Bat Virus Research Articles

Frugivorous bats in the Colombian Caribbean region are reservoirs of the rabies virus

BackgroundBats are an important ecological group within ecosystems. The rabies virus is a Lyssavirus, and haematophagous bats are the principal reservoir; however, the virus has also been detected in non-haematophagous bats. The objective was to determine the rabies virus in non-haematophagous bats in the Colombian Caribbean region.MethodsIn 2017, a cross-sectional study was carried out with a base-risk sampling in twelve geographic zones of the Colombian Caribbean area that included the main ecosystems of two departments. 286 bats were captured, which were euthanized with a pharmacological treatment following the ethical protocols of animal experimentation. The taxonomic identification was done with dichotomous keys. The necropsy was carried out at the capture site, and brain samples were kept in liquid nitrogen. The extraction of the RNA was carried out from the frozen brains with Trizol™; a fragment of 914 bp of the glycoprotein G of the rabies virus was amplified with RT-PCR. The amplicons were sequenced with the Sanger method.ResultsTwenty-three genera of bats were identified, and, in two frugivorous, Artibeus lituratus and Artibeus planirostris, amplicons were obtained and sequenced as the rabies virus.ConclusionsThis is the first evidence of natural infection of the rabies virus in frugivorous bats in the Colombian Caribbean area; this result is important for the surveillance and control of rabies.

Diversity and Evolution of Viral Pathogen Community in Cave Nectar Bats (Eonycteris spelaea).

Bats are unique mammals, exhibit distinctive life history traits and have unique immunological approaches to suppression of viral diseases upon infection. High-throughput next-generation sequencing has been used in characterizing the virome of different bat species. The cave nectar bat, Eonycteris spelaea, has a broad geographical range across Southeast Asia, India and southern China, however, little is known about their involvement in virus transmission. Here we investigate the diversity and abundance of viral communities from a colony of Eonycteris spelaea residing in Singapore. Our results detected 47 and 22 different virus families from bat fecal and urine samples, respectively. Among these, we identify a large number of virus families including Adenoviridae, Flaviviridae, Reoviridae, Papillomaviridae, Paramyxoviridae, Parvoviridae, Picornaviridae, and Polyomaviridae. In most cases, viral sequences from Eonycteris spelaea are genetically related to a group of bat viruses from other bat genera (e.g., Eidolon, Miniopterus, Rhinolophus and Rousettus). The results of this study improve our knowledge of the host range, spread and evolution of several important viral pathogens. More significantly, our findings provide a baseline to study the temporal patterns of virus shedding and how they correlate with bat phenological trends.

Metagenomic analysis of bat virome in the Guangxi-Vietnam border area

The areas covering Guangxi, China and Vietnam have greatly and geographically strategic importance. These areas have abundant bat resources with many harboring diverse zoonotic viruses. In order to monitor the cross-border transmission of bat viruses in the Guangxi-Vietnam border area and to prevent potential emerging infectious diseases caused by bat viruses, understanding the bat virus diversity and their evolution are greatly necessary. Here we conducted viral metagenomic analysis of bats sampled in the border area, and results revealed 49 families of viruses, including those infecting vertebrate, plants, insects and bacteria. Additionally, we screened hepadnavirus, bocaparvovirus, group A rotavirus, astrovirus, rhabdovirus and coronavirus in those bat samples, and phylogenetically analyzed those amplicons. Results showed that astroviruses were widely present in those animals with great genetic diversity, but other viruses were only detected in some specific bats. Bocaparvoviruses and rhabdoviruses were significantly divergent from currently known viruses, and possibly were prototypes of new species. Notably, group A viruses identified here shared high identity with a human virus, suggestive of inter-species transmission and reassortment. The present study profiled the viromic composition harbored by bats in Guangxi-Vietnam border area, and inspected epidemiological situation and evolutionary characteristics of some viruses. Those findings provide fundamental data to cross-border transmission of bat viruses and predict bat virus-related zoonotic potentials.

Immune System Modulation and Viral Persistence in Bats: Understanding Viral Spillover.

Bats harbor a myriad of viruses and some of these viruses may have spilled over to other species including humans. Spillover events are rare and several factors must align to create the “perfect storm” that would ultimately lead to a spillover. One of these factors is the increased shedding of virus by bats. Several studies have indicated that bats have unique defense mechanisms that allow them to be persistently or latently infected with viruses. Factors leading to an increase in the viral load of persistently infected bats would facilitate shedding of virus. This article reviews the unique nature of bat immune defenses that regulate virus replication and the various molecular mechanisms that play a role in altering the balanced bat–virus relationship.

Bats and Viruses: Emergence of Novel Lyssaviruses and Association of Bats with Viral Zoonoses in the EU.

Bats in the EU have been associated with several zoonotic viral pathogens of significance to both human and animal health. Virus discovery continues to expand the existing understating of virus classification, and the increased interest in bats globally as reservoirs or carriers of zoonotic agents has fuelled the continued detection and characterisation of new lyssaviruses and other viral zoonoses. Although the transmission of lyssaviruses from bat species to humans or terrestrial species appears rare, interest in these viruses remains, through their ability to cause the invariably fatal encephalitis—rabies. The association of bats with other viral zoonoses is also of great interest. Much of the EU is free of terrestrial rabies, but several bat species harbor lyssaviruses that remain a risk to human and animal health. Whilst the rabies virus is the main cause of rabies globally, novel related viruses continue to be discovered, predominantly in bat populations, that are of interest purely through their classification within the lyssavirus genus alongside the rabies virus. Although the rabies virus is principally transmitted from the bite of infected dogs, these related lyssaviruses are primarily transmitted to humans and terrestrial carnivores by bats. Even though reports of zoonotic viruses from bats within the EU are rare, to protect human and animal health, it is important characterise novel bat viruses for several reasons, namely: (i) to investigate the mechanisms for the maintenance, potential routes of transmission, and resulting clinical signs, if any, in their natural hosts; (ii) to investigate the ability of existing vaccines, where available, to protect against these viruses; (iii) to evaluate the potential for spill over and onward transmission of viral pathogens in novel terrestrial hosts. This review is an update on the current situation regarding zoonotic virus discovery within bats in the EU, and provides details of potential future mechanisms to control the threat from these deadly pathogens.

Gut Virome Analysis of Cameroonians Reveals High Diversity of Enteric Viruses, Including Potential Interspecies Transmitted Viruses.

Diarrhea remains one of the most common causes of deaths in children. A limited number of studies have investigated the prevalence of enteric pathogens in Cameroon, and as in many other African countries, the cause of many diarrheal episodes remains unexplained. A proportion of these unknown cases of diarrhea are likely caused by yet-unidentified viral agents, some of which could be the result of (recent) interspecies transmission from animal reservoirs, like bats. Using viral metagenomics, we screened fecal samples of 221 humans (almost all with gastroenteritis symptoms) between 0 and 89 years of age with different degrees of bat contact. We identified viruses belonging to families that are known to cause gastroenteritis such as Adenoviridae, Astroviridae, Caliciviridae, Picornaviridae, and Reoviridae Interestingly, a mammalian orthoreovirus, picobirnaviruses, a smacovirus, and a pecovirus were also found. Although there was no evidence of interspecies transmission of the most common human gastroenteritis-related viruses (Astroviridae, Caliciviridae, and Reoviridae), the phylogenies of the identified orthoreovirus, picobirnavirus, and smacovirus indicate a genetic relatedness of these viruses identified in stools of humans and those of bats and/or other animals. These findings points out the possibility of interspecies transmission or simply a shared host of these viruses (bacterial, fungal, parasitic, …) present in both animals (bats) and humans. Further screening of bat viruses in humans or vice versa will elucidate the epidemiological potential threats of animal viruses to human health. Furthermore, this study showed a huge diversity of highly divergent novel phages, thereby expanding the existing phageome considerably.IMPORTANCE Despite the availability of diagnostic tools for different enteric viral pathogens, a large fraction of human cases of gastroenteritis remains unexplained. This could be due to pathogens not tested for or novel divergent viruses of potential animal origin. Fecal virome analyses of Cameroonians showed a very diverse group of viruses, some of which are genetically related to those identified in animals. This is the first attempt to describe the gut virome of humans from Cameroon. Therefore, the data represent a baseline for future studies on enteric viral pathogens in this area and contribute to our knowledge of the world's virome. The studies also highlight the fact that more viruses may be associated with diarrhea than the typical known ones. Hence, it provides meaningful epidemiological information on diarrhea-related viruses in this area.

Co-Circulation and Excretion Dynamics of Diverse Rubula- and Related Viruses in Egyptian Rousette Bats from South Africa.

The Egyptian rousette bat (Rousettus aegyptiacus) has previously been implicated as the natural host of a zoonotic rubulavirus; however, its association with rubulaviruses has been studied to a limited extent. Urine, spleen, and other organs collected from the R. aegyptiacus population within South Africa were tested with a hemi-nested RT-PCR assay targeting a partial polymerase gene region of viruses from the Avula- and Rubulavirus genera. Urine was collected over a 14-month period to study the temporal dynamics of viral excretion. Diverse rubulaviruses, including viruses related to human mumps and parainfluenza virus 2, were detected. Active excretion was identified during two peak periods coinciding with the host reproductive cycle. Analysis of additional organs indicated co-infection of individual bats with a number of different putative rubulaviruses, highlighting the limitations of using a single sample type when determining viral presence and diversity. Our findings suggest that R. aegyptiacus can harbor a range of Rubula- and related viruses, some of which are related to known human pathogens. The observed peaks in viral excretion represents potential periods of a higher risk of virus transmission and zoonotic disease spill-over.

Isolation and Full-Genome Characterization of Nipah Viruses from Bats, Bangladesh.

Despite molecular and serologic evidence of Nipah virus in bats from various locations, attempts to isolate live virus have been largely unsuccessful. We report isolation and full-genome characterization of 10 Nipah virus isolates from Pteropus medius bats sampled in Bangladesh during 2013 and 2014.

Lyssavirus Spp. – Rabies Viruses As A Still-Present Problem

Abstract The genus Lyssavirus spp. currently includes 14 species that are responsible for causing rabies, rabies-like and rabies-related diseases. The first symptoms of infection are similar to a cold and mainly include fever, headache and general fatigue. Then comes brain dysfunction and acute neurological symptoms, and ultimately – in most cases – death. Lyssaviruses are spread mainly through direct contact with the carrier that contains the viral reservoir. The gold standard in diagnostics is the method of direct immunofluorescence, through which viral antigens are detected – mainly in the saliva of a patient. Currently, rabies treatment is an experimental form of therapy according to the Milwaukee protocol. 1. Introduction. 2. Systematics. 2.1. Lagos bat virus. 2.2. Mokola virus. 2.3 Duvenhage virus. 2.4. European bat 1 lyssavirus. 2.5. European bat 2 lyssavirus. 2.6. Australian bat lyssavirus. 3. Characteristics. 3.1. Molecular structure. 3.2. Genome and gene expression. 3.3. Life cycle. 4. Pathogenicity. 4.1. Pathogenesis. 4.2. Rabies symptoms. 5. Prevention, prophylaxis, diagnostics, treatment. 5.1. Vaccinations. 5.2. Postexposure prophylaxis. 5.3. Diagnostics. 5.4. Experimental treatment. 6. Summary

Arousal from hibernation and reactivation of Eptesicus fuscus gammaherpesvirus (EfHV) in big brown bats.

Many viruses that cause serious and often fatal disease in humans have spilled over from bats. Recent evidence suggests that stress may enhance virus shedding by bats increasing the possibility of transmission to other species. To understand the reasons for spillover is therefore important to determine the molecular pathways that link stress to virus reactivation and shedding in bats. We recently isolated and characterized a gammaherpesvirus (Eptesicus fuscus herpesvirus, EfHV) autochthonous to North American big brown bats. Since herpesviruses are known to reactivate from latent infections in response to a wide variety of stressors, EfHV presents us with an opportunity to study how physiological, behavioural or environmental changes may influence the big brown bats' relationship with EfHV. To understand the biology of the virus and how the extended periods of torpor experienced by these bats during hibernation along with the stress of arousal might influence the virus-host relationship, we attempted to detect the virus in the blood of wild-caught non-hibernating bats as well as captive bats arising from hibernation. We compared the prevalence of EfHV in the blood (using PCR) and EfHV-specific antibodies (using ELISA) between captive hibernating bats and wild-caught non-hibernating bats. We detected EfHV only in the blood of captive hibernating bats (27.8%=10/36) and not in wild-caught non-hibernating bats (0.0%=0/43). In contrast, the EfHV-specific antibody titres were higher in the non-hibernating bats compared to the hibernating bats. Our study suggests that: (a) viral DNA in blood indicates reactivation from latency, (b) long periods of hibernation lead to suppression of immunity, (c) stress of arousal from hibernation reactivates the virus in bats with lower levels of anti-viral immunity (indicated by humoral immune response), and (d) levels of anti-viral immunity increase in non-hibernating bats following reactivation.

Eco-epidemiology of the Venezuelan equine encephalitis virus in bats of Córdoba and Sucre, Colombia

Alphavirus infection associated encephalitis is an emerging infectious disease with a high impact on public health in Latin America. ObjectiveTo study the eco-epidemiology of alphaviruses in bats of departments of Córdoba and Sucre, Colombia. MethodologyA prospective descriptive cross-sectional study with a non-probabilistic sampling, in 12 localities of Córdoba and Sucre was carried out. Using mist nets capture of the specimens was carried out. The size of the sample was 286 bats, each specimen captured was taxonomically classified. The bats were immobilized with anesthetic and analgesic treatment according to the ethics committee of the University of Córdoba, morphometric measurements and blood samples were taken, later they were necropsied in the field to obtain a collection of tissues which were preserved in liquid N2 −190 °C. The averages of the climatic conditions of the sampling sites were extracted from the WorldClim database (http://www.worldclim.org/). The open source software QGIS (Quantum GIS Development Team.2015) was used to map and visualize bioclimatic regions of Córdoba. We used descriptive and retrospective information about the equine population and reports of foci of equine encephalitis. ResultsIn Córdoba and Sucre, 286 bats were captured and 23 species were classified, Artibeus and Phyllostomus discolor were the most frequent captured genus. The geographic ranges of the captured species were variable, some had a wide distribution and others were restricted to some areas. Venezuelan equine encephalitis virus RNA was detected in Artibeus planirostris and Sturnira lilium (2/286 = 0.70%) from Cordoba – Colombia. The univariate descriptive analysis showed no significant association for any of the analyzed variables climatic. ConclusionsFrugivorous bats from the Caribbean area of Colombia may be involved in the Venezuelan equine encephalitis virus enzootic cycle.

Replication of MERS and SARS coronaviruses in bat cells offers insights to their ancestral origins

Previous findings of Middle East Respiratory Syndrome coronavirus (MERS-CoV)-related viruses in bats, and the ability of Tylonycteris-BatCoV HKU4 spike protein to utilize MERS-CoV receptor, human dipeptidyl peptidase 4 hDPP4, suggest a bat ancestral origin of MERS-CoV. We developed 12 primary bat cell lines from seven bat species, including Tylonycteris pachypus, Pipistrellus abramus and Rhinolophus sinicus (hosts of Tylonycteris-BatCoV HKU4, Pipistrellus-BatCoV HKU5, and SARS-related-CoV respectively), and tested their susceptibilities to MERS-CoVs, SARS-CoV, and human coronavirus 229E (HCoV-229E). Five cell lines, including P. abramus and R. sinicus but not T. pachypus cells, were susceptible to human MERS-CoV EMC/2012. However, three tested camel MERS-CoV strains showed different infectivities, with only two strains capable of infecting three and one cell lines respectively. SARS-CoV can only replicate in R. sinicus cells, while HCoV-229E cannot replicate in any bat cells. Bat dipeptidyl peptidase 4 (DPP4) sequences were closely related to those of human and non-human primates but distinct from dromedary DPP4 sequence. Critical residues for binding to MERS-CoV spike protein were mostly conserved in bat DPP4. DPP4 was expressed in the five bat cells susceptible to MERS-CoV, with significantly higher mRNA expression levels than those in non-susceptible cells (P = 0.0174), supporting that DPP4 expression is critical for MERS-CoV infection in bats. However, overexpression of T. pachypus DPP4 failed to confer MERS-CoV susceptibility in T. pachypus cells, suggesting other cellular factors in determining viral replication. The broad cellular tropism of MERS-CoV should prompt further exploration of host diversity of related viruses to identify its ancestral origin.

Survey of Ebola Viruses in Frugivorous and Insectivorous Bats in Guinea, Cameroon, and the Democratic Republic of the Congo, 2015-2017.

To clarify the role of bats in the ecology of Ebola viruses, we assessed the prevalence of Ebola virus antibodies in a large-scale sample of bats collected during 2015–2017 from countries in Africa that have had previous Ebola outbreaks (Guinea, the Democratic Republic of the Congo) or are at high risk for outbreaks (Cameroon). We analyzed 4,022 blood samples of bats from >12 frugivorous and 27 insectivorous species; 2–37 (0.05%–0.92%) bats were seropositive for Zaire and 0–30 (0%–0.75%) bats for Sudan Ebola viruses. We observed Ebola virus antibodies in 1 insectivorous bat genus and 6 frugivorous bat species. Certain bat species widespread across Africa had serologic evidence of Zaire and Sudan Ebola viruses. No viral RNA was detected in the subset of samples tested (n = 665). Ongoing surveillance of bats and other potential animal reservoirs are required to predict and prepare for future outbreaks.

Lack of serological and molecular evidence of arbovirus infections in bats from Brazil.

Viruses are important agents of emerging zoonoses and are a substantial public health issue. Among emerging viruses, an important group are arboviruses, which are characterized by being maintained in nature in cycles involving hematophagous arthropod vectors and a wide range of vertebrate hosts. Recently, bats have received increasing attention as an important source for the emergence of zoonoses and as possible viral reservoirs. Among the arboviruses, there are many representatives of the genera Flavivirus and Alphavirus, which are responsible for important epidemics such as Dengue virus, Zika virus and Chikungunya virus. Due to the importance of analyzing potential viral reservoirs for zoonosis control and expanding our knowledge of bat viruses, this study aimed to investigate the presence of viruses of the Alphavirus and Flavivirus genera in bats. We analyzed serum, liver, lungs and intestine from 103 bats sampled in northeast and southern Brazil via Nested-PCR and the hemagglutination inhibition test. All samples tested in this study were negative for arboviruses, suggesting that no active or past infection was present in the captured bats. These data indicate that the bats examined herein probably do not constitute a reservoir for these viruses in the studied areas. Further studies are needed to clarify the role of bats as reservoirs and sources of infection of these viral zoonoses.

Methylenecyclopropyl glycine, not pesticide exposure as the primary etiological factor underlying hypoglycemic encephalopathy in Muzaffarpur, India

Some districts of Bihar, especially Muzzaffarpur district, have been known to be affected by annual outbreak, called locally as Acute Encephalitis Syndrome (AES) which became one of the major health concerns in Bihar, due to its high fatality and complications. Several hypotheses like bat virus, heat stroke, pesticide exposure and the presence of a compound – methylenecyclopropyl glycine (MCPG) in Litchi have been proposed by different investigators for AES. When the investigators examined the symptoms, signs and the epidemiological data, bat virus and heat stroke hypothesis were ruled out. Two major hypotheses which remain in question were the exposure to pesticides or MCPG present in litchi. Therefore, this study was designed to check the presence of both in the Muzzaffarpur samples of ripe and semi ripe litchi fruits. The fruit cover of ripe and semi ripe litchi showed the traces of Malathion (0.18-0.19 μg/g) and p’-p’-DDT (0.022–0.023 μg/g), while no pesticide residues were detected in the pulp of ripe or semi ripe litchi thereby ruling out the possibility of pesticide exposure in children of Muzzaffarpur. However, MCPG was detected in the pulp of semi ripe (0.57 μg/g) and ripe litchi fruits (0.19 μg/g). Further, when the human condition was simulated in animals, there was deprivation in body weight and glucose levels in starved litchi seed dosed rats, causing hypoglycemia. These results suggest that the cause of hypoglycemic encephalopathy in Muzzaffarpur is related to the consumption of semi ripe and ripe litchi fