Person-to-person transmission of Nipah virus in a Bangladeshi community

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.

Emerging and Reemerging Viral Diseases

An emerging infectious disease (EID) is defined as a disease caused by a pathogen that has not been observed previously within a population or geographic location. Viruses are a major cause of EIDs, particularly −ssRNA viruses. Many variables are involved in the emergence or reemergence of viruses. These can be classified into human factors, environmental/ecological factors, and viral factors and include urbanization, globalization, weather and climate change, and the genetic composition of the virus. The great majority of emerging viral diseases are zoonoses, notably transmitted by arthropods and nonhuman mammals. Flaviviruses include several notable vector-transmitted viruses, while rodents and bats are thought to be the natural reservoirs of arenaviruses and filoviruses, respectively. This chapter discusses several notable outbreaks of emerging and reemerging viruses, including the 2014–15 outbreak of Ebolavirus in West Africa.

Serological Evidence of Henipavirus among Horses and Pigs in Zaria and Environs in Kaduna State, Nigeria

Henipavirus is an emerging, zoonotic, and lethal RNA virus comprising Hendra virus (HeV) and Nipah virus (NiV), to which fruit bats are reservoir. Husbandry practices in Nigeria allow close contact between bat reservoir and animals susceptible to Henipavirus. This cross-sectional survey investigated antibodies reactive to Henipavirus sG antigen and associated risk factors in horses and pigs in Zaria, Nigeria. Using convenience sampling, 510 sera from horses (n=200) and pigs (n=310) were screened by an indirect Henipavirus enzyme-linked immunosorbent assay (ELISA) (CSIRO, Australia). Structured questionnaires were employed with questions on the demographics and management of the animals. Data were analysed using SPSS-17. 5. Seroprevalence was higher for horses managed intensively (21.1%); used for sports (25.5%); watered with pipe borne water (17.9%); fed commercial feed (22.3%); and fed in the pen (17.6%). Seroprevalence was higher for pigs managed intensively (58.1%); imported (69.5%); watered with pipe-borne water (31.3%); fed commercial feed (57.4%); fed in the pen (23.4%), and fed with feed prestored in a feed house (49.5%). Horses <5 years and pigs <6 months had higher seroprevalences of 18.1% and 21.3%, while the female horses and pigs had seroprevalences of 19.8% and 22.8%, respectively. Exotic horses and pigs revealed 25.5% and 55% and horses in Igabi and pigs in Giwa revealed 24.7% and 70.2% seroprevalence, respectively (P<0.05). There is a suggestive evidence of Henipavirus in horses and pigs in Zaria, Nigeria, with a huge public health implication. Local and exotic pigs and horses, pigs in Zaria and Sabon-Gari, and horses in Zaria, Sabon-Gari, and Kaduna North are associated with the seroprevalence of henipaviruses.

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.

Outbreak of henipavirus infection, Philippines, 2014

During 2014, henipavirus infection caused severe illness among humans and horses in southern Philippines; fatality rates among humans were high. Horse-to-human and human-to-human transmission occurred. The most likely source of horse infection was fruit bats. Ongoing surveillance is needed for rapid diagnosis, risk factor investigation, control measure implementation, and further virus characterization.

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.

Henipavirus Encephalitis: Recent Developments and Advances

The genus Henipavirus within the family Paramyxoviridae includes the Hendra virus (HeV) and Nipah virus (NiV) which were discovered in the 1990s in Australia and Malaysia, respectively, after emerging to cause severe and often fatal outbreaks in humans and animals. While HeV is confined to Australia, more recent NiV outbreaks have been reported in Bangladesh, India and the Philippines. The clinical manifestations of both henipaviruses in humans appear similar, with a predominance of an acute encephalitic syndrome. Likewise, the pathological features are similar and characterized by disseminated, multi-organ vasculopathy comprising endothelial infection/ulceration, vasculitis, vasculitis-induced thrombosis/occlusion, parenchymal ischemia/microinfarction, and parenchymal cell infection in the central nervous system (CNS), lung, kidney and other major organs. This unique dual pathogenetic mechanism of vasculitis-induced microinfarction and neuronal infection causes severe tissue damage in the CNS. Both viruses can also cause relapsing encephalitis months and years after the acute infection. Many animal models studied to date have largely confirmed the pathology of henipavirus infection, and provided the means to test new therapeutic agents and vaccines. As the bat is the natural host of henipaviruses and has worldwide distribution, spillover events into human populations are expected to occur in the future.

Zoonotic Viruses and Conservation of Bats

Many of the recently emerging highly virulent zoonotic diseases have a likely bat origin, for example Hendra, Nipah, Ebola and diseases caused by coronaviruses. Presumably because of their long history of coevolution, most of these viruses remain subclinical in bats, but have the potential to cause severe illnesses in domestic and wildlife animals and also humans. Spillovers from bats to humans either happen directly (via contact with infected bats) or indirectly (via intermediate hosts such as domestic or wildlife animals, by consuming food items contaminated by saliva, faeces or urine of bats, or via other environmental sources). Increasing numbers of breakouts of zoonotic viral diseases among humans and livestock have mainly been accounted to human encroachment into natural habitat, as well as agricultural intensification, deforestation and bushmeat consumption. Persecution of bats, including the destruction of their roosts and culling of whole colonies, has led not only to declines of protected bat species, but also to an increase in virus prevalence in some of these populations. Educational efforts are needed in order to prevent future spillovers of bat-borne viruses to humans and livestock, and to further protect bats from unnecessary and counterproductive culling.

Origin and evolution of Nipah virus

Nipah virus, member of the Paramyxoviridae family, is classified as a Biosafety Level-4 agent and category C priority pathogen. Nipah virus disease is endemic in south Asia and outbreaks have been reported in Malaysia, Singapore, India, and Bangladesh. Bats of the genus Pteropus appear to be the natural reservoir of this virus. The aim of this study was to investigate the genetic diversity of Nipah virus, to estimate the date of origin and the spread of the infection. The mean value of Nipah virus N gene evolutionary rate, was 6.5 × 10(-4) substitution/site/year (95% HPD: 2.3 × 10(-4)-1.18 × 10(-3)). The time-scaled phylogenetic analysis showed that the root of the tree originated in 1947 (95% HPD: 1888-1988) as the virus entered in south eastern Asiatic regions. The segregation of sequences in two main clades (I and II) indicating that Nipah virus had two different introductions: one in 1995 (95% HPD: 1985-2002) which correspond to clade I, and the other in 1985 (95% HPD: 1971-1996) which correspond to clade II. The phylogeographic reconstruction indicated that the epidemic followed two different routes spreading to the other locations. The trade of infected pigs may have played a role in the spread of the virus. Bats of the Pteropus genus, that are able to travel to long distances, may have contributed to the spread of the infection. Negatively selected sites, statistically supported, could reflect the stability of the viral N protein.

Oxidative stress in Nipah virus-infected human small airway epithelial cells

Nipah virus (NiV) is a zoonotic emerging pathogen that can cause severe and often fatal respiratory disease in humans. The pathogenesis of NiV infection of the human respiratory tract remains unknown. Reactive oxygen species (ROS) produced by airway epithelial cells in response to viral infections contribute to lung injury by inducing inflammation and oxidative stress; however, the role of ROS in NiV-induced respiratory disease is unknown. To investigate whether NiV induces oxidative stress in human respiratory epithelial cells, we used oxidative stress markers and monitored antioxidant gene expression. We also used ROS scavengers to assess their role in immune response modulation. Oxidative stress was confirmed in infected cells and correlated with the reduction in antioxidant enzyme gene expression. Infected cells treated by ROS scavengers resulted in a significant decrease of the (F2)-8-isoprostane marker, inflammatory responses and virus replication. In conclusion, ROS are induced during NiV infection in human respiratory epithelium and contribute to the inflammatory response. Understanding how oxidative stress contributes to NiV pathogenesis is crucial for therapeutic development.

A Computational Approach for Designing a Universal Epitope-Based Peptide Vaccine Against Nipah Virus

Nipah virus (NiV) is highly pathogenic single-stranded negative sense RNA virus. It can cause severe encephalitis and respiratory disease in humans. In addition, NiV infects a large range of host including mammals. As a result of its higher zoonotic potential and pathogenicity for human, it has been rated as an alert in recent days. A therapeutic treatment or vaccines has become elusive to fight against this virus. In this study, the attachment (G) and fusion (F) glycoproteins of NiV, responsible for the viral attachment and entry to the host cell, were selected to develop epitope-based vaccine against Nipah virus. Epitopes were identified from the conserved region of G and F protein of NiV. Both B-cell and T-cell immunity were checked to affirm it that these epitopes will be able to induce humoral and cellular immunity. A total of 6 T-cell epitopes and 19 significant HLA-epitope interactions were identified. Eventually it has shown an acceptable percentage in population coverage (46.45 %) and efficient binding with HLA molecule by molecular docking study.

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.

Controlling Nipah virus encephalitis in Bangladesh: Policy options

Nipah virus (NiV) encephalitis is endemic in Bangladesh, with yearly seasonal outbreaks occurring since 2003. NiV has a notable case fatality rate, 75-100 per cent depending on the strain. In Bangladesh, primary transmission to humans is believed to be because of consumption of bat-contaminated date palm sap (DPS). Both the disease and the virus have been investigated extensively, however efforts to implement preventive strategies have met social and cultural challenges. Here we present a variety of community approaches to control the spread of Nipah encephalitis, along with advantages and disadvantages of each. This information may be useful to health workers and policymakers in potential NiV outbreak areas in Southeast Asia.

Single-dose live-attenuated vesicular stomatitis virus-based vaccine protects African green monkeys from Nipah virus disease

Nipah virus is a zoonotic paramyxovirus that causes severe respiratory and/or encephalitic disease in humans, often resulting in death. It is transmitted from pteropus fruit bats, which serve as the natural reservoir of the virus, and outbreaks occur on an almost annual basis in Bangladesh or India. Outbreaks are small and sporadic, and several cases of human-to-human transmission have been documented as an important feature of the epidemiology of Nipah virus disease. There are no approved countermeasures to combat infection and medical intervention is supportive. We recently generated a recombinant replication-competent vesicular stomatitis virus-based vaccine that encodes a Nipah virus glycoprotein as an antigen and is highly efficacious in the hamster model of Nipah virus disease. Herein, we show that this vaccine protects African green monkeys, a well-characterized model of Nipah virus disease, from disease one month after a single intramuscular administration of the vaccine. Vaccination resulted in a rapid and strong virus-specific immune response which inhibited virus shedding and replication. This vaccine platform provides a rapid means to afford protection from Nipah virus in an outbreak situation.

Molecular recognition of human ephrinB2 cell surface receptor by an emergent African henipavirus

The discovery of African henipaviruses (HNVs) related to pathogenic Hendra virus (HeV) and Nipah virus (NiV) from Southeast Asia and Australia presents an open-ended health risk. Cell receptor use by emerging African HNVs at the stage of host-cell entry is a key parameter when considering the potential for spillover and infection of human populations. The attachment glycoprotein from a Ghanaian bat isolate (GhV-G) exhibits <30% sequence identity with Asiatic NiV-G/HeV-G. Here, through functional and structural analysis of GhV-G, we show how this African HNV targets the same human cell-surface receptor (ephrinB2) as the Asiatic HNVs. We first characterized this virus-receptor interaction crystallographically. Compared with extant HNV-G-ephrinB2 structures, there was significant structural variation in the six-bladed β-propeller scaffold of the GhV-G receptor-binding domain, but not the Greek key fold of the bound ephrinB2. Analysis revealed a surprisingly conserved mode of ephrinB2 interaction that reflects an ongoing evolutionary constraint among geographically distal and phylogenetically divergent HNVs to maintain the functionality of ephrinB2 recognition during virus-host entry. Interestingly, unlike NiV-G/HeV-G, we could not detect binding of GhV-G to ephrinB3. Comparative structure-function analysis further revealed several distinguishing features of HNV-G function: a secondary ephrinB2 interaction site that contributes to more efficient ephrinB2-mediated entry in NiV-G relative to GhV-G and cognate residues at the very C terminus of GhV-G (absent in Asiatic HNV-Gs) that are vital for efficient receptor-induced fusion, but not receptor binding per se. These data provide molecular-level details for evaluating the likelihood of African HNVs to spill over into human populations.

Detailed analysis of the African green monkey model of Nipah virus disease

Henipaviruses are implicated in severe and frequently fatal pneumonia and encephalitis in humans. There are no approved vaccines or treatments available for human use, and testing of candidates requires the use of well-characterized animal models that mimic human disease. We performed a comprehensive and statistically-powered evaluation of the African green monkey model to define parameters critical to disease progression and the extent to which they correlate with human disease. African green monkeys were inoculated by the intratracheal route with 2.5 × 10(4) plaque forming units of the Malaysia strain of Nipah virus. Physiological data captured using telemetry implants and assessed in conjunction with clinical pathology were consistent with shock, and histopathology confirmed widespread tissue involvement associated with systemic vasculitis in animals that succumbed to acute disease. In addition, relapse encephalitis was identified in 100% of animals that survived beyond the acute disease phase. Our data suggest that disease progression in the African green monkey is comparable to the variable outcome of Nipah virus infection in humans.

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.

Henipavirus pathogenesis and antiviral approaches

Hendra virus and Nipah virus are closely related, recently emerged zoonotic paramyxoviruses, belonging to the Henipavirus genus. Both viruses induce generalized vasculitis affecting particularly the respiratory tract and CNS. The exceptionally broad species tropism of Henipavirus, the high case fatality rate and person-to-person transmission associated with Nipah virus outbreaks emphasize the necessity of effective antiviral strategies for these intriguing threatening pathogens. Current therapeutic approaches, validated in animal models, target early steps in viral infection; they include the use of neutralizing virus-specific antibodies and blocking membrane fusion with peptides that bind the viral fusion protein. A better understanding of Henipavirus pathogenesis is critical for the further advancement of antiviral treatment, and we summarize here the recent progress in the field.

Infektionen

In diesem Kapitel werden zunächst die für die Neurointensivmedizin wesentlichen bakteriellen Infektionen (Meningitis, spinale und Hirnabszesse, Spondylodiszitis, septisch-embolische Herdenzephalitis) abgehandelt, die trotz gezielt eingesetzter Antibiotika und neurochirurgischer Therapieoptionen noch mit einer erheblichen Morbidität und Mortalität behaftet sind. Besonderheiten wie neurovaskuläre Komplikationen, die Tuberkulose des Nervensystems, Neuroborreliose, Neurosyphilis und opportunistische Infektionen bei Immunsuppressionszuständen finden hierbei besondere Berücksichtigung. Der zweite Teil dieses Kapitels behandelt akute und chronische Virusinfektionen des ZNS sowie in einem gesonderten Abschnitt die HIVInfektion und HIV-assoziierte Krankheitsbilder sowie Parasitosen und Pilzinfektionen, die in Industrieländern seit Einführung der HAART bei HIV zwar eher seltener, aber mit zunehmender Globalisierung auch in unseren Breiten immer noch anzutreffen sind.

A BSL-4 high-throughput screen identifies sulfonamide inhibitors of Nipah virus

Nipah virus is a biosafety level 4 (BSL-4) pathogen that causes severe respiratory illness and encephalitis in humans. To identify novel small molecules that target Nipah virus replication as potential therapeutics, Southern Research Institute and Galveston National Laboratory jointly developed an automated high-throughput screening platform that is capable of testing 10,000 compounds per day within BSL-4 biocontainment. Using this platform, we screened a 10,080-compound library using a cell-based, high-throughput screen for compounds that inhibited the virus-induced cytopathic effect. From this pilot effort, 23 compounds were identified with EC50 values ranging from 3.9 to 20.0 μM and selectivities >10. Three sulfonamide compounds with EC50 values <12 μM were further characterized for their point of intervention in the viral replication cycle and for broad antiviral efficacy. Development of HTS capability under BSL-4 containment changes the paradigm for drug discovery for highly pathogenic agents because this platform can be readily modified to identify prophylactic and postexposure therapeutic candidates against other BSL-4 pathogens, particularly Ebola, Marburg, and Lassa viruses.

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.

Efficient reverse genetics reveals genetic determinants of budding and fusogenic differences between Nipah and Hendra viruses and enables real-time monitoring of viral spread in small animal models of henipavirus infection

Nipah virus (NiV) and Hendra virus (HeV) are closely related henipaviruses of the Paramyxovirinae. Spillover from their fruit bat reservoirs can cause severe disease in humans and livestock. Despite their high sequence similarity, NiV and HeV exhibit apparent differences in receptor and tissue tropism, envelope-mediated fusogenicity, replicative fitness, and other pathophysiologic manifestations. To investigate the molecular basis for these differences, we first established a highly efficient reverse genetics system that increased rescue titers by ≥3 log units, which offset the difficulty of generating multiple recombinants under constraining biosafety level 4 (BSL-4) conditions. We then replaced, singly and in combination, the matrix (M), fusion (F), and attachment glycoprotein (G) genes in mCherry-expressing recombinant NiV (rNiV) with their HeV counterparts. These chimeric but isogenic rNiVs replicated well in primary human endothelial and neuronal cells, indicating efficient heterotypic complementation. The determinants of budding efficiency, fusogenicity, and replicative fitness were dissociable: HeV-M budded more efficiently than NiV-M, accounting for the higher replicative titers of HeV-M-bearing chimeras at early times, while the enhanced fusogenicity of NiV-G-bearing chimeras did not correlate with increased replicative fitness. Furthermore, to facilitate spatiotemporal studies on henipavirus pathogenesis, we generated a firefly luciferase-expressing NiV and monitored virus replication and spread in infected interferon alpha/beta receptor knockout mice via bioluminescence imaging. While intraperitoneal inoculation resulted in neuroinvasion following systemic spread and replication in the respiratory tract, intranasal inoculation resulted in confined spread to regions corresponding to olfactory bulbs and salivary glands before subsequent neuroinvasion. This optimized henipavirus reverse genetics system will facilitate future investigations into the growing numbers of novel henipavirus-like viruses.

IMPORTANCE

Nipah virus (NiV) and Hendra virus (HeV) are recently emergent zoonotic and highly lethal pathogens with pandemic potential. Although differences have been observed between NiV and HeV replication and pathogenesis, the molecular basis for these differences has not been examined. In this study, we established a highly efficient system to reverse engineer changes into replication-competent NiV and HeV, which facilitated the generation of reporter-expressing viruses and recombinant NiV-HeV chimeras with substitutions in the genes responsible for viral exit (the M gene, critical for assembly and budding) and viral entry (the G [attachment] and F [fusion] genes). These chimeras revealed differences in the budding and fusogenic properties of the M and G proteins, respectively, which help explain previously observed differences between NiV and HeV. Finally, to facilitate future in vivo studies, we monitored the replication and spread of a bioluminescent reporter-expressing NiV in susceptible mice; this is the first time such in vivo imaging has been performed under BSL-4 conditions.

Nipah viruses from Malaysia and Bangladesh: two of a kind?

ABSTRACT 

Nipah virus is a zoonotic paramyxovirus that has caused outbreaks of human disease with high fatality rates. Important differences in epidemiological features of human disease are associated with Nipah viruses isolated from Malaysia and Bangladesh, with person-to-person transmission a major pathway for infection in Bangladesh. Comparisons of Nipah virus isolates in vitro have demonstrated differences in regulation of innate immunity and replicative ability. In contrast, similarities in infection outcomes and tissue tropism in the ferret model indicate that differences between viral isolates may not be the pivotal determinants of Nipah virus transmission. Consideration and understanding of the social and cultural context within which Nipah virus outbreaks occur may be critical in the development of practical, achievable disease management strategies.

Emerging and reemerging neurologic infections

The list of emerging and reemerging pathogens that cause neurologic disease is expanding. Various factors, including population growth and a rise in international travel, have contributed to the spread of pathogens to previously nonendemic regions. Recent advances in diagnostic methods have led to the identification of novel pathogens responsible for infections of the central nervous system. Furthermore, new issues have arisen surrounding established infections, particularly in an increasingly immunocompromised population due to advances in the treatment of rheumatologic disease and in transplant medicine.

Syrian hamsters (Mesocricetus auratus) oronasally inoculated with a Nipah virus isolate from Bangladesh or Malaysia develop similar respiratory tract lesions

Nipah virus is a paramyxovirus in the genus Henipavirus, which has caused outbreaks in humans in Malaysia, India, Singapore, and Bangladesh. Whereas the human cases in Malaysia were characterized mainly by neurological symptoms and a case fatality rate of ∼40%, cases in Bangladesh also exhibited respiratory disease and had a case fatality rate of ∼70%. Here, we compared the histopathologic changes in the respiratory tract of Syrian hamsters, a well-established small animal disease model for Nipah virus, inoculated oronasally with Nipah virus isolates from human cases in Malaysia and Bangladesh. The Nipah virus isolate from Bangladesh caused slightly more severe rhinitis and bronchointerstitial pneumonia 2 days after inoculation in Syrian hamsters. By day 4, differences in lesion severity could no longer be detected. Immunohistochemistry demonstrated Nipah virus antigen in the nasal cavity and pulmonary lesions; the amount of Nipah virus antigen present correlated with lesion severity. Immunohistochemistry indicated that both Nipah virus isolates exhibited endotheliotropism in small- and medium-caliber arteries and arterioles, but not in veins, in the lung. This correlated with the location of ephrin B2, the main receptor for Nipah virus, in the vasculature. In conclusion, Nipah virus isolates from outbreaks in Malaysia and Bangladesh caused a similar type and severity of respiratory tract lesions in Syrian hamsters, suggesting that the differences in human disease reported in the outbreaks in Malaysia and Bangladesh are unlikely to have been caused by intrinsic differences in these 2 virus isolates.

Integrated cluster- and case-based surveillance for detecting stage III zoonotic pathogens: an example of Nipah virus surveillance in Bangladesh

This paper explores the utility of cluster- and case-based surveillance established in government hospitals in Bangladesh to detect Nipah virus, a stage III zoonotic pathogen. Physicians listed meningo-encephalitis cases in the 10 surveillance hospitals and identified a cluster when ⩾2 cases who lived within 30 min walking distance of one another developed symptoms within 3 weeks of each other. Physicians collected blood samples from the clustered cases. As part of case-based surveillance, blood was collected from all listed meningo-encephalitis cases in three hospitals during the Nipah season (January–March). An investigation team visited clustered cases’ communities to collect epidemiological information and blood from the living cases. We tested serum using Nipah-specific IgM ELISA. Up to September 2011, in 5887 listed cases, we identified 62 clusters comprising 176 encephalitis cases. We collected blood from 127 of these cases. In 10 clusters, we identified a total of 62 Nipah cases: 18 laboratory-confirmed and 34 probable. We identified person-to-person transmission of Nipah virus in four clusters. From case-based surveillance, we identified 23 (4%) Nipah cases. Faced with thousands of encephalitis cases, integrated cluster surveillance allows targeted deployment of investigative resources to detect outbreaks by stage III zoonotic pathogens in resource-limited settings.

Nine challenges in modelling the emergence of novel pathogens

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We summarize key challenges in modeling the emergence of novel infectious agents.

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We focus on connections to data, including epidemiologic and genetic data.

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Zoonoses are emphasized, because they are the source of most new human pathogens.

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Challenges span reservoir dynamics, cross-species spillover, and outbreak dynamics.

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Estimation of fatality rates and overall risk assessment are also addressed.

Studying the emergence of novel infectious agents involves many processes spanning host species, spatial scales, and scientific disciplines. Mathematical models play an essential role in combining insights from these investigations and drawing robust inferences from field and experimental data. We describe nine challenges in modelling the emergence of novel pathogens, emphasizing the interface between models and data.

Evaluation of transmission risks associated with in vivo replication of several high containment pathogens in a biosafety level 4 laboratory

Containment level 4 (CL4) laboratories studying biosafety level 4 viruses are under strict regulations to conduct nonhuman primate (NHP) studies in compliance of both animal welfare and biosafety requirements. NHPs housed in open-barred cages raise concerns about cross-contamination between animals, and accidental exposure of personnel to infectious materials. To address these concerns, two NHP experiments were performed. One examined the simultaneous infection of 6 groups of NHPs with 6 different viruses (Machupo, Junin, Rift Valley Fever, Crimean-Congo Hemorrhagic Fever, Nipah and Hendra viruses). Washing personnel between handling each NHP group, floor to ceiling biobubble with HEPA filter, and plexiglass between cages were employed for partial primary containment. The second experiment employed no primary containment around open barred cages with Ebola virus infected NHPs 0.3 meters from naïve NHPs. Viral antigen-specific ELISAs, qRT-PCR and TCID₅₀ infectious assays were utilized to determine antibody levels and viral loads. No transmission of virus to neighbouring NHPs was observed suggesting limited containment protocols are sufficient for multi-viral CL4 experiments within one room. The results support the concept that Ebola virus infection is self-contained in NHPs infected intramuscularly, at least in the present experimental conditions, and is not transmitted to naïve NHPs via an airborne route.

Prediction of epitope-based peptides for the utility of vaccine development from fusion and glycoprotein of nipah virus using in silico approach

This study aims to design epitope-based peptides for the utility of vaccine development by targeting glycoprotein G and envelope protein F of Nipah virus (NiV) that, respectively, facilitate attachment and fusion of NiV with host cells. Using various databases and tools, immune parameters of conserved sequence(s) from G and F proteins of different isolates of NiV were tested to predict probable epitope(s). Binding analyses of the peptides with MHC class-I and class-II molecules, epitope conservancy, population coverage, and linear B cell epitope prediction were analyzed. Predicted peptides interacted with seven or more MHC alleles and illustrated population coverage of more than 99% and 95%, for G and F proteins, respectively. The predicted class-I nonamers, SLIDTSSTI and EWISIVPNF, superimposed on the putative decameric B cell epitopes, were also identified as core sequences of the most probable class-II 15-mer peptides GPKVSLIDTSSTITI and EWISIVPNFILVRNT. These peptides were further validated for their binding to specific HLA alleles using in silico docking technique. Our in silico analysis suggested that the predicted epitopes, either GPKVSLIDTSSTITI or EWISIVPNFILVRNT, could be a better choice as universal vaccine component against NiV irrespective of different isolates which may elicit both humoral and cell-mediated immunity.

Piloting the promotion of bamboo skirt barriers to prevent Nipah virus transmission through date palm sap in Bangladesh

Drinking raw date palm sap contaminated with infected fruit bat saliva or urine is an important mode of Nipah virus transmission to humans in Bangladesh. Bamboo skirts are an effective way to interrupt bat access to the sap. We conducted a study from November 2008 to March 2009 to explore the effectiveness of higher- and lower-intensity interventions by promoting bamboo skirt preparation and use among sap harvesters (gachhis). We spent 280 person-hours in two villages for the higher-intensity intervention and half that amount of time in two other villages for the lower-intensity intervention. To evaluate the interventions we followed up all gachhis once a month for three months. A high percentage of gachhis (83% in higher-, 65% in lower-intensity interventions) prepared and used a skirt of bamboo or other materials - jute stalk, dhoincha (Sesbania aculeata), or polythene - at least once after intervention. In general, 15% of gachhis consistently used skirts throughout the sap collection season. The intensive nature of this intervention is very expensive for a large-scale programme. Future efforts should focus on developing a low-cost behaviour change intervention and evaluate if it reduces the human exposure to potentially contaminated fresh date palm sap.

A human lung xenograft mouse model of Nipah virus infection

Nipah virus (NiV) is a member of the genus Henipavirus (family Paramyxoviridae) that causes severe and often lethal respiratory illness and encephalitis in humans with high mortality rates (up to 92%). NiV can cause Acute Lung Injury (ALI) in humans, and human-to-human transmission has been observed in recent outbreaks of NiV. While the exact route of transmission to humans is not known, we have previously shown that NiV can efficiently infect human respiratory epithelial cells. The molecular mechanisms of NiV-associated ALI in the human respiratory tract are unknown. Thus, there is an urgent need for models of henipavirus infection of the human respiratory tract to study the pathogenesis and understand the host responses. Here, we describe a novel human lung xenograft model in mice to study the pathogenesis of NiV. Following transplantation, human fetal lung xenografts rapidly graft and develop mature structures of adult lungs including cartilage, vascular vessels, ciliated pseudostratified columnar epithelium, and primitive “air” spaces filled with mucus and lined by cuboidal to flat epithelium. Following infection, NiV grows to high titers (10⁷ TCID₅₀/gram lung tissue) as early as 3 days post infection (pi). NiV targets both the endothelium as well as respiratory epithelium in the human lung tissues, and results in syncytia formation. NiV infection in the human lung results in the production of several cytokines and chemokines including IL-6, IP-10, eotaxin, G-CSF and GM-CSF on days 5 and 7 pi. In conclusion, this study demonstrates that NiV can replicate to high titers in a novel in vivo model of the human respiratory tract, resulting in a robust inflammatory response, which is known to be associated with ALI. This model will facilitate progress in the fundamental understanding of henipavirus pathogenesis and virus-host interactions; it will also provide biologically relevant models for other respiratory viruses.

Nipah virus (NiV) is a highly pathogenic zoonotic virus that causes fatal disease in humans and a variety of other mammalian hosts including pigs. Given the lack of effective therapeutics and vaccines, this virus is considered a public health and agricultural concern, and listed as category C priority pathogen for biodefense research by the National Institute of Allergy and Infectious Diseases. Both animal-to-human and human-to-human transmission has been observed. Studies on the molecular mechanisms of NiV-mediated pathogenesis have been hampered by the lack of biologically relevant in vivo models for studying the initial host responses to NiV infection in the human lung. We show here a new small animal model in which we transplant human lung tissue for studying the pathogenesis of NiV. We showed that NiV can replicate to high levels in the human lung. NiV causes extensive damage to the lung tissue and induces important regulators of the inflammatory response. This study is the first to use a human lung transplant for studying infectious diseases, a powerful model for studying the pathogenesis of NiV infection, and will open up new possibilities for studying virus-host interactions.

