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

Optimal control analysis for the Nipah infection with constant and time-varying vaccination and treatment under real data application

In the last two decades, Nipah virus (NiV) has emerged as a significant paramyxovirus transmitted by bats, causing severe respiratory illness and encephalitis in humans. NiV has been included in the World Health Organization's Blueprint list of priority pathogens due its potential for human-to-human transmission and zoonotic characteristics. In this paper, a mathematical model is formulated to analyze the dynamics and optimal control of NiV. In formulation of the model we consider two modes of transmission: human-to-human and food-borne. Further, the impact of contact with an infected corpse as a potential route for virus transmission is also consider in the model. The analysis identifies the model with constant controls has three equilibrium states: the NiV-free equilibrium, the infected flying foxes-free equilibrium, and the NiV-endemic equilibrium state. Furthermore, a theoretical analysis is conducted to presents the stability of the model equilibria. The model fitting to the reported cases in Bangladesh from 2001 to 2015, and the estimation of parameters are performed using the standard least squares technique. Sensitivity analysis of the model-embedded parameters is provided to set the optimal time-dependent controls for the disease eradication. The necessary optimality conditions are derived using Pontryagin's maximum principle. Finally, numerical simulation is performed to determine the most effective strategy for disease eradication and to confirm the theoretical results.

A systematic review on Nipah virus: global molecular epidemiology and medical countermeasures development

Nipah virus (NiV) is an emerging pathogen that causes encephalitis and a high mortality rate in infected subjects. This systematic review aimed to comprehensively analyze the global epidemiology and research advancements of NiV to identify the key knowledge gaps in the literature. Articles searched using literature databases, namely PubMed, Scopus, Web of Science, and Science Direct yielded 5,596 articles. After article screening, 97 articles were included in this systematic review, comprising 41 epidemiological studies and 56 research developments on NiV. The majority of the NiV epidemiological studies were conducted in Bangladesh, reflecting the country's significant burden of NiV outbreaks. The initial NiV outbreak was identified in Malaysia in 1998, with subsequent outbreaks reported in Bangladesh, India, and the Philippines. Transmission routes vary by country, primarily through pigs in Malaysia, consumption of date palm juice in Bangladesh, and human-to-human in India. However, the availability of NiV genome sequences remains limited, particularly from Malaysia and India. Mortality rates also vary according to the country, exceeding 70% in Bangladesh, India, and the Philippines, and less than 40% in Malaysia. Understanding these differences in mortality rate among countries is crucial for informing NiV epidemiology and enhancing outbreak prevention and management strategies. In terms of research developments, the majority of studies focused on vaccine development, followed by phylogenetic analysis and antiviral research. While many vaccines and antivirals have demonstrated complete protection in animal models, only two vaccines have progressed to clinical trials. Phylogenetic analyses have revealed distinct clades between NiV Malaysia, NiV Bangladesh, and NiV India, with proposals to classify NiV India as a separate strain from NiV Bangladesh. Taken together, comprehensive OneHealth approaches integrating disease surveillance and research are imperative for future NiV studies. Expanding the dataset of NiV genome sequences, particularly from Malaysia, Bangladesh, and India will be pivotal. These research efforts are essential for advancing our understanding of NiV pathogenicity and for developing robust diagnostic assays, vaccines and therapeutics necessary for effective preparedness and response to future NiV outbreaks.

Global and regional mortality statistics of nipah virus from 1994 to 2023: a comprehensive systematic review and meta-analysis

The mortality rate of Nipah virus (NiV) can vary in different regions, and its pattern across timelines has yet to be assessed. The primary objective is to perform a comparative analysis of mortality rates across different timelines and countries. Articles reporting NiV mortality from inception to November 2023 were analyzed in PubMed, Ovid Embase, Scopus, and Web of Science databases. A meta-analysis utilizing random-effects models determined the mortality rate secondary to NiV complications. The initial search strategy yielded 1213 records, of which 36 articles met the inclusion criteria, comprising 2736 NiV patients. The Global mortality rate of the Nipah virus in the 2014-2023 decade was 80.1% (CI: 68.7-88.1%), indicating a significant 24% increase compared to the preceding decade (2004-2013) with a mortality rate of 54.1% (CI: 35.5-71.6%). Among the countries analyzed for overall mortality from 1994-2023, India experienced the highest mortality rate at 82.7% (CI: 74.6-88.6%), followed by Bangladesh at 62.1% (CI: 45.6-76.2%), Philippines at 52.9% (CI: 30-74.5%), Malaysia at 28.9% (CI: 21.4-37.9%), and Singapore at 21% (CI: 8-45%). Subgroup analysis revealed that India consistently had the highest mortality rate for the past two decades (91.7% and 89.3%). The primary complication leading to mortality was encephalitis, accounting for 95% of cases. This systematic review and meta-analysis revealed a noteworthy surge in NiV mortality rates, particularly in the current decade (2014-2023). The escalation, with India reporting a concerning level of mortality of 89.3-91.7% in the past decades, signifies a pressing public health challenge.

Molecular determinants of cross-species transmission in emerging viral infections

SUMMARYSeveral examples of high-impact cross-species transmission of newly emerging or re-emerging bat-borne viruses, such as Sudan virus, Nipah virus, and severe acute respiratory syndrome coronavirus 2, have occurred in the past decades. Recent advancements in next-generation sequencing have strengthened ongoing efforts to catalog the global virome, in particular from the multitude of different bat species. However, functional characterization of these novel viruses and virus sequences is typically limited with regard to assessment of their cross-species potential. Our understanding of the intricate interplay between virus and host underlying successful cross-species transmission has focused on the basic mechanisms of entry and replication, as well as the importance of host innate immune responses. In this review, we discuss the various roles of the respective molecular mechanisms underlying cross-species transmission using different recent bat-borne viruses as examples. To delineate the crucial cellular and molecular steps underlying cross-species transmission, we propose a framework of overall characterization to improve our capacity to characterize viruses as benign, of interest, or of concern.

Forecasting the future of Fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in India using ecological niche model

The Fall armyworm, Spodoptera frugiperda is the most notorious invasive pest species on maize, recently reported in India. The continuous spread of Fall armyworms to new ecological niches raises global concern. The current study is the first in India to forecast the suitability of a habitat for S. frugiperda using a maximum entropy algorithm. Predictions were made based on an analysis of the relationship between 109 occurrence records of S. frugiperda and pertinent historical, current, and predicted climatic data for the study area. The model indicated that S. frugiperda could thrive in different habitats under the current environmental circumstances, particularly in the west and south Indian states like Maharashtra, Tamil Nadu, and Karnataka. The model predicted that areas with higher latitudes, particularly in Uttar Pradesh, Odisha, West Bengal, and some portions of Telangana, Rajasthan, Chhattisgarh, and Madhya Pradesh, as well as some tracts of northeastern states like Assam and Arunachal Pradesh, would have highly climate-suitable conditions for S. frugiperda to occur in the future. The average AUC value was 0.852, which indicates excellent accuracy of the prediction. A Jackknife test of variables indicated that isothermality with the highest gain value was determining the potential geographic distribution of S. frugiperda. Our results will be useful for serving as an early warning tool to guide decision-making and prevent further spread toward new areas in India.

NIPAH Virus Encephalitis: Unveiling the Epidemiology, Risk Factors, and Clinical Outcomes - A Systematic Review and Meta-Analysis

Objective

This study assessed Nipah virus (NiV) encephalitis epidemiology, clinical outcomes, and risk variables to inform treatment and prevention.

Methodology

In a PubMed systematic search, 929 citations were found. After screening and eligibility, 22 studies were included. This study obtained age, gender, geographic regions, diagnostic methods, data collection methods, and bias risk. The case fatality rate (CFR) and NiV infection risk variables were evaluated by meta-analysis.

Results

Southeast Asia, especially Bangladesh and Malaysia, had the most NiV cases. The major diagnostic method was blood and cerebrospinal fluid IgM and IgG antibody tests, and males predominated. Proxy respondents and matched controls were utilized for risk factor analyses when patients could not answer. The pooled CFR for NiV encephalitis was 61.0%, indicating severity. Risk factors included pigs, nighttime bats near homes, tree climbing, and male gender.

Conclusion

Southeast Asian public health is plagued by NiV encephalitis. The high CFR calls for better diagnosis, treatment, and prevention. NiV's multiple risk factors must be understood for targeted therapy. Future research should fill knowledge gaps and improve NiV infection prevention.

Pathogenicity and virulence of henipaviruses

Paramyxoviruses are a family of single-stranded negative-sense RNA viruses, many of which are responsible for a range of respiratory and neurological diseases in humans and animals. Among the most notable are the henipaviruses, which include the deadly Nipah (NiV) and Hendra (HeV) viruses, the causative agents of outbreaks of severe disease and high case fatality rates in humans and animals. NiV and HeV are maintained in fruit bat reservoirs primarily in the family Pteropus and spillover into humans directly or by an intermediate amplifying host such as swine or horses. Recently, non-chiropteran associated Langya (LayV), Gamak (GAKV), and Mojiang (MojV) viruses have been discovered with confirmed or suspected ability to cause disease in humans or animals. These viruses are less genetically related to HeV and NiV yet share many features with their better-known counterparts. Recent advances in surveillance of wild animal reservoir viruses have revealed a high number of henipaviral genome sequences distributed across most continents, and mammalian orders previously unknown to harbour henipaviruses. In this review, we summarize the current knowledge on the range of pathogenesis observed for the henipaviruses as well as their replication cycle, epidemiology, genomics, and host responses. We focus on the most pathogenic viruses, including NiV, HeV, LayV, and GAKV, as well as the experimentally non-pathogenic CedV. We also highlight the emerging threats posed by these and potentially other closely related viruses.

The genetic diversity of Nipah virus across spatial scales

Nipah virus (NiV), a highly lethal virus in humans, circulates silently in Pteropus bats throughout South and Southeast Asia. Difficulty in obtaining genomes from bats means we have a poor understanding of NiV diversity, including how many lineages circulate within a roost and the spread of NiV over increasing spatial scales. Here we develop phylogenetic approaches applied to the most comprehensive collection of genomes to date (N=257, 175 from bats, 73 from humans) from six countries over 22 years (1999-2020). In Bangladesh, where most human infections occur, we find evidence of increased spillover risk from one of the two co-circulating sublineages. We divide the four major NiV sublineages into 15 genetic clusters (emerged 20-44 years ago). Within any bat roost, there are an average of 2.4 co-circulating genetic clusters, rising to 5.5 clusters at areas of 1,500-2,000 km2. Using Approximate Bayesian Computation fit to a spatial signature of viral diversity, we estimate that each genetic cluster occupies an average area of 1.3 million km2 (95%CI: 0.6-2.3 million), with 14 clusters in an area of 100,000 km2 (95%CI: 6-24). In the few sites in Bangladesh and Cambodia where genomic surveillance has been concentrated, we estimate that most of the genetic clusters have been identified, but only ~15% of overall NiV diversity has been uncovered. Our findings are consistent with entrenched co-circulation of distinct lineages, even within individual roosts, coupled with slow migration over larger spatial scales.

Tackling a global epidemic threat: Nipah surveillance in Bangladesh, 2006-2021

Human Nipah virus (NiV) infection is an epidemic-prone disease and since the first recognized outbreak in Bangladesh in 2001, human infections have been detected almost every year. Due to its high case fatality rate and public health importance, a hospital-based Nipah sentinel surveillance was established in Bangladesh to promptly detect Nipah cases and respond to outbreaks at the earliest. The surveillance has been ongoing till present. The hospital-based sentinel surveillance was conducted at ten strategically chosen tertiary care hospitals distributed throughout Bangladesh. The surveillance staff ensured that routine screening, enrollment, data, and specimen collection from suspected Nipah cases were conducted daily. The specimens were then processed and transported to the reference laboratory of Institute of Epidemiology, Disease Control and Research (IEDCR) and icddr,b for confirmation of diagnosis through serology and molecular detection. From 2006 to 2021, through this hospital-based surveillance platform, 7,150 individuals were enrolled and tested for Nipah virus. Since 2001, 322 Nipah infections were identified in Bangladesh, 75% of whom were laboratory confirmed cases. Half of the reported cases were primary cases (162/322) having an established history of consuming raw date palm sap (DPS) or tari (fermented date palm sap) and 29% were infected through person-to-person transmission. Since the initiation of surveillance, 68% (218/322) of Nipah cases from Bangladesh have been identified from various parts of the country. Fever, vomiting, headache, fatigue, and increased salivation were the most common symptoms among enrolled Nipah patients. Till 2021, the overall case fatality rate of NiV infection in Bangladesh was 71%. This article emphasizes that the overall epidemiology of Nipah virus infection in Bangladesh has remained consistent throughout the years. This is the only systematic surveillance to detect human NiV infection globally. The findings from this surveillance have contributed to early detection of NiV cases in hospital settings, understanding of Nipah disease epidemiology, and have enabled timely public health interventions for prevention and containment of NiV infection. Although we still have much to learn regarding the transmission dynamics and risk factors of human NiV infection, surveillance has played a significant role in advancing our knowledge in this regard.

Establishment of a neutralization assay for Nipah virus using a high-titer pseudovirus system

OBJECTIVE

To construct a high-titer Nipah pseudovirus packaging system using the HIV lentivirus backbone vector and establish a safe neutralization assay for Nipah pseudovirus in biosafety level 2 facilities.

METHODS

Nipah virus (NiV) fusion protein (F) and glycoprotein (G) recombinant expression plasmids, psPAX2, and pLenti CMV Puro LUC (w168-1) were transiently transfected into 293T cells for 72 h for the generation of a NiV pseudovirus. The neutralization ability of Nipah virus F and G protein antibodies was assessed using the pseudovirus.

RESULTS

A NiV pseudovirus was constructed using 293T cells. The ideal mass ratio of plasmid psPAX2: w168-1: F: G for transfection was determined to be 4:4:1:1. The specificity of recombinant F and G protein expression was indicated by indirect immunofluorescence and western blotting. The pseudovirus particles showed obvious spikes under a transmission electron microscope. The NiV pseudovirus titer was 4.73 × 10⁵ median tissue culture infective dose per mL, and the pseudovirus could be effectively neutralized by polyclonal antibodies specifically targeting the F and G proteins respectively.

CONCLUSIONS

A NiV pseudovirus was successfully generated using HIV vector systems, and was used as a platform for a safe and reliable pseudovirus-based neutralizing assay that can be performed in biosafety level 2 facilities.

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.

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.

Detailed analysis of the pathologic hallmarks of Nipah virus (Malaysia) disease in the African green monkey infected by the intratracheal route

Disease associated with Nipah virus infection causes a devastating and often fatal spectrum of syndromes predominated by both respiratory and neurologic conditions. Additionally, neurologic sequelae may manifest months to years later after virus exposure or apparent recovery. In the two decades since this disease emerged, much work has been completed in an attempt to understand the pathogenesis and facilitate development of medical countermeasures. Here we provide detailed organ system-specific pathologic findings following exposure of four African green monkeys to 2.41×105 pfu of the Malaysian strain of Nipah virus. Our results further substantiate the African green monkey as a model of human Nipah virus disease, by demonstrating both the respiratory and neurologic components of disease. Additionally, we demonstrate that a chronic phase of disease exists in this model, that may provide an important opportunity to study the enigmatic late onset and relapse encephalitis as it is described in human disease.

Livestock and Risk Group 4 Pathogens: Researching Zoonotic Threats to Public Health and Agriculture in Maximum Containment

Maximum-containment laboratories are a unique and essential component of the bioeconomy of the United States. These facilities play a critical role in the national infrastructure, supporting research on a select set of especially dangerous pathogens, as well as novel, emerging diseases. Understanding the ecology, biology, and pathology at the human-animal interface of zoonotic spillover events is fundamental to efficient control and elimination of disease. The use of animals as human surrogate models or as target-host models in research is an integral part of unraveling the interrelated components involved in these dynamic systems. These models can prove vitally important in determining both viral- and host-factors associated with virus transmission, providing invaluable information that can be developed into better risk mitigation strategies. In this article, we focus on the use of livestock in maximum-containment, biosafety level-4 agriculture (BSL-4Ag) research involving zoonotic, risk group 4 pathogens and we provide an overview of historical associated research and contributions. Livestock are most commonly used as target-host models in high-consequence, maximum-containment research and are routinely used to establish data to assist in risk assessments. This article highlights the importance of animal use, insights gained, and how this type of research is essential for protecting animal health, food security, and the agriculture economy, as well as human public health in the face of emerging zoonotic pathogens. The utilization of animal models in high-consequence pathogen research and continued expansion to include available species of agricultural importance is essential to deciphering the ecology of emerging and re-emerging infectious diseases, as well as for emergency response and mitigation preparedness.

Drivers of zoonotic disease risk in the Indian subcontinent: A scoping review

Literature on potential anthropogenic drivers of zoonotic disease risk in the Indian subcontinent is sparse. We conducted a scoping review to identify primary sources, published 2000-2020, to clarify what research exists and on which areas future research should focus. We summarised findings thematically by disease. Of 80 sources included, 78 (98%) were original research articles and two were conference abstracts. Study designs and methods were not always clearly described, but 74 (93%) were quantitative (including one randomised trial), five (6%) were mixed-methods, and one was qualitative. Most sources reported research from India (39%) or Bangladesh (31%), followed by Pakistan (9%), Nepal (9%), Bhutan and Sri Lanka (6% each). Topically, most focused on rabies (18; 23%), Nipah virus (16; 20%) or leptospirosis (11; 14%), while 12 (15%) did not focus on a disease but instead on knowledge in communities. People generally did not seek post-exposure prophylaxis for rabies even when vaccination programmes were available and they understood that rabies was fatal, instead often relying on traditional medicines. Similarly, people did not take precautions to protect themselves from leptospirosis infection, even when they were aware of the link with rice cultivation. Nipah was correlated with presence of bats near human habitation. Official information on diseases, modes of transmission and prevention was lacking, or shared informally between friends, relatives, and neighbours. Behaviour did not correspond to disease knowledge. This review identifies various human behaviours which may drive zoonotic disease risk in the Indian subcontinent. Increasing community knowledge and awareness alone is unlikely to be sufficient to successfully change these behaviours. Further research, using interdisciplinary and participatory methods, would improve understanding of risks and risk perceptions and thus help in co-designing context-specific, relevant interventions.

A Brighton Collaboration standardized template with key considerations for a benefit/risk assessment for a soluble glycoprotein vaccine to prevent disease caused by Nipah or Hendra viruses

Auro Vaccines LLC has developed a protein vaccine to prevent disease from Nipah and Hendra virus infection that employs a recombinant soluble Hendra glycoprotein (HeV-sG) adjuvanted with aluminum phosphate. This vaccine is currently under clinical evaluation in a Phase 1 study. The Benefit-Risk Assessment of VAccines by TechnolOgy Working Group (BRAVATO; ex-V3SWG) has prepared a standardized template to describe the key considerations for the benefit-risk assessment of protein vaccines. This will help key stakeholders to assess potential safety issues and understand the benefit-risk of such a vaccine platform. The structured and standardized assessment provided by the template may also help contribute to improved public acceptance and communication of licensed protein vaccines.

Reinforcement learning-based decision support system for COVID-19

Globally, informed decision on the most effective set of restrictions for the containment of COVID-19 has been the subject of intense debates. There is a significant need for a structured dynamic framework to model and evaluate different intervention scenarios and how they perform under different national characteristics and constraints. This work proposes a novel optimal decision support framework capable of incorporating different interventions to minimize the impact of widely spread respiratory infectious pandemics, including the recent COVID-19, by taking into account the pandemic's characteristics, the healthcare system parameters, and the socio-economic aspects of the community. The theoretical framework underpinning this work involves the use of a reinforcement learning-based agent to derive constrained optimal policies for tuning a closed-loop control model of the disease transmission dynamics.

A single dose investigational subunit vaccine for human use against Nipah virus and Hendra virus

Nipah and Hendra viruses are highly pathogenic bat-borne paramyxoviruses recently included in the WHO Blueprint priority diseases list. A fully registered horse anti-Hendra virus subunit vaccine has been in use in Australia since 2012. Based on the same immunogen, the Hendra virus attachment glycoprotein ectodomain, a subunit vaccine formulation for use in people is now in a Phase I clinical trial. We report that a single dose vaccination regimen of this human vaccine formulation protects against otherwise lethal challenges of either Hendra or Nipah virus in a nonhuman primate model. The protection against the Nipah Bangladesh strain begins as soon as 7 days post immunization with low dose of 0.1 mg protein subunit. Our data suggest this human vaccine could be utilized as efficient emergency vaccine to disrupt potential spreading of Nipah disease in an outbreak setting.

Inference of Nipah virus evolution, 1999-2015

Despite near-annual human outbreaks of Nipah virus (NiV) disease in Bangladesh, typically due to individual spillover events from the local bat population, only twenty whole-genome NiV sequences exist from humans and ten from bats. NiV whole-genome sequences from annual outbreaks have been challenging to generate, primarily due to the low viral load in human throat swab and serum specimens. Here, we used targeted enrichment with custom NiV-specific probes and generated thirty-five additional unique full-length genomic sequences directly from human specimens and viral isolates. We inferred the temporal and geographic evolutionary history of NiV in Bangladesh and expanded a tool to visualize NiV spatio-temporal spread from a Bayesian continuous diffusion analysis. We observed that strains from Bangladesh segregated into two distinct clades that have intermingled geographically in Bangladesh over time and space. As these clades expanded geographically and temporally, we did not observe evidence for significant branch and site-specific selection, except for a single site in the Henipavirus L polymerase. However, the Bangladesh 1 and 2 clades are differentiated by mutations initially occurring in the polymerase, with additional mutations accumulating in the N, G, F, P, and L genes on external branches. Modeling the historic geographical and temporal spread demonstrates that while widespread, NiV does not exhibit significant genetic variation in Bangladesh. Thus, future public health measures should address whether NiV within in the bat population also exhibits comparable genetic variation, if zoonotic transmission results in a genetic bottleneck and if surveillance techniques are detecting only a subset of NiV.

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.

Stakeholder Perspective of Handling the Deceased during the Nipah Virus Outbreak in Kerala, South India, 2018

In any outbreak situation, a poor stakeholder response can impede the outbreak control and can have high economic and social cost. We conducted a qualitative study to understand stakeholder response in handling of the Nipah deceased persons during the outbreak of Nipah in Kerala, 2018. To understand the responses and to generate knowledge from the data, we used grounded theory approach for the study and conducted in-depth interviews and focus group discussion. Mixed public response and swift state response emerged as the main themes in our study. Under the "mixed public response," three categories emerged, including anxiety and fear, conflicting religious beliefs, and humanitarian concern. Under the "swift state response," the categories emerged were critical resources and robust guidance. A collective effort involving the administration, local and religious groups, and a culturally acceptable scientific protocol proved to be good examples of gaining social acceptance. Kerala puts forth a model of efficient community engagement and communication to gain public support and acceptance in a fatal disease outbreak.

Remdesivir (GS-5734) protects African green monkeys from Nipah virus challenge

Nipah virus is an emerging pathogen in the Paramyxoviridae family. Upon transmission of Nipah virus from its natural reservoir, Pteropus spp. fruit bats, to humans, it causes respiratory and neurological disease with a case-fatality rate about 70%. Human-to-human transmission has been observed during Nipah virus outbreaks in Bangladesh and India. A therapeutic treatment for Nipah virus disease is urgently needed. Here, we tested the efficacy of remdesivir (GS-5734), a broad-acting antiviral nucleotide prodrug, against Nipah virus Bangladesh genotype in African green monkeys. Animals were inoculated with a lethal dose of Nipah virus, and a once-daily intravenous remdesivir treatment was initiated 24 hours later and continued for 12 days. Mild respiratory signs were observed in two of four treated animals, whereas all control animals developed severe respiratory disease signs. In contrast to control animals, which all succumbed to the infection, all remsdesivir-treated animals survived the lethal challenge, indicating that remdesivir represents a promising antiviral treatment for Nipah virus infection.

An Intranasal Exposure Model of Lethal Nipah Virus Infection in African Green Monkeys

Due to the difficulty in conducting clinical trials for vaccines and treatments against Nipah virus (NiV), licensure will likely require animal models, most importantly non-human primates (NHPs). The NHP models of infection have primarily relied on intratracheal instillation or small particle aerosolization of NiV. However, neither of these routes adequately models natural mucosal exposure to NiV. To develop a more natural NHP model, we challenged African green monkeys with the Bangladesh strain of NiV by the intranasal route using the laryngeal mask airway (LMA) mucosal atomization device (MAD). LMA MAD exposure resulted in uniformly lethal disease that accurately reflected the human condition.

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.

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.

Case fatality rate and risk factors for Nipah virus encephalitis: A systematic review and meta-analysis

BACKGROUND

A wide range of Nipah virus (NiV) encephalitis case fatality rates (CFR) have been reported. Data on the involvement of several potential risk factors in Nipah virus transmission remain controversial. We performed a systematic review and meta-analysis to estimate the pooled CFR of NiV encephalitis and to assess the risk factors for NiV infection.

METHODS

Articles published up to the 27^thof November 2018 in MedLine, Embase and Web of knowledge databases were considered for this study. We included cross-sectional, cohort, and case-control studies that have reported NiV CFR and/or risk factors. Data were pooled with random-effects model. This review was registered in the PROSPERO, CRD42018116242.

FINDINGS

This global review included 22 citations (25 studies) including 2156, 1682, and 474 suspected, probable, and confirmed cases of NiV encephalitis, respectively. We determined a pooled CFR for NiV encephalitis at 61.0% (95% CI, 45.7-75.4; I² = 96.8%). Climbing trees (OR = 1.4; 95% CI; 1.0-1.9), male gender (OR = 1.5; 95% CI; 1.1-2.0), travel outside their own sub-district (OR = 2.0; 95% CI; 1.4-2.9), and exposure to date palm sap (DPS) (OR = 5.7; 95% CI; 3.8-8.6) or pigs (OR = 7.6; 95% CI; 1.2-45.4) were significantly associated with NiV infection.

CONCLUSION

Findings from this study suggest that NiV Encephalitis is associated with a high CFR and that male gender, travel outside their sub-district, climbing trees, and exposure to pigs and DPS are associated with an increased risk of NiV encephalitis.

Transmission of Nipah Virus - 14 Years of Investigations in Bangladesh

BACKGROUND

Nipah virus is a highly virulent zoonotic pathogen that can be transmitted between humans. Understanding the dynamics of person-to-person transmission is key to designing effective interventions.

METHODS

We used data from all Nipah virus cases identified during outbreak investigations in Bangladesh from April 2001 through April 2014 to investigate case-patient characteristics associated with onward transmission and factors associated with the risk of infection among patient contacts.

RESULTS

Of 248 Nipah virus cases identified, 82 were caused by person-to-person transmission, corresponding to a reproduction number (i.e., the average number of secondary cases per case patient) of 0.33 (95% confidence interval [CI], 0.19 to 0.59). The predicted reproduction number increased with the case patient's age and was highest among patients 45 years of age or older who had difficulty breathing (1.1; 95% CI, 0.4 to 3.2). Case patients who did not have difficulty breathing infected 0.05 times as many contacts (95% CI, 0.01 to 0.3) as other case patients did. Serologic testing of 1863 asymptomatic contacts revealed no infections. Spouses of case patients were more often infected (8 of 56 [14%]) than other close family members (7 of 547 [1.3%]) or other contacts (18 of 1996 [0.9%]). The risk of infection increased with increased duration of exposure of the contacts (adjusted odds ratio for exposure of >48 hours vs. ≤1 hour, 13; 95% CI, 2.6 to 62) and with exposure to body fluids (adjusted odds ratio, 4.3; 95% CI, 1.6 to 11).

CONCLUSIONS

Increasing age and respiratory symptoms were indicators of infectivity of Nipah virus. Interventions to control person-to-person transmission should aim to reduce exposure to body fluids. (Funded by the National Institutes of Health and others.).

Henipaviruses at the Interface Between Bats, Livestock and Human Population in Africa

Nipah virus (NiV) and Hendra virus (HeV) are closely related members within the genus Henipavirus, family Paramyxoviridae, for which fruit bats serve as the reservoir. The initial emergence of NiV infections in pigs and humans in Malaysia, and HeV infections in horses and humans in Australia, posed severe impacts on human and animal health, and continues threatening lives of humans and livestock within Southeast Asia and Australia. Recently, henipavirus-specific antibodies have also been detected in fruit bats in a number of sub-Saharan African countries and in Brazil, thereby considerably increasing the known geographic distribution of henipaviruses. Africa is progressively being recognized as a new high prevalence zone for henipaviruses, as deduced from serological and molecular evidence of past infections in Madagascar, Ghana, Republic of Congo, Gulf of Guinea, Zambia, Tanzania, Cameroon, and Nigeria lately. Serological data suggest henipavirus spillover from bats to livestock and human populations in Africa without reported clinical disease in any of these species. All virus isolation attempts have been abortive, highlighting the need for further investigations. The genome of the Ghanaian bat henipavirus designated Ghana virus (GhV), which was detected in a pteropid Eidolon helvum bat, is the only African henipavirus that has been completely sequenced limiting our current knowledge on the genetic diversity and pathogenesis of African henipaviruses. In this review, we summarize the available data on the circulation of henipaviruses in Africa, discuss potential sources for virus spillover, and highlight existing research gaps.

Aerosol exposure to intermediate size Nipah virus particles induces neurological disease in African green monkeys

Nipah virus (NiV) infection can lead to severe respiratory or neurological disease in humans. Transmission of NiV has been shown to occur through contact with virus contaminated fomites or consumption of contaminated food. Previous results using the African green monkey (AGM) model of NiV infection identified aspects of infection that, while similar to humans, don’t fully recapitulate disease. Previous studies also demonstrate near uniform lethality that is not consistent with human NiV infection. In these studies, aerosol exposure using an intermediate particle size (7μm) was used to mimic potential human exposure by facilitating virus deposition in the upper respiratory tract. Computed tomography evaluation found some animals developed pulmonary parenchymal disease including consolidations, ground-glass opacities, and reactive adenopathy. Despite the lack of neurological signs, magnetic resonance imaging identified distinct brain lesions in three animals, similar to those previously reported in NiV-infected patients. Immunological characterization of tissues collected at necropsy suggested a local pulmonary inflammatory response with increased levels of macrophages in the lung, but a limited neurologic response. These data provide the first clear evidence of neurological involvement in the AGM that recapitulates human disease. With the development of a disease model that is more representative of human disease, these data suggest that NiV infection in the AGM may be appropriate for evaluating therapeutic countermeasures directed at virus-induced neuropathogenesis.

The development of effective therapeutic approaches to the treatment of human diseases requires an understanding of the disease process induced by an infectious agent. Historically the development of medical countermeasures for highly pathogenic viruses required the use of a uniformly lethal animal model. While this approach is useful in some regards, it frequently does not provide a true indication of the disease process. In the work presented here, the approach was to use a virus exposure method that mimicked a potential route of human exposure and used a dose that might be more representative of one a human would receive. Using this method and advanced medical imaging techniques, we were able to demonstrate an extended disease course with mixed respiratory and neurological disease like that seen in humans. This study also found that the response to infection in the lungs was inflammatory and that the disease in the brain was limited despite clear evidence of lesions. These data support the development of animal models that mimic human disease and allow for the identification of potential therapeutic approaches that target the disease process rather than only the virus.

Nipah Virus Contamination of Hospital Surfaces during Outbreaks, Bangladesh, 2013-2014

Nipah virus (NiV) has been transmitted from patient to caregivers in Bangladesh presumably through oral secretions. We aimed to detect whether NiV-infected patients contaminate hospital surfaces with the virus. During December 2013–April 2014, we collected 1 swab sample from 5 surfaces near NiV-infected patients and tested surface and oral swab samples by real-time reverse transcription PCR for NiV RNA. We identified 16 Nipah patients; 12 cases were laboratory-confirmed and 4 probable. Of the 12 laboratory-confirmed cases, 10 showed NiV RNA in oral swab specimens. We obtained surface swab samples for 6 Nipah patients; 5 had evidence of NiV RNA on >1 surface: 4 patients contaminated towels, 3 bed sheets, and 1 the bed rail. Patients with NiV RNA in oral swab samples were significantly more likely than other Nipah patients to die. To reduce the risk for fomite transmission of NiV, infection control should target hospital surfaces.

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.

Transmission of henipaviruses

The genus Henipavirus has expanded rapidly in geographic range, number of species, and host range. Hendra and Nipah virus are two henipaviruses known to cause severe disease in humans with a high case-fatality rate. Pteropid spp. bats are the natural reservoir of Hendra and Nipah virus. From these bats, virus can be transmitted to an amplifying host, horses and pigs, and from these hosts to humans, or the virus can be transmitted directly to humans. Although the main route of shedding varies between host species, close contact is required for transmission in all hosts. Understanding the transmission routes of Hendra and Nipah virus in their respective hosts is essential for devising strategies to block zoonotic transmission.

Loss in lung volume and changes in the immune response demonstrate disease progression in African green monkeys infected by small-particle aerosol and intratracheal exposure to Nipah virus

Nipah virus (NiV) is a paramyxovirus (genus Henipavirus) that emerged in the late 1990s in Malaysia and has since been identified as the cause of sporadic outbreaks of severe febrile disease in Bangladesh and India. NiV infection is frequently associated with severe respiratory or neurological disease in infected humans with transmission to humans through inhalation, contact or consumption of NiV contaminated foods. In the work presented here, the development of disease was investigated in the African Green Monkey (AGM) model following intratracheal (IT) and, for the first time, small-particle aerosol administration of NiV. This study utilized computed tomography (CT) and magnetic resonance imaging (MRI) to temporally assess disease progression. The host immune response and changes in immune cell populations over the course of disease were also evaluated. This study found that IT and small-particle administration of NiV caused similar disease progression, but that IT inoculation induced significant congestion in the lungs while disease following small-particle aerosol inoculation was largely confined to the lower respiratory tract. Quantitative assessment of changes in lung volume found up to a 45% loss in IT inoculated animals. None of the subjects in this study developed overt neurological disease, a finding that was supported by MRI analysis. The development of neutralizing antibodies was not apparent over the 8–10 day course of disease, but changes in cytokine response in all animals and activated CD8+ T cell numbers suggest the onset of cell-mediated immunity. These studies demonstrate that IT and small-particle aerosol infection with NiV in the AGM model leads to a severe respiratory disease devoid of neurological indications. This work also suggests that extending the disease course or minimizing the impact of the respiratory component is critical to developing a model that has a neurological component and more accurately reflects the human condition.

Nipah virus (NiV) was identified in the late 1990s as the causative agent of severe respiratory and neurological disease in Malaysia and Bangladesh. The virus is transmitted by inhalation, contact or consumption of contaminated material. In this study, our objective was to characterize NiV-induced disease progression in the African Green Monkey model utilizing clinical imaging capabilities. In this work, we also provide the first temporal evaluation of the immune response to infection following NiV infection and the first characterization of disease following aerosol exposure. Here, we found that NiV infection following intratracheal and aerosol exposure lead to a severe respiratory disease and rapid disease course with no overt clinical evidence of neurological disease. Despite the rapid course of disease, changes in the cytokine response and peripheral immune cell populations suggest development of a cell-mediated immune response in the latter stage of disease. While the current model for evaluating NiV infection is useful for testing of medical countermeasures, further work is required to understand how this model can represent human disease.

Nipah virus: transmission of a zoonotic paramyxovirus

Nipah virus is a recently-recognised, zoonotic paramyxovirus that causes severe disease and high fatality rates in people. Outbreaks have occurred in Malaysia, Singapore, India and Bangladesh, and a putative Nipah virus was also recently associated with human disease in the Philippines. Worryingly, human-to-human transmission is common in Bangladesh, where outbreaks occur with near-annual frequency. Onward human transmission of Nipah virus in Bangladesh is associated with close contact with clinically-unwell patients or their infectious secretions. While Nipah virus isolates associated with outbreaks of human infection have not resulted in sustained transmission to date, specific exposures carry a high risk of person-to-person transmission, an observation which is supported by recent findings in animal models. Novel paramyxoviruses continue to emerge from wildlife hosts, and represent an ongoing threat to human health globally.

The Nature of Exposure Drives Transmission of Nipah Viruses from Malaysia and Bangladesh in Ferrets

Person-to-person transmission is a key feature of human Nipah virus outbreaks in Bangladesh. In contrast, in an outbreak of Nipah virus in Malaysia, people acquired infections from pigs. It is not known whether this important epidemiological difference is driven primarily by differences between NiV Bangladesh (NiV-BD) and Malaysia (NiV-MY) at a virus level, or by environmental or host factors. In a time course study, ferrets were oronasally exposed to equivalent doses of NiV-BD or NiV-MY. More rapid onset of productive infection and higher levels of virus replication in respiratory tract tissues were seen for NiV-BD compared to NiV-MY, corroborating our previous report of increased oral shedding of NiV-BD in ferrets and suggesting a contributory mechanism for increased NiV-BD transmission between people compared to NiV-MY. However, we recognize that transmission occurs within a social and environmental framework that may have an important and differentiating role in NiV transmission rates. With this in mind, ferret-to-ferret transmission of NiV-BD and NiV-MY was assessed under differing viral exposure conditions. Transmission was not identified for either virus when naïve ferrets were cohoused with experimentally-infected animals. In contrast, all naïve ferrets developed acute infection following assisted and direct exposure to oronasal fluid from animals that were shedding either NiV-BD or NiV-MY. Our findings for ferrets indicate that, although NiV-BD may be shed at higher levels than NiV-MY, transmission risk may be equivalently low under exposure conditions provided by cohabitation alone. In contrast, active transfer of infected bodily fluids consistently results in transmission, regardless of the virus strain. These observations suggest that the risk of NiV transmission is underpinned by social and environmental factors, and will have practical implications for managing transmission risk during outbreaks of human disease.

Increased Morbidity and Mortality in Domestic Animals Eating Dropped and Bitten Fruit in Bangladeshi Villages: Implications for Zoonotic Disease Transmission

We used data on feeding practices and domestic animal health gathered from 207 Bangladeshi villages to identify any association between grazing dropped fruit found on the ground or owners directly feeding bat- or bird-bitten fruit and animal health. We compared mortality and morbidity in domestic animals using a mixed effects model controlling for village clustering, herd size, and proxy measures of household wealth. Thirty percent of household heads reported that their animals grazed on dropped fruit and 20% reported that they actively fed bitten fruit to their domestic herds. Household heads allowing their cattle to graze on dropped fruit were more likely to report an illness within their herd (adjusted prevalence ratio 1.17, 95% CI 1.02-1.31). Household heads directly feeding goats bitten fruit were more likely to report illness (adjusted prevalence ratio 1.35, 95% CI 1.16-1.57) and deaths (adjusted prevalence ratio 1.64, 95% CI 1.13-2.4). Reporting of illnesses and deaths among goats rose as the frequency of feeding bitten fruit increased. One possible explanation for this finding is the transmission of bat pathogens to domestic animals via bitten fruit consumption.