diseases have in persistent pediatric morbidity and mortality.

Recently Emerged Novel Henipa-like Viruses: Shining a Spotlight on the Shrew

Henipaviruses are zoonotic viruses, including some highly pathogenic and capable of serious disease and high fatality rates in both animals and humans. Hendra virus and Nipah virus are the most notable henipaviruses, resulting in significant outbreaks across South Asia, South-East Asia, and Australia. Pteropid fruit bats have been identified as key zoonotic reservoirs; however, the increased discovery of henipaviruses outside the geographic distribution of Pteropid fruit bats and the detection of novel henipa-like viruses in other species such as the shrew, rat, and opossum suggest that Pteropid bats are not the sole reservoir for henipaviruses. In this review, we provide an update on henipavirus spillover events and describe the recent detection of novel unclassified henipaviruses, with a strong focus on the shrew and its emerging role as a key host of henipaviruses.

Trends in Bacterial Pathogens of Bats: Global Distribution and Knowledge Gaps

Bats have received considerable recent attention for infectious disease research because of their potential to host and transmit viruses, including Ebola, Hendra, Nipah, and multiple coronaviruses. These pathogens are occasionally transmitted from bats to wildlife, livestock, and to humans, directly or through other bridging (intermediate) hosts. Due to their public health relevance, zoonotic viruses are a primary focus of research attention. In contrast, other emerging pathogens of bats, such as bacteria, are vastly understudied despite their ubiquity and diversity. Here, we describe the currently known host ranges and geographic distributional patterns of potentially zoonotic bacterial genera in bats, using published presence-absence data of pathogen occurrence. We identify apparent gaps in our understanding of the distribution of these pathogens on a global scale. The most frequently detected bacterial genera in bats are Bartonella, Leptospira, and Mycoplasma. However, a wide variety of other potentially zoonotic bacterial genera are also occasionally found in bats, such as Anaplasma, Brucella, Borrelia, Coxiella, Ehrlichia, Francisella, Neorickettsia, and Rickettsia. The bat families Phyllostomidae, Vespertilionidae, and Pteropodidae are most frequently reported as hosts of bacterial pathogens; however, the presence of at least one bacterial genus was confirmed in all 15 bat families tested. On a spatial scale, molecular diagnostics of samples from 58 countries and four overseas departments and island states (French Guiana, Mayotte, New Caledonia, and Réunion Island) reported testing for at least one bacterial pathogen in bats. We also identified geographical areas that have been mostly neglected during bacterial pathogen research in bats, such as the Afrotropical region and Southern Asia. Current knowledge on the distribution of potentially zoonotic bacterial genera in bats is strongly biased by research effort towards certain taxonomic groups and geographic regions. Identifying these biases can guide future surveillance efforts, contributing to a better understanding of the ecoepidemiology of zoonotic pathogens in bats.

Human Exposure to Bats, Rodents and Monkeys in Bangladesh

Bats, rodents and monkeys are reservoirs for emerging zoonotic infections. We sought to describe the frequency of human exposure to these animals and the seasonal and geographic variation of these exposures in Bangladesh. During 2013-2016, we conducted a cross-sectional survey in a nationally representative sample of 10,002 households from 1001 randomly selected communities. We interviewed household members about exposures to bats, rodents and monkeys, including a key human-bat interface-raw date palm sap consumption. Respondents reported observing rodents (90%), bats (52%) and monkeys (2%) in or around their households, although fewer reported direct contact. The presence of monkeys around the household was reported more often in Sylhet division (7%) compared to other divisions. Households in Khulna (17%) and Rajshahi (13%) were more likely to report drinking date palm sap than in other divisions (1.5-5.6%). Date palm sap was mostly consumed during winter with higher frequencies in January (16%) and February (12%) than in other months (0-5.6%). There was a decreasing trend in drinking sap over the three years. Overall, we observed substantial geographic and seasonal patterns in human exposure to animals that could be sources of zoonotic disease. These findings could facilitate targeting emerging zoonoses surveillance, research and prevention efforts to areas and seasons with the highest levels of exposure.

Nipah Virus Disease: Epidemiological, Clinical, Diagnostic and Legislative Aspects of This Unpredictable Emerging Zoonosis

Nipah virus (NiV) infection is a viral disease caused by a Henipavirus, belonging to the Paramyxoviridae family, responsible for a zoonosis. The course of the disease can be very serious and lead to death. NiV natural hosts are fruit bats (also known as megabats) belonging to the Pteropodidae family, especially those of the Pteropus genus. Natural infection in domestic animals has been described in farming pigs, horses, domestic and feral dogs and cats. Natural NiV transmission is possible intra-species (pig-to-pig, human-to-human) and inter-species (flying bat-to-human, pig-to-human, horse-to-human). The infection can be spread by humans or animals in different ways. It is peculiar how the viral transmission modes among different hosts also change depending on the geographical area for different reasons, including different breeding methods, eating habits and the recently identified genetic traits/molecular features of main virus proteins related to virulence. Outbreaks have been described in Malaysia, Singapore, Bangladesh, India and the Philippines with, in some cases, severe respiratory and neurological disease and high mortality in both humans and pigs. Diagnosis can be made using different methods including serological, molecular, virological and immunohistochemical methods. The cornerstones for control of the disease are biosecurity (via the correct management of reservoir and intermediate/amplifying hosts) and potential vaccines which are still under development. However, the evaluation of the potential influence of climate and anthropogenic changes on the NiV reservoir bats and their habitat as well as on disease spread and inter-specific infections is of great importance. Bats, as natural reservoirs of the virus, are responsible for the viral spread and, therefore, for the outbreaks of the disease in humans and animals. Due to the worldwide distribution of bats, potential new reports and spillovers are not to be dismissed in the future.

Global patterns of phylogenetic diversity and transmission of bat coronavirus

Bats are reservoirs for multiple coronaviruses (CoVs). However, the phylogenetic diversity and transmission of global bat-borne CoVs remain poorly understood. Here, we performed a Bayesian phylogeographic analysis based on 3,594 bat CoV RdRp gene sequences to study the phylogenetic diversity and transmission of bat-borne CoVs and the underlying driving factors. We found that host-switching events occurred more frequently for α-CoVs than for β-CoVs, and the latter was highly constrained by bat phylogeny. Bat species in the families Molossidae, Rhinolophidae, Miniopteridae, and Vespertilionidae had larger contributions to the cross-species transmission of bat CoVs. Regions of eastern and southern Africa, southern South America, Western Europe, and Southeast Asia were more frequently involved in cross-region transmission events of bat CoVs than other regions. Phylogenetic and geographic distances were the most important factors limiting CoV transmission. Bat taxa and global geographic hotspots associated with bat CoV phylogenetic diversity were identified, and bat species richness, mean annual temperature, global agricultural cropland, and human population density were strongly correlated with the phylogenetic diversity of bat CoVs. These findings provide insight into bat CoV evolution and ecological transmission among bat taxa. The identified hotspots of bat CoV evolution and transmission will guide early warnings of bat-borne CoV zoonotic diseases.

Henipaviruses: an expanding global public health concern?

Nipah virus (NiV) and Hendra virus (HeV) are highly pathogenic zoonotic viruses of the genus Henipavirus, family Paramyxoviridae that cause severe disease outbreaks in humans and also can infect and cause lethal disease across a broad range of mammalian species. Another related Henipavirus has been very recently identified in China in febrile patients with pneumonia, the Langya virus (LayV) of probable animal origin in shrews. NiV and HeV were first identified as the causative agents of severe respiratory and encephalitic disease in the 1990s across Australia and Southern Asia with mortality rates reaching up to 90%. They are responsible for rare and sporadic outbreaks with no approved treatment modalities. NiV and HeV have wide cellular tropism that contributes to their high pathogenicity. From their natural hosts bats, different scenarios propitiate their spillover to pigs, horses, and humans. Henipavirus-associated respiratory disease arises from vasculitis and respiratory epithelial cell infection while the neuropathogenesis of Henipavirus infection is still not completely understood but appears to arise from dual mechanisms of vascular disease and direct parenchymal brain infection. This brief review offers an overview of direct and indirect mechanisms of HeV and NiV pathogenicity and their interaction with the human immune system, as well as the main viral strategies to subvert such responses.

Nipah Virus Detection at Bat Roosts after Spillover Events, Bangladesh, 2012-2019

Knowledge of the dynamics and genetic diversity of Nipah virus circulating in bats and at the human-animal interface is limited by current sampling efforts, which produce few detections of viral RNA. We report a series of investigations at Pteropus medius bat roosts identified near the locations of human Nipah cases in Bangladesh during 2012–2019. Pooled bat urine was collected from 23 roosts; 7 roosts (30%) had >1 sample in which Nipah RNA was detected from the first visit. In subsequent visits to these 7 roosts, RNA was detected in bat urine up to 52 days after the presumed exposure of the human case-patient, although the probability of detection declined rapidly with time. These results suggest that rapidly deployed investigations of Nipah virus shedding from bat roosts near human cases could increase the success of viral sequencing compared with background surveillance and could enhance understanding of Nipah virus ecology and evolution.

The Immunobiology of Nipah Virus

Nipah virus (NiV) is a highly lethal zoonotic paramyxovirus that emerged in Malaysia in 1998. It is a human pathogen capable of causing severe respiratory infection and encephalitis. The natural reservoir of NiV, Pteropus fruit bats, remains a continuous virus source for future outbreaks, although infection in the bats is largely asymptomatic. NiV provokes serious disease in various mammalian species. In the recent human NiV outbreaks in Bangladesh and India, both bats-to-human and human-to-human transmissions have been observed. NiV has been demonstrated to interfere with the innate immune response via interferon type I signaling, promoting viral dissemination and preventing antiviral response. Studies of humoral immunity in infected NiV patients and animal models have shown that NiV-specific antibodies were produced upon infection and were protective. Studies on cellular immunity response to NiV infection in human and animal models also found that the adaptive immune response, specifically CD4+ and CD8+ T cells, was stimulated upon NiV infection. The experimental vaccines and therapeutic strategies developed have provided insights into the immunological requirements for the development of successful medical countermeasures against NiV. This review summarizes the current understanding of NiV pathogenesis and innate and adaptive immune responses induced upon infection.

Henipavirus Immune Evasion and Pathogenesis Mechanisms: Lessons Learnt from Natural Infection and Animal Models

Nipah henipavirus (NiV) and Hendra henipavirus (HeV) are zoonotic emerging paramyxoviruses causing severe disease outbreaks in humans and livestock, mostly in Australia, India, Malaysia, Singapore and Bangladesh. Both are bat-borne viruses and in humans, their mortality rates can reach 60% in the case of HeV and 92% for NiV, thus being two of the deadliest viruses known for humans. Several factors, including a large cellular tropism and a wide zoonotic potential, con-tribute to their high pathogenicity. This review provides an overview of HeV and NiV pathogenicity mechanisms and provides a summary of their interactions with the immune systems of their different host species, including their natural hosts bats, spillover-hosts pigs, horses, and humans, as well as in experimental animal models. A better understanding of the interactions between henipaviruses and their hosts could facilitate the development of new therapeutic strategies and vaccine measures against these re-emerging viruses.

Ecological Barrier Deterioration Driven by Human Activities Poses Fatal Threats to Public Health due to Emerging Infectious Diseases

The coronavirus disease 2019 (COVID-19) and concerns about several other pandemics in the 21st century have attracted extensive global attention. These emerging infectious diseases threaten global public health and raise urgent studies on unraveling the underlying mechanisms of their transmission from animals to humans. Although numerous works have intensively discussed the cross-species and endemic barriers to the occurrence and spread of emerging infectious diseases, both types of barriers play synergistic roles in wildlife habitats. Thus far, there is still a lack of a complete understanding of viral diffusion, migration, and transmission in ecosystems from a macro perspective. In this review, we conceptualize the ecological barrier that represents the combined effects of cross-species and endemic barriers for either the natural or intermediate hosts of viruses. We comprehensively discuss the key influential factors affecting the ecological barrier against viral transmission from virus hosts in their natural habitats into human society, including transmission routes, contact probability, contact frequency, and viral characteristics. Considering the significant impacts of human activities and global industrialization on the strength of the ecological barrier, ecological barrier deterioration driven by human activities is critically analyzed for potential mechanisms. Global climate change can trigger and expand the range of emerging infectious diseases, and human disturbances promote higher contact frequency and greater transmission possibility. In addition, globalization drives more transmission routes and produces new high-risk regions in city areas. This review aims to provide a new concept for and comprehensive evidence of the ecological barrier blocking the transmission and spread of emerging infectious diseases. It also offers new insights into potential strategies to protect the ecological barrier and reduce the wide-ranging risks of emerging infectious diseases to public health.

Seasonality of Date Palm Sap Feeding Behavior by Bats in Bangladesh

Pteropus bats are the natural reservoir for Nipah virus, and in Bangladesh, it is transmitted to people through consumption of raw or fermented date palm sap. Our objective was to understand seasonal patterns of bat feeding on date palm sap at a location where sap is collected year-round. Seven nights each month over three years, we mounted infrared cameras in four trees to observe bats' feeding behavior at date palm trees harvested for fermented sap production. We described the frequency of bat visits, duration of bat visits, and duration of bat-sap contact by month and by year. We captured 42,873 bat visits during 256 camera-nights of observation, of which 3% were Pteropus and 94% were non-Pteropus bats. Though the frequency of Pteropus bat visits to each tree/night was much lower than non-Pteropus bat visits, Pteropus bats stayed in contact with sap longer than non-Pteropus bats. Frequency of bat visits was higher during winter compared to other seasons, which may arise as a consequence of limited availability of food sources during this period or may be related to seasonal characteristics of the sap. Seasonal alignment of sap consumption by humans and bats may have consequences for viral spillover into humans.

Common Themes in Zoonotic Spillover and Disease Emergence: Lessons Learned from Bat- and Rodent-Borne RNA Viruses

Rodents (order Rodentia), followed by bats (order Chiroptera), comprise the largest percentage of living mammals on earth. Thus, it is not surprising that these two orders account for many of the reservoirs of the zoonotic RNA viruses discovered to date. The spillover of these viruses from wildlife to human do not typically result in pandemics but rather geographically confined outbreaks of human infection and disease. While limited geographically, these viruses cause thousands of cases of human disease each year. In this review, we focus on three questions regarding zoonotic viruses that originate in bats and rodents. First, what biological strategies have evolved that allow RNA viruses to reside in bats and rodents? Second, what are the environmental and ecological causes that drive viral spillover? Third, how does virus spillover occur from bats and rodents to humans?

Vaccines to Emerging Viruses: Nipah and Hendra

Hendra virus (HeV) and Nipah virus (NiV) are bat-borne zoonotic para-myxoviruses identified in the mid- to late 1990s in outbreaks of severe disease in livestock and people in Australia and Malaysia, respectively. HeV repeatedly re-emerges in Australia while NiV continues to cause outbreaks in South Asia (Bangladesh and India), and these viruses have remained transboundary threats. In people and several mammalian species, HeV and NiV infections present as a severe systemic and often fatal neurologic and/or respiratory disease. NiV stands out as a potential pandemic threat because of its associated high case-fatality rates and capacity for human-to-human transmission. The development of effective vaccines, suitable for people and livestock, against HeV and NiV has been a research focus. Here, we review the progress made in NiV and HeV vaccine development, with an emphasis on those approaches that have been tested in established animal challenge models of NiV and HeV infection and disease.

[Bats of the subtropical climate zone of the Krasnodar Territory of Russia as a possible reservoir of zoonotic viral infections]

Emerging and reemerging infections pose a grave global health threat. The emergence of the SARS-CoV-2 virus and the resulting COVID-19 pandemic have demonstrated the importance of studying of zoonotic viruses directly in natural foci. For SARS-like coronaviruses, as well as for many other zoonotic pathogens (including hemorrhagic fevers and rabies agents), the main reservoir are horseshoe bats (Rhinolophus spp.), which are widely distributed in Eurasia and Africa. Their range also covers the southern regions of Russia, including the North Caucasus and Crimea. Large colonies of these animals are located on the territory of Sochi National Park (SNP; subtropical zone of Krasnodar Territory, Greater Sochi region, North Caucasus). In total, according to long-term observations, up to 23 species of bats were registered here, including the great (Rh. ferrumequinum), the lesser (Rh. hipposideros), and the Mediterranean (Rh. euryale) horseshoe bats.This review provides information on zoonotic viruses associated with species of bats distributed in the subtropical zone of Krasnodar Territory of Russia, and analyzes their possible role as a natural reservoir of emerging and reemerging infections. Studying the circulation of zoonotic viruses in bats is an important element of monitoring viral populations in natural foci.

Hitchhiking microbes: Declining biodiversity & emerging zoonoses

The connection between nature conservation and human wellbeing is well known, however, the role of declining biodiversity and emerging diseases is relatively less studied. The presence of a thriving biological diversity is known to have therapeutic effects on human health. On the other hand, human economic activities have contributed to a sharp decline in species, resulting in poor ecosystem health. Several studies have shown how microorganisms have switched from animals to humans, leading to novel diseases. This review describes studies on zoonotic diseases and biodiversity, with examples from India. It is argued that conservation of biodiversity and ecosystems and changes in economic activities must be made to ward off new diseases, and why cooperation between ministries is critical to restrict the decline of biological diversity in a megadiverse country like India.

Major zoonotic diseases of public health importance in Bangladesh

Zoonotic diseases cause repeated outbreaks in humans globally. The majority of emerging infections in humans are zoonotic. COVID‐19 is an ideal example of a recently identified emerging zoonotic disease, causing a global pandemic. Anthropogenic factors such as modernisation of agriculture and livestock farming, wildlife hunting, the destruction of wild animal habitats, mixing wild and domestic animals, wildlife trading, changing food habits and urbanisation could drive the emergence of zoonotic diseases in humans. Since 2001, Bangladesh has been reporting many emerging zoonotic disease outbreaks such as nipah, highly pathogenic avian influenza, pandemic H1N1, and COVID‐19. There are many other potential zoonotic pathogens such as Ebola, Middle East respiratory syndrome coronavirus, Kyasanur forest disease virus and Crimean–Congo haemorrhagic fever that may emerge in the future. However, we have a limited understanding of zoonotic diseases’ overall risk in humans and associated factors that drive the emergence of zoonotic pathogens. This narrative review summarised the major emerging, re‐emerging, neglected and other potential zoonotic diseases in Bangladesh and their associated risk factors. Nipah virus and Bacillus anthracis caused repeated outbreaks in humans. More than 300 human cases with Nipah virus infection were reported since the first outbreak in 2001. The highly pathogenic avian influenza virus (H5N1) caused more than 550 outbreaks in poultry, and eight human cases were reported so far since 2007. People of Bangladesh are frequently exposed to zoonotic pathogens due to close interaction with domestic and peri‐domestic animals. The rapidly changing intensified animal–human–ecosystem interfaces and risky practices increase the risk of zoonotic disease transmission. The narrative review's findings are useful to draw attention to the risk and emergence of zoonotic diseases to public health policymakers in Bangladesh and the application of one‐health approach to address this public health threat.

The Ecology of Nipah Virus in Bangladesh: A Nexus of Land-Use Change and Opportunistic Feeding Behavior in Bats

Nipah virus is a bat-borne paramyxovirus that produces yearly outbreaks of fatal encephalitis in Bangladesh. Understanding the ecological conditions that lead to spillover from bats to humans can assist in designing effective interventions. To investigate the current and historical processes that drive Nipah spillover in Bangladesh, we analyzed the relationship among spillover events and climatic conditions, the spatial distribution and size of Pteropus medius roosts, and patterns of land-use change in Bangladesh over the last 300 years. We found that 53% of annual variation in winter spillovers is explained by winter temperature, which may affect bat behavior, physiology, and human risk behaviors. We infer from changes in forest cover that a progressive shift in bat roosting behavior occurred over hundreds of years, producing the current system where a majority of P. medius populations are small (median of 150 bats), occupy roost sites for 10 years or more, live in areas of high human population density, and opportunistically feed on cultivated food resources-conditions that promote viral spillover. Without interventions, continuing anthropogenic pressure on bat populations similar to what has occurred in Bangladesh could result in more regular spillovers of other bat viruses, including Hendra and Ebola viruses.

Nipah virus dynamics in bats and implications for spillover to humans

Nipah virus (NiV) is an emerging bat-borne zoonotic virus that causes near-annual outbreaks of fatal encephalitis in South Asia-one of the most populous regions on Earth. In Bangladesh, infection occurs when people drink date-palm sap contaminated with bat excreta. Outbreaks are sporadic, and the influence of viral dynamics in bats on their temporal and spatial distribution is poorly understood. We analyzed data on host ecology, molecular epidemiology, serological dynamics, and viral genetics to characterize spatiotemporal patterns of NiV dynamics in its wildlife reservoir, Pteropus medius bats, in Bangladesh. We found that NiV transmission occurred throughout the country and throughout the year. Model results indicated that local transmission dynamics were modulated by density-dependent transmission, acquired immunity that is lost over time, and recrudescence. Increased transmission followed multiyear periods of declining seroprevalence due to bat-population turnover and individual loss of humoral immunity. Individual bats had smaller host ranges than other Pteropus species (spp.), although movement data and the discovery of a Malaysia-clade NiV strain in eastern Bangladesh suggest connectivity with bats east of Bangladesh. These data suggest that discrete multiannual local epizootics in bat populations contribute to the sporadic nature of NiV outbreaks in South Asia. At the same time, the broad spatial and temporal extent of NiV transmission, including the recent outbreak in Kerala, India, highlights the continued risk of spillover to humans wherever they may interact with pteropid bats and the importance of limiting opportunities for spillover throughout Pteropus's range.

Possibility for reverse zoonotic transmission of SARS-CoV-2 to free-ranging wildlife: A case study of bats

The COVID-19 pandemic highlights the substantial public health, economic, and societal consequences of virus spillover from a wildlife reservoir. Widespread human transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) also presents a new set of challenges when considering viral spillover from people to naïve wildlife and other animal populations. The establishment of new wildlife reservoirs for SARS-CoV-2 would further complicate public health control measures and could lead to wildlife health and conservation impacts. Given the likely bat origin of SARS-CoV-2 and related beta-coronaviruses (β-CoVs), free-ranging bats are a key group of concern for spillover from humans back to wildlife. Here, we review the diversity and natural host range of β-CoVs in bats and examine the risk of humans inadvertently infecting free-ranging bats with SARS-CoV-2. Our review of the global distribution and host range of β-CoV evolutionary lineages suggests that 40+ species of temperate-zone North American bats could be immunologically naïve and susceptible to infection by SARS-CoV-2. We highlight an urgent need to proactively connect the wellbeing of human and wildlife health during the current pandemic and to implement new tools to continue wildlife research while avoiding potentially severe health and conservation impacts of SARS-CoV-2 "spilling back" into free-ranging bat populations.

Rousettus aegyptiacus Bats Do Not Support Productive Nipah Virus Replication

Nipah virus (NiV) is a bat-borne zoonotic pathogen that can cause severe respiratory distress and encephalitis upon spillover into humans. NiV is capable of infecting a broad range of hosts including humans, pigs, ferrets, dogs, cats, hamsters, and at least 2 genera of bats. Little is known about the biology of NiV in the bat reservoir. In this study, we evaluate the potential for the Egyptian fruit bat (EFB), Rousettus aegyptiacus, to serve as a model organism for studying NiV in bats. Our data suggest that NiV does not efficiently replicate in EFBs in vivo. Furthermore, we show no seroconversion against NiV glycoprotein and a lack of viral replication in primary and immortalized EFB-derived cell lines. Our data show that despite using a conserved target for viral entry, NiV replication is limited in some bat species. We conclude that EFBs are not an appropriate organism to model NiV infection or transmission in bats.

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.

Ecological interventions to prevent and manage zoonotic pathogen spillover

Spillover of a pathogen from a wildlife reservoir into a human or livestock host requires the pathogen to overcome a hierarchical series of barriers. Interventions aimed at one or more of these barriers may be able to prevent the occurrence of spillover. Here, we demonstrate how interventions that target the ecological context in which spillover occurs (i.e. ecological interventions) can complement conventional approaches like vaccination, treatment, disinfection and chemical control. Accelerating spillover owing to environmental change requires effective, affordable, durable and scalable solutions that fully harness the complex processes involved in cross-species pathogen spillover.

This article is part of the theme issue ‘Dynamic and integrative approaches to understanding pathogen spillover’.

Hospital-based zoonotic disease surveillance in Bangladesh: design, field data and difficulties

Early detection of zoonotic diseases allows for the implementation of early response measures, reducing loss of human life and economic disruption. We implemented a surveillance system in hospitals in Bangladesh to screen acutely ill hospitalized patients with severe respiratory infection and meningoencephalitis for zoonotic exposures. Patients were screened for the risk of zoonotic exposures with five questions covering vocational exposures, sick domestic animal and wild animal contact, and date palm sap consumption in the three weeks preceding illness onset. Patients giving at least one positive response were considered a potential zoonotic exposure. From September 2013 to March 2017, a total of 11 429 hospitalized patients across 14 participating hospitals were screened for exposures. Overall, 2% of patients reported a potential zoonotic exposure in the three-week period prior to becoming ill. Sixteen per cent of hospitalized patients with reported exposures died. After routine surveillance diagnostic testing, 88% of patients admitted to the hospital after a potential zoonotic exposure did not have a laboratory diagnosed aetiology for their illness. Hospital-based surveillance systems such as the Bangladeshi example presented here could play an important future role in the early detection of zoonotic spillover diseases. This article is part of the theme issue 'Dynamic and integrative approaches to understanding pathogen spillover'.

Characterization of the Spatial and Temporal Distribution of Nipah Virus Spillover Events in Bangladesh, 2007-2013

Nipah virus is a zoonotic virus harbored by bats and lethal to humans. Bat-to-human spillovers occur every winter in Bangladesh. However, there is significant heterogeneity in the number of spillovers detected by district and year that remains unexplained. We analyzed data from all 57 spillovers during 2007-2013 and found that temperature differences explained 36% of the year-to-year variation in the total number of spillovers each winter and that distance to surveillance hospitals explained 45% of spatial heterogeneity. Interventions to prevent human infections may be most important during colder winters. Further work is needed to understand how dynamics of bat infections explains spillover risk.

Nipah virus: epidemiology, pathology, immunobiology and advances in diagnosis, vaccine designing and control strategies - a comprehensive review

Nipah (Nee-pa) viral disease is a zoonotic infection caused by Nipah virus (NiV), a paramyxovirus belonging to the genus Henipavirus of the family Paramyxoviridae. It is a biosafety level-4 pathogen, which is transmitted by specific types of fruit bats, mainly Pteropus spp. which are natural reservoir host. The disease was reported for the first time from the Kampung Sungai Nipah village of Malaysia in 1998. Human-to-human transmission also occurs. Outbreaks have been reported also from other countries in South and Southeast Asia. Phylogenetic analysis affirmed the circulation of two major clades of NiV as based on currently available complete N and G gene sequences. NiV isolates from Malaysia and Cambodia clustered together in NiV-MY clade, whereas isolates from Bangladesh and India clusterered within NiV-BD clade. NiV isolates from Thailand harboured mixed population of sequences. In humans, the virus is responsible for causing rapidly progressing severe illness which might be characterized by severe respiratory illness and/or deadly encephalitis. In pigs below six months of age, respiratory illness along with nervous symptoms may develop. Different types of enzyme-linked immunosorbent assays along with molecular methods based on polymerase chain reaction have been developed for diagnostic purposes. Due to the expensive nature of the antibody drugs, identification of broad-spectrum antivirals is essential along with focusing on small interfering RNAs (siRNAs). High pathogenicity of NiV in humans, and lack of vaccines or therapeutics to counter this disease have attracted attention of researchers worldwide for developing effective NiV vaccine and treatment regimens.

Nipah virus: A review on epidemiological characteristics and outbreaks to inform public health decision making

The objectives of this review were to understand the epidemiology and outbreak of NiV infection and to discuss the preventive and control measures across different regions. We searched PubMed and Scopus for relevant articles from January 1999 to July 2018 and identified 927 articles which were screened for titles, abstracts and full texts by two review authors independently. The screening process resulted in 44 articles which were used to extract relevant information. Information on epidemiology of NiV, outbreaks in Malaysia, Singapore, Bangladesh, India and Philippines, including diagnosis, prevention, treatment, vaccines, control, surveillance and economic burden due to NiV were discussed. Interdisciplinary and multi sectoral approach is vital in preventing the emergence of NiV. It is necessary to undertake rigorous research for developing vaccines and medicines to prevent and treat NiV.

Nipah virus infection: A review

Nipah virus (NiV) is an emerging bat-borne pathogen. It was first identified 20 years ago in Malaysia and has since caused outbreaks in other parts of South and Southeast Asia. It causes severe neurological and respiratory disease which is highly lethal. It is highly infectious and spreads in the community through infected animals or other infected people. Different strains of the virus show differing clinical and epidemiological features. Rapid diagnosis and implementation of infection control measures are essential to contain outbreaks. A number of serological and molecular diagnostic techniques have been developed for diagnosis and surveillance. Difficulties in diagnosis and management arise when a new area is affected. The high mortality associated with infection and the possibility of spread to new areas has underscored the need for effective management and control. However, no effective treatment or prophylaxis is readily available, though several approaches show promise. Given the common chains of transmission from bats to humans, a One Health approach is necessary for the prevention and control of NiV infection.

Viruses Associated With Foodborne Infections

Foodborne pathogens cause acute and chronic health outcomes of very different durations, severity and mortality, resulting in high costs and burdens to society. The issues of food safety and food poisoning are being increasingly emphasised, particularly in developed countries. Infection/contamination with many agents i.e., bacterial, parasitic and viral entities can result in foodborne illness. This article will focus mainly on viral agents of infection.

A range of different viruses can cause food poisoning/foodborne infection, and infection can result in a myriad of symptoms, ranging from mild, acute disease to chronic, debilitating disease and even death. Due to the inherent differences between bacteria and viruses, namely the fact that viruses do not replicate in food, while bacteria do, viruses are frequently difficult to detect. This is compounded by the fact that many of the viruses associated with enteric disease do not replicate in cell culture. These factors can lead to a lag between reporting, detection and analysis of foodborne viruses versus bacterial agents. Despite these constraints, it is now evident that there are both well-established and emerging viruses implicated in foodborne infections, and the role of molecular detection and characterisation is becoming increasingly important.

Phylogeography, Transmission, and Viral Proteins of Nipah Virus

Nipah virus (NiV), a zoonotic paramyxovirus belonging to the genus Henipavirus, is classified as a Biosafety Level-4 pathogen based on its high pathogenicity in humans and the lack of available vaccines or therapeutics. Since its initial emergence in 1998 in Malaysia, this virus has become a great threat to domestic animals and humans. Sporadic outbreaks and person-to-person transmission over the past two decades have resulted in hundreds of human fatalities. Epidemiological surveys have shown that NiV is distributed in Asia, Africa, and the South Pacific Ocean, and is transmitted by its natural reservoir, Pteropid bats. Numerous efforts have been made to analyze viral protein function and structure to develop feasible strategies for drug design. Increasing surveillance and preventative measures for the viral infectious disease are urgently needed.

Changing resource landscapes and spillover of henipaviruses

Old World fruit bats (Chiroptera: Pteropodidae) provide critical pollination and seed dispersal services to forest ecosystems across Africa, Asia, and Australia. In each of these regions, pteropodids have been identified as natural reservoir hosts for henipaviruses. The genus Henipavirus includes Hendra virus and Nipah virus, which regularly spill over from bats to domestic animals and humans in Australia and Asia, and a suite of largely uncharacterized African henipaviruses. Rapid change in fruit bat habitat and associated shifts in their ecology and behavior are well documented, with evidence suggesting that altered diet, roosting habitat, and movement behaviors are increasing spillover risk of bat-borne viruses. We review the ways that changing resource landscapes affect the processes that culminate in cross-species transmission of henipaviruses, from reservoir host density and distribution to within-host immunity and recipient host exposure. We evaluate existing evidence and highlight gaps in knowledge that are limiting our understanding of the ecological drivers of henipavirus spillover. When considering spillover in the context of land-use change, we emphasize that it is especially important to disentangle the effects of habitat loss and resource provisioning on these processes, and to jointly consider changes in resource abundance, quality, and composition.

Mapping Disease Transmission Risk of Nipah Virus in South and Southeast Asia

Since 1998, Nipah virus (NiV) (genus: Henipavirus; family: Paramyxoviridae), an often-fatal and highly virulent zoonotic pathogen, has caused sporadic outbreak events. Fruit bats from the genus Pteropus are the wildlife reservoirs and have a broad distribution throughout South and Southeast Asia, and East Africa. Understanding the disease biogeography of NiV is critical to comprehending the potential geographic distribution of this dangerous zoonosis. This study implemented the R packages ENMeval and BIOMOD2 as a means of modeling regional disease transmission risk and additionally measured niche similarity between the reservoir Pteropus and the ecological characteristics of outbreak localities with the Schoener's D index and I statistic. Results indicate a relatively high degree of niche overlap between models in geographic and environmental space (D statistic, 0.64; and I statistic, 0.89), and a potential geographic distribution encompassing 19% (2,963,178 km²) of South and Southeast Asia. This study should contribute to current and future efforts to understand the critical ecological contributors and geography of NiV. Furthermore, this study can be used as a geospatial guide to identify areas of high disease transmission risk and to inform national public health surveillance programs.

Convergence of Humans, Bats, Trees, and Culture in Nipah Virus Transmission, Bangladesh

Preventing emergence of new zoonotic viruses depends on understanding determinants for human risk. Nipah virus (NiV) is a lethal zoonotic pathogen that has spilled over from bats into human populations, with limited person-to-person transmission. We examined ecologic and human behavioral drivers of geographic variation for risk of NiV infection in Bangladesh. We visited 60 villages during 2011–2013 where cases of infection with NiV were identified and 147 control villages. We compared case villages with control villages for most likely drivers for risk of infection, including number of bats, persons, and date palm sap trees, and human date palm sap consumption behavior. Case villages were similar to control villages in many ways, including number of bats, persons, and date palm sap trees, but had a higher proportion of households in which someone drank sap. Reducing human consumption of sap could reduce virus transmission and risk for emergence of a more highly transmissible NiV strain.

A VLP-based vaccine provides complete protection against Nipah virus challenge following multiple-dose or single-dose vaccination schedules in a hamster model

Nipah virus is a highly lethal zoonotic paramyxovirus that was first recognized in Malaysia during an outbreak in 1998. During this outbreak, Nipah virus infection caused a severe febrile neurological disease in humans who worked in close contact with infected pigs. The case fatality rate in humans was approximately 40%. Since 2001, NiV has re-emerged in Bangladesh and India where fruit bats (Pteropus spp.) have been identified as the principal reservoir of the virus. Transmission to humans is considered to be bat-to-human via food contaminated with bat saliva, or consumption of contaminated raw date palm sap, although human-to-human transmission of Nipah virus has also been documented. To date, there are no approved prophylactic options or treatment for NiV infection. In this study, we produced mammalian cell-derived native Nipah virus-like particles composed of Nipah virus G, F and M proteins for use as a novel Nipah virus vaccine. Previous studies demonstrated that the virus-like particles were structurally similar to authentic virus, functionally assembled and immunoreactive. In the studies reported here, purified Nipah virus-like particles were utilized either alone or with adjuvant to vaccinate golden Syrian hamsters with either three-dose or one-dose vaccination regimens followed by virus challenge. These studies found that Nipah virus-like particle immunization of hamsters induced significant neutralizing antibody titers and provided complete protection to all vaccinated animals following either single or three-dose vaccine schedules. These studies prove the feasibility of a virus-like particle-based vaccine for protection against Nipah virus infection.

Understanding the interaction between henipaviruses and their natural host, fruit bats: Paving the way toward control of highly lethal infection in humans

Hendra virus and Nipah virus (NiV) are highly pathogenic zoonotic paramyxoviruses, from henipavirus genus, that have emerged in late 1990s in Australia and South-East Asia, respectively. Since their initial identification, numerous outbreaks have been reported, affecting both domestic animals and humans, and multiple rounds of person-to-person NiV transmission were observed. Widely distributed fruit bats from Pteropodidae family were found to be henipavirus natural reservoir. Numerous studies have reported henipavirus seropositivity in pteropid bats, including bats in Africa, thus expanding notably the geographic distribution of these viruses. Interestingly, henipavirus infection in bats seems to be asymptomatic, in contrast to severe disease induced in numerous other mammals. Unique among the mammals by their ability to fly, these intriguing animals are natural reservoir for many other emerging and remerging viruses highly pathogenic for humans. This feature, combined with absence of clinical symptoms, has attracted the interest of scientific community to virus-bat interactions. Therefore, several bat genomes were sequenced and particularities of the bat immune system have been intensively analyzed during the last decade to understand their coexistence with viruses in the absence of disease. The peculiarities in inflammasome activation, a constitutive expression of interferon alpha, and some differences in adaptive immunity have been recently reported in fruit bats. Studies on virus-bat interactions have thus emerged as an exciting novel area of research that should shed new light on the mechanisms that regulate viral infection and may allow development of novel therapeutic approaches to control this highly lethal emerging infectious disease in humans.

Pathogenic Differences between Nipah Virus Bangladesh and Malaysia Strains in Primates: Implications for Antibody Therapy

Nipah virus (NiV) is a paramyxovirus that causes severe disease in humans and animals. There are two distinct strains of NiV, Malaysia (NiV_M) and Bangladesh (NiV_B). Differences in transmission patterns and mortality rates suggest that NiV_B may be more pathogenic than NiV_M. To investigate pathogenic differences between strains, 4 African green monkeys (AGM) were exposed to NiV_M and 4 AGMs were exposed to NiV_B. While NiV_B was uniformly lethal, only 50% of NiV_M-infected animals succumbed to infection. Histopathology of lungs and spleens from NiV_B-infected AGMs was significantly more severe than NiV_M-infected animals. Importantly, a second study utilizing 11 AGMs showed that the therapeutic window for human monoclonal antibody m102.4, previously shown to rescue AGMs from NiV_M infection, was much shorter in NiV_B-infected AGMs. Together, these data show that NiV_B is more pathogenic in AGMs under identical experimental conditions and suggests that postexposure treatments may need to be NiV strain specific for optimal efficacy.

Peri-exposure protection against Nipah virus disease using a single-dose recombinant vesicular stomatitis virus-based vaccine

Nipah virus is a zoonotic paramyxovirus that causes severe disease in humans and animals. Due to almost yearly outbreaks in Bangladesh, and a large outbreak in Malaysia that lead to the shutdown of swine export, Nipah virus is both a threat to public health and the economy. Infection is associated with respiratory distress, encephalitis and human-to-human transmission, resulting in high case fatality rates during outbreaks. This study aims to address the amount of time needed until protection from a recombinant vesicular stomatitis virus-based vaccine candidate expressing the Nipah virus glycoprotein (G), which we have previously shown to protect hamsters and non-human primates when administered 28 days before challenge. We found that a single-dose vaccination, when administered 1 day before challenge, reduced viral load, limited pathology and fully protected hamsters from Nipah virus infection. The vaccine was even partially protective when administered at early time points following challenge with Nipah virus. These data indicate that a single administration of this vaccine to high-risk individuals, such as family members and health-care workers of infected patients, could be protective and useful for reducing human-to-human transmission and curbing an outbreak.

Inhibition of the host antiviral response by Nipah virus: current understanding and future perspectives

Nipah virus (NiV) is a lethal paramyxovirus that has recently emerged as a human pathogen capable of causing acute respiratory disease and encephalitis. Like many viral pathogens, NiV has developed multiple means of antagonizing the host antiviral response. The viral proteins responsible for this antiviral inhibition are encoded in the NiV P gene and include the P, V, W and C proteins, which contain various unique and overlapping roles. This review examines the current data on inhibition of the host antiviral response for each of these proteins gathered from viral protein expression systems, in vitro data using recombinant NiV mutants and from in vivo studies using recombinant NiV mutants, as well as a future perspective regarding the direction of the field.

Nipah Virus Transmission from Bats to Humans Associated with Drinking Traditional Liquor Made from Date Palm Sap, Bangladesh, 2011-2014

Nipah virus (NiV) is a paramyxovirus, and Pteropus spp. bats are the natural reservoir. From December 2010 through March 2014, hospital-based encephalitis surveillance in Bangladesh identified 18 clusters of NiV infection. The source of infection for case-patients in 3 clusters in 2 districts was unknown. A team of epidemiologists and anthropologists investigated these 3 clusters comprising 14 case-patients, 8 of whom died. Among the 14 case-patients, 8 drank fermented date palm sap (tari) regularly before their illness, and 6 provided care to a person infected with NiV. The process of preparing date palm trees for tari production was similar to the process of collecting date palm sap for fresh consumption. Bat excreta was reportedly found inside pots used to make tari. These findings suggest that drinking tari is a potential pathway of NiV transmission. Interventions that prevent bat access to date palm sap might prevent tari-associated NiV infection.

The Role of Bats as Reservoir Hosts of Emerging Neuroviruses

Recent studies have clearly shown that bats are the reservoir hosts of a wide diversity of novel viruses with representatives from most of the known animal virus families. In many respects bats make ideal reservoir hosts for viruses: they are the only mammals that fly, thus assisting in virus dispersal; they roost in large numbers, thus aiding transmission cycles; some bats hibernate over winter, thus providing a mechanism for viruses to persist between seasons; and genetic factors may play a role in the ability of bats to host viruses without resulting in clinical disease. Within the broad diversity of viruses found in bats are some important neurological pathogens, including rabies and other lyssaviruses, and Hendra and Nipah viruses, two recently described viruses that have been placed in a new genus, Henipaviruses in the family Paramyxoviridae. In addition, bats can also act as alternative hosts for the flaviviruses Japanese encephalitis and St Louis encephalitis viruses, two important mosquito-borne encephalitogenic viruses, and bats can assist in the dispersal and over-wintering of these viruses. Bats are also the reservoir hosts of progenitors of SARS and MERS coronaviruses, although other animals act as spillover hosts. This chapter presents the physiological and ecological factors affecting the ability of bats to act as reservoirs of neurotropic viruses, and describes the major transmission cycles leading to human infection.

Raw Sap Consumption Habits and Its Association with Knowledge of Nipah Virus in Two Endemic Districts in Bangladesh

Human Nipah virus (NiV) infection in Bangladesh is a fatal disease that can be transmitted from bats to humans who drink contaminated raw date palm sap collected overnight during the cold season. Our study aimed to understand date palm sap consumption habits of rural residents and factors associated with consumption. In November-December 2012 the field team interviewed adult respondents from randomly selected villages from Rajbari and Kushtia Districts in Bangladesh. We calculated the proportion of people who consumed raw sap and had heard about a disease from raw sap consumption. We assessed the factors associated with raw sap consumption by calculating prevalence ratios (PR) adjusted for village level clustering effects. Among the 1,777 respondents interviewed, half (50%) reported drinking raw sap during the previous sap collection season and 37% consumed raw sap at least once per month. Few respondents (5%) heard about NiV. Thirty-seven percent of respondents reported hearing about a disease transmitted through raw sap consumption, inclusive of a 10% who related it with milder illness like diarrhea, vomiting or indigestion rather than NiV. Respondents who harvested date palm trees in their household were more likely to drink sap than those who did not own date palm trees (79% vs. 65% PR 1.2, 95% CI 1.1–1.3, p<0.001). When sap was available, respondents who heard about a disease from raw sap consumption were just as likely to drink it as those who did not hear about a disease (69% vs. 67%, PR 1.0, 95% CI 0.9–1.1, p = 0.512). Respondents’ knowledge of NiV was low. They might not have properly understood the risk of NiV, and were likely to drink sap when it was available. Implementing strategies to increase awareness about the risks of NiV and protect sap from bats might reduce the risk of NiV transmission.

Exposure-based screening for Nipah virus encephalitis, Bangladesh

We measured the performance of exposure screening questions to identify Nipah virus encephalitis in hospitalized encephalitis patients during the 2012–13 Nipah virus season in Bangladesh. The sensitivity (93%), specificity (82%), positive predictive value (37%), and negative predictive value (99%) results suggested that screening questions could more quickly identify persons with Nipah virus encephalitis.

[Bats and Viruses: complex relationships]

With more than 1 200 species, bats and flying foxes (Order Chiroptera) constitute the most important and diverse order of Mammals after Rodents. Many species of bats are insectivorous while others are frugivorous and few of them are hematophagous. Some of these animals fly during the night, others are crepuscular or diurnal. Some fly long distances during seasonal migrations. Many species are colonial cave-dwelling, living in a rather small home range while others are relatively solitary. However, in spite of the importance of bats for terrestrial biotic communities and ecosystem ecology, the diversity in their biology and lifestyles remain poorly known and underappreciated. More than sixty viruses have been detected or isolated in bats; these animals are therefore involved in the natural cycles of many of them. This is the case, for instance, of rabies virus and other Lyssavirus (Family Rhabdoviridae), Nipah and Hendra viruses (Paramyxoviridae), Ebola and Marburg viruses (Filoviridae), SARS-CoV and MERS-CoV (Coronaviridae). For these zoonotic viruses, a number of bat species are considered as important reservoir hosts, efficient disseminators or even directly responsible of the transmission. Some of these bat-borne viruses cause highly pathogenic diseases while others are of potential significance for humans and domestic or wild animals; so, bats are an important risk in human and animal public health. Moreover, some groups of viruses developed through different phylogenetic mechanisms of coevolution between viruses and bats. The fact that most of these viral infections are asymptomatic in bats has been observed since a long time but the mechanisms of the viral persistence are not clearly understood. The various bioecology of the different bat populations allows exchange of virus between migrating and non-migrating conspecific species. For a better understanding of the role of bats in the circulation of these viral zoonoses, epidemiologists must pay attention to some of their biologic properties which are not fully documented, like their extreme longevity, their diet, the population size and the particular densities observed in species with crowded roosting behavior, the population structure and migrations, the hibernation permitting overwintering of viruses, their particular innate and acquired immune response, probably related at least partially to their ability to fly, allowing persistent virus infections and preventing immunopathological consequences, etc. It is also necessary to get a better knowledge of the interactions between bats and ecologic changes induced by man and to attentively follow bat populations and their viruses through surveillance networks involving human and veterinary physicians, specialists of wild fauna, ecologists, etc. in order to understand the mechanisms of disease emergence, to try to foresee and, perhaps, to prevent viral emergences beforehand. Finally, a more fundamental research about immune mechanisms developed in viral infections is essential to reveal the reasons why Chiroptera are so efficient reservoir hosts. Clearly, a great deal of additional work is needed to document the roles of bats in the natural history of viruses.

Evolving epidemiology of Nipah virus infection in Bangladesh: evidence from outbreaks during 2010-2011

Drinking raw date palm sap is the primary route of Nipah virus (NiV) transmission from bats to people in Bangladesh; subsequent person-to-person transmission is common. During December 2010 to March 2011, we investigated NiV epidemiology by interviewing cases using structured questionnaires, in-depth interviews, and group discussions to collect clinical and exposure histories. We conducted a case-control study to identify risk factors for transmission. We identified 43 cases; 23 were laboratory-confirmed and 20 probable. Thirty-eight (88%) cases died. Drinking raw date palm sap and contact with an infected person were major risk factors; one healthcare worker was infected and for another case transmission apparently occurred through contact with a corpse. In absence of these risk factors, apparent routes of transmission included drinking fermented date palm sap. For the first time, a case was detected in eastern Bangladesh. Identification of new epidemiological characteristics emphasizes the importance of continued NiV surveillance and case investigation.

Animal models of disease shed light on Nipah virus pathogenesis and transmission

Nipah virus is an emerging virus infection that causes yearly disease outbreaks with high case fatality rates in Bangladesh. Nipah virus causes encephalitis and systemic vasculitis, sometimes in combination with respiratory disease. Pteropus species fruit bats are the natural reservoir of Nipah virus and zoonotic transmission can occur directly or via an intermediate host; human-to-human transmission occurs regularly. In this review we discuss the current state of knowledge on the pathogenesis and transmission of Nipah virus, focusing on dissemination of the virus through its host, known determinants of pathogenicity and routes of zoonotic and human-to-human transmission. Since data from human cases are sparse, this knowledge is largely based on the results of studies performed in animal models that recapitulate Nipah virus disease in humans.

Serological evidence of henipavirus exposure in cattle, goats and pigs in Bangladesh

Background

Nipah virus (NiV) is an emerging disease that causes severe encephalitis and respiratory illness in humans. Pigs were identified as an intermediate host for NiV transmission in Malaysia. In Bangladesh, NiV has caused recognized human outbreaks since 2001 and three outbreak investigations identified an epidemiological association between close contact with sick or dead animals and human illness.

Methodology

We examined cattle and goats reared around Pteropus bat roosts in human NiV outbreak areas. We also tested pig sera collected under another study focused on Japanese encephalitis.

Principal Findings

We detected antibodies against NiV glycoprotein in 26 (6.5%) cattle, 17 (4.3%) goats and 138 (44.2%) pigs by a Luminex-based multiplexed microsphere assay; however, these antibodies did not neutralize NiV. Cattle and goats with NiVsG antibodies were more likely to have a history of feeding on fruits partially eaten by bats or birds (PR = 3.1, 95% CI 1.6–5.7) and drinking palmyra palm juice (PR = 3.9, 95% CI 1.5–10.2).

Conclusions

This difference in test results may be due to the exposure of animals to one or more novel viruses with antigenic similarity to NiV. Further research may identify a novel organism of public health importance.

Nipah virus (NiV), is an emerging disease that causes severe encephalitis and respiratory illness in humans. Pigs were identified as an intermediate host for NiV transmission in Malaysia, and in Bangladesh three NiV outbreak investigations since 2001 identified an epidemiological association between close contact with sick or dead animals and human illness. We collected samples from cattle and goats reared around Pteropus bat roosts in human NiV outbreak areas in Bangladesh, and tested pig sera collected for a Japanese encephalitis study. We detected antibodies against NiV glycoprotein in 26 (6.5%) cattle, 17 (4.3%) goats and 138 (44.2%) pigs by a Luminex-based multiplexed microsphere assay, but none were virus neutralizing. There may have been exposure of Luminex positive animals to one or more novel viruses with antigenic similarity to NiV. Further research may identify a novel organism of public health importance.

Attachment protein G of an African bat henipavirus is differentially restricted in chiropteran and nonchiropteran cells

Henipaviruses are associated with pteropodid reservoir hosts. The glycoproteins G and F of an African henipavirus (strain M74) have been reported to induce syncytium formation in kidney cells derived from a Hypsignathus monstrosus bat (HypNi/1.1) but not in nonchiropteran BHK-21 and Vero76 cells. Here, we show that syncytia are also induced in two other pteropodid cell lines from Hypsignathus monstrosus and Eidolon helvum bats upon coexpression of the M74 glycoproteins. The G protein was transported to the surface of transfected chiropteran cells, whereas surface expression in the nonchiropteran cells was detectable only in a fraction of cells. In contrast, the G protein of Nipah virus is transported efficiently to the surface of both chiropteran and nonchiropteran cells. Even in chiropteran cells, M74-G was predominantly expressed in the endoplasmic reticulum (ER), as indicated by colocalization with marker proteins. This result is consistent with the finding that all N-glycans of the M74-G proteins are of the mannose-rich type, as indicated by sensitivity to endo H treatment. These data indicate that the surface transport of M74-G is impaired in available cell culture systems, with larger amounts of viral glycoprotein present on chiropteran cells than on nonchiropteran cells. The restricted surface expression of M74-G explains the reduced fusion activity of the glycoproteins of the African henipavirus. Our results suggest strategies for the isolation of infectious viruses, which is necessary to assess the risk of zoonotic virus transmission. Importance: Henipaviruses are highly pathogenic zoonotic viruses associated with pteropodid bat hosts. Whether the recently described African bat henipaviruses have a zoonotic potential as high as that of their Asian and Australian relatives is unknown. We show that surface expression of the attachment protein G of an African henipavirus, M74, is restricted in comparison to the G protein expression of the highly pathogenic Nipah virus. Transport to the cell surface is more restricted in nonchiropteran cells than it is in chiropteran cells, explaining the differential fusion activity of the M74 surface proteins in these cells. Our results imply that surface expression of viral glycoproteins may serve as a major marker to assess the zoonotic risk of emerging henipaviruses.