Single-dose live-attenuated Nipah virus vaccines confer complete protection by eliciting antibodies directed against surface glycoproteins

BACKGROUND

Nipah virus (NiV), a zoonotic pathogen causing severe respiratory illness and encephalitis in humans, emerged in Malaysia in 1998 with subsequent outbreaks on an almost annual basis since 2001 in parts of the Indian subcontinent. The high case fatality rate, human-to-human transmission, wide-ranging reservoir distribution and lack of licensed intervention options are making NiV a serious regional and potential global public health problem. The objective of this study was to develop a fast-acting, single-dose NiV vaccine that could be implemented in a ring vaccination approach during outbreaks.

METHODS

In this study we have designed new live-attenuated vaccine vectors based on recombinant vesicular stomatitis viruses (rVSV) expressing NiV glycoproteins (G or F) or nucleoprotein (N) and evaluated their protective efficacy in Syrian hamsters, an established NiV animal disease model. We further characterized the humoral immune response to vaccination in hamsters using ELISA and neutralization assays and performed serum transfer studies.

RESULTS

Vaccination of Syrian hamsters with a single dose of the rVSV vaccine vectors resulted in strong humoral immune responses with neutralizing activities found only in those animals vaccinated with rVSV expressing NiV G or F proteins. Vaccinated animals with neutralizing antibody responses were completely protected from lethal NiV disease, whereas animals vaccinated with rVSV expressing NiV N showed only partial protection. Protection of NiV G or F vaccinated animals was conferred by antibodies, most likely the neutralizing fraction, as demonstrated by serum transfer studies. Protection of N-vaccinated hamsters was not antibody-dependent indicating a role of adaptive cellular responses for protection.

CONCLUSIONS

The rVSV vectors expressing Nipah virus G or F are prime candidates for new 'emergency vaccines' to be utilized for NiV outbreak management.

Family caregivers in public tertiary care hospitals in Bangladesh: risks and opportunities for infection control

Background

Family caregivers are integral to patient care in Bangladeshi public hospitals. This study explored family caregivers' activities and their perceptions and practices related to disease transmission and prevention in public hospitals.

Methods

Trained qualitative researchers conducted a total of 48 hours of observation in 3 public tertiary care hospitals and 12 in-depth interviews with family caregivers.

Results

Family caregivers provided care 24 hours a day, including bedside nursing, cleaning care, and psychologic support. During observations, family members provided 2,065 episodes of care giving, 75% (1,544) of which involved close contact with patients. We observed family caregivers washing their hands with soap on only 4 occasions. The majority of respondents said diseases are transmitted through physical contact with surfaces and objects that have been contaminated with patient secretions and excretions, and avoiding contact with these contaminated objects would help prevent disease.

Conclusion

Family caregivers are at risk for hospital-acquired infection from their repeated exposure to infectious agents combined with their inadequate hand hygiene and knowledge about disease transmission. Future research should explore potential strategies to improve family caregivers' knowledge about disease transmission and reduce family caregiver exposures, which may be accomplished by improving care provided by health care workers.

Recent developments in experimental animal models of Henipavirus infection

Hendra (HeV) and Nipah (NiV) viruses (genus Henipavirus (HNV; family Paramyxoviridae) are emerging zoonotic agents that can cause severe respiratory distress and acute encephalitis in humans. Given the lack of effective therapeutics and vaccines for human use, these viruses are considered as public health concerns. Several experimental animal models of HNV infection have been developed in recent years. Here, we review the current status of four of the most promising experimental animal models (mice, hamsters, ferrets, and African green monkeys) and their suitability for modeling the clinical disease, transmission, pathogenesis, prevention, and treatment for HNV infection in humans.

Infrastructure and contamination of the physical environment in three Bangladeshi hospitals: putting infection control into context

Objective

This paper describes the physical structure and environmental contamination in selected hospital wards in three government hospitals in Bangladesh.

Methods

The qualitative research team conducted 48 hours of observation in six wards from three Bangladeshi tertiary hospitals in 2007. They recorded environmental contamination with body secretions and excretions and medical waste and observed ward occupant handwashing and use of personal protective equipment. They recorded number of persons, number of open doors and windows, and use of fans. They measured the ward area and informally observed waste disposal outside the wards. They conducted nine focus group discussions with doctors, nurses and support staff.

Results

A median of 3.7 persons were present per 10 m² of floor space in the wards. A median of 4.9 uncovered coughs or sneezes were recorded per 10 m² per hour per ward. Floors in the wards were soiled with saliva, spit, mucous, vomitus, feces and blood 125 times in 48 hours. Only two of the 12 patient handwashing stations had running water and none had soap. No disinfection was observed before or after using medical instruments. Used medical supplies were often discarded in open containers under the beds. Handwashing with soap was observed in only 32 of 3,373 handwashing opportunities noted during 48 hours. Mosquitoes and feral cats were commonly observed in the wards.

Conclusions

The physical structure and environment of our study hospitals are conducive to the spread of infection to people in the wards. Low-cost interventions on hand hygiene and cleaning procedures for rooms and medical equipment should be developed and evaluated for their practicality and effectiveness.

Assessing the risk of Nipah virus establishment in Australian flying-foxes

Nipah virus (NiV) is a recently emerged zoonotic virus that causes severe disease in humans. The reservoir hosts for NiV, bats of the genus Pteropus (known as flying-foxes) are found across the Asia-Pacific including Australia. While NiV has not been detected in Australia, evidence for NiV infection has been found in flying-foxes in some of Australia's closest neighbours. A qualitative risk assessment was undertaken to assess the risk of NiV establishing in Australian flying-foxes through flying-fox movements from nearby regions. Events surrounding the emergence of new diseases are typically uncertain and in this study an expert opinion workshop was used to address gaps in knowledge. Given the difficulties in combining expert opinion, five different combination methods were analysed to assess their influence on the risk outcome. Under the baseline scenario where the median was used to combine opinions, the risk was estimated to be very low. However, this risk increased when the mean and linear opinion pooling combination methods were used. This assessment highlights the effects that different methods for combining expert opinion have on final risk estimates and the caution needed when interpreting these outcomes given the high degree of uncertainty in expert opinion. This work has provided a flexible model framework for assessing the risk of NiV establishment in Australian flying-foxes through bat movements which can be updated when new data become available.

Single injection recombinant vesicular stomatitis virus vaccines protect ferrets against lethal Nipah virus disease

Background

Nipah virus (NiV) is a highly pathogenic zoonotic agent in the family Paramyxoviridae that is maintained in nature by bats. Outbreaks have occurred in Malaysia, Singapore, India, and Bangladesh and have been associated with 40 to 75% case fatality rates. There are currently no vaccines or postexposure treatments licensed for combating human NiV infection.

Methods and results

Four groups of ferrets received a single vaccination with different recombinant vesicular stomatitis virus vectors expressing: Group 1, control with no glycoprotein; Group 2, the NiV fusion protein (F); Group 3, the NiV attachment protein (G); and Group 4, a combination of the NiV F and G proteins. Animals were challenged intranasally with NiV 28 days after vaccination. Control ferrets in Group 1 showed characteristic clinical signs of NiV disease including respiratory distress, neurological disorders, viral load in blood and tissues, and gross lesions and antigen in target tissues; all animals in this group succumbed to infection by day 8. Importantly, all specifically vaccinated ferrets in Groups 2-4 showed no evidence of clinical illness and survived challenged. All animals in these groups developed anti-NiV F and/or G IgG and neutralizing antibody titers. While NiV RNA was detected in blood at day 6 post challenge in animals from Groups 2-4, the levels were orders of magnitude lower than animals from control Group 1.

Conclusions

These data show protective efficacy against NiV in a relevant model of human infection. Further development of this technology has the potential to yield effective single injection vaccines for NiV infection.

Crystal structure of the Hendra virus attachment G glycoprotein bound to a potent cross-reactive neutralizing human monoclonal antibody

The henipaviruses, represented by Hendra (HeV) and Nipah (NiV) viruses are highly pathogenic zoonotic paramyxoviruses with uniquely broad host tropisms responsible for repeated outbreaks in Australia, Southeast Asia, India and Bangladesh. The high morbidity and mortality rates associated with infection and lack of licensed antiviral therapies make the henipaviruses a potential biological threat to humans and livestock. Henipavirus entry is initiated by the attachment of the G envelope glycoprotein to host cell membrane receptors. Previously, henipavirus-neutralizing human monoclonal antibodies (hmAb) have been isolated using the HeV-G glycoprotein and a human naïve antibody library. One cross-reactive and receptor-blocking hmAb (m102.4) was recently demonstrated to be an effective post-exposure therapy in two animal models of NiV and HeV infection, has been used in several people on a compassionate use basis, and is currently in development for use in humans. Here, we report the crystal structure of the complex of HeV-G with m102.3, an m102.4 derivative, and describe NiV and HeV escape mutants. This structure provides detailed insight into the mechanism of HeV and NiV neutralization by m102.4, and serves as a blueprint for further optimization of m102.4 as a therapeutic agent and for the development of entry inhibitors and vaccines.

Since their initial emergence, henipaviruses have continued to cause spillover events in both human and livestock populations, posing significant biothreats. Currently there are no licensed or approved therapies for treatment of henipavirus infection and the human case mortality rates average >70%. We used X-ray crystallography to determine the high-resolution structures of the Hendra virus G glycoprotein in complex with a cross-reactive neutralizing human monoclonal antibody. The structures provide detailed insight into the mechanism of HeV and NiV neutralization by this potent and clinically-relevant human monoclonal antibody that is currently in development for use in humans. This monoclonal antibody was recently shown to be an effective post-exposure therapy in non-human models of lethal Hendra virus infection. Indeed, it has already been used in four people on a compassionate use request, three in Australia and one in the United States, as a therapeutic agent. Furthermore, we identified and characterized two escape mutants generated in vitro and evaluated their mechanism of escape. Our results serve as a blueprint for further optimization of this antibody and for the development of novel entry inhibitors and vaccines. This report also supports the additional pre-clinical data required for eventual licensure by detailing the antibody's mechanism of henipavirus neutralization.

Hendra and Nipah infection: emerging paramyxoviruses

Since their first emergence in mid 1990s henipaviruses continued to re emerge in Australia and South East Asia almost every year. In total there has been more than 12 Nipah and 48 Hendra virus outbreaks reported in South East Asia and Australia, respectively. These outbreaks are associated with significant economic and health damages that most high risks countries (particularly in South East Asia) cannot bear the burden of such economical threats. Up until recently, there were no actual therapeutics available to treat or prevent these lethal infections. However, an international collaborative research has resulted in the identification of a potential equine Hendra vaccine capable of providing antibody protection against Hendra virus infections. Consequently, with the current findings and after nearly 2 decades since their first detection, are we there yet? This review recaps the chronicle of the henipavirus emergence and briefly evaluates potential anti-henipavirus vaccines and antivirals.

The pandemic potential of Nipah virus

Nipah virus, a paramyxovirus whose wildlife reservoir is Pteropus bats, was first discovered in a large outbreak of acute encephalitis in Malaysia in 1998 among persons who had contact with sick pigs. Apparently, one or more pigs was infected from bats, and the virus then spread efficiently from pig to pig, then from pigs to people. Nipah virus outbreaks have been recognized nearly every year in Bangladesh since 2001 and occasionally in neighboring India. Outbreaks in Bangladesh and India have been characterized by frequent person-to-person transmission and the death of over 70% of infected people. Characteristics of Nipah virus that increase its risk of becoming a global pandemic include: humans are already susceptible; many strains are capable of limited person-to-person transmission; as an RNA virus, it has an exceptionally high rate of mutation: and that if a human-adapted strain were to infect communities in South Asia, high population densities and global interconnectedness would rapidly spread the infection. Appropriate steps to estimate and manage this risk include studies to explore the molecular and genetic basis of respiratory transmission of henipaviruses, improved surveillance for human infections, support from high-income countries to reduce the risk of person-to-person transmission of infectious agents in low-income health care settings, and consideration of vaccination in communities at ongoing risk of exposure to the secretions and excretions of Pteropus bats.

Nipah virus infection outbreak with nosocomial and corpse-to-human transmission, Bangladesh

Particularly vulnerable are health care workers who do not use personal protective equipment and persons who do not wash hands after traditional burial practices.

Active Nipah virus encephalitis surveillance identified an encephalitis cluster and sporadic cases in Faridpur, Bangladesh, in January 2010. We identified 16 case-patients; 14 of these patients died. For 1 case-patient, the only known exposure was hugging a deceased patient with a probable case, while another case-patient’s exposure involved preparing the same corpse for burial by removing oral secretions and anogenital excreta with a cloth and bare hands. Among 7 persons with confirmed sporadic cases, 6 died, including a physician who had physically examined encephalitis patients without gloves or a mask. Nipah virus–infected patients were more likely than community-based controls to report drinking raw date palm sap and to have had physical contact with an encephalitis patient (29% vs. 4%, matched odds ratio undefined). Efforts to prevent transmission should focus on reducing caregivers’ exposure to infected patients’ bodily secretions during care and traditional burial practices.

Potent inhibition of Hendra virus infection via RNA interference and poly I:C immune activation

Hendra virus (HeV) is a highly pathogenic zoonotic paramyxovirus that causes fatal disease in a wide range of species, including humans. HeV was first described in Australia in 1994, and has continued to re-emerge with increasing frequency. HeV is of significant concern to human health due to its high mortality rate, increasing emergence, absence of vaccines and limited post exposure therapies. Here we investigate the use of RNA interference (RNAi) based therapeutics targeting HeV in conjunction with the TLR3 agonist Poly I:C and show that they are potent inhibitors of HeV infection in vitro. We found that short interfering RNAs (siRNAs) targeting the abundantly expressed N, P and M genes of HeV caused over 95% reduction of HeV virus titre, protein and mRNA. Furthermore, we found that the combination of HeV targeting siRNA and Poly I:C had an additive effect in suppressing HeV infection. Our results demonstrate for the first time that RNAi and type I interferon stimulation are effective inhibitors of HeV replication in vitro and may provide an effective therapy for this highly lethal, zoonotic pathogen.

Threats to Bats and Educational Challenges

Like most animals, bats are threatened by habitat loss and degradation. However, they are also uniquely threatened almost universally by humans. In this chapter, I will emphasize the educational issues I believe will be most important to the next generation of bat conservationists. Though threat levels and possible solutions vary widely, the importance of addressing unfounded fear cannot be ignored. Putting disease concerns in perspective has been essential throughout the history of bat conservation efforts and is currently a resurgent issue that threatens the educational progress that has been made in recent decades.

Activation and cell death in human dendritic cells infected with Nipah virus

Nipah virus (NiV) is a highly pathogenic paramyxovirus that causes pulmonary disease and encephalitis in humans with 40-70% fatality. Interactions between NiV and the human immune system remain poorly understood. Here, we demonstrate the effects of NiV infection on DC and T cell function. Using an in vitro system, we found that NiV infects and replicates at low levels in DCs and induces the expression of TNF-α, IL-1α, IL-1β, IL-8, and IP-10. NiV infection activates DCs, and upregulates the expression of CD40, CD80, and CD86. Also have reduced levels of bcl2 and high levels of active caspase 3, suggesting the induction of apoptosis. DCs infected by NiV are unable to efficiently prime CD4 and CD8 T cells, but instead induce apoptosis in T cells. Interestingly, DCs treated with inactivated NiV also show signs of apoptosis. These findings indicate that NiV infected DCs could play an important role in NiV pathogenesis.

Recombinant Hendra viruses expressing a reporter gene retain pathogenicity in ferrets

Background

Hendra virus (HeV) is an Australian bat-borne zoonotic paramyxovirus that repeatedly spills-over to horses causing fatal disease. Human cases have all been associated with close contact with infected horses.

Methods

A full-length antigenome clone of HeV was assembled, a reporter gene (GFP or luciferase) inserted between the P and M genes and transfected to 293T cells to generate infectious reporter gene-encoding recombinant viruses. These viruses were then assessed in vitro for expression of the reporter genes. The GFP expressing recombinant HeV was used to challenge ferrets to assess the virulence and tissue distribution by monitoring GFP expression in infected cells.

Results

Three recombinant HeV constructs were successfully cloned and rescued; a wild-type virus, a GFP-expressing virus and a firefly luciferase-expressing virus. In vitro characterisation demonstrated expression of the reporter genes, with levels proportional to the initial inoculum levels. Challenge of ferrets with the GFP virus demonstrated maintenance of the fatal phenotype with disease progressing to death consistent with that observed previously with the parental wild-type isolate of HeV. GFP expression could be observed in infected tissues collected from animals at euthanasia.

Conclusions

Here, we report on the first successful rescue of recombinant HeV, including wild-type virus and viruses expressing two different reporter genes encoded as an additional gene cassette inserted between the P and M genes. We further demonstrate that the GFP virus retained the ability to cause fatal disease in a well-characterized ferret model of henipavirus infection despite the genome being an extra 1290 nucleotides in length.

Legal, technical, and interpretational considerations in the forensic analysis of viruses

The forensic evaluation of viruses presents new challenges to the forensic science community. Although many criminal cases have been adjudicated involving the deliberate transmission of viruses, especially HIV, this review provides a general approach to viral forensics, especially in light of significant biodefense challenges. Newly emerging techniques of nucleic acid sequencing are discussed in a forensic context. Human mitochondrial DNA analysis, wherein mixed profiles are routinely assessed in a forensic context, provides the groundwork for an interpretational approach to the issue of mixed DNA sequences. The importance of phylogenetic classification is discussed as both providing an integrated graphical depiction of the structure of viral nucleic acid variation as well as offering a tool that can be used to assess the relatedness of complex populations of nucleic acids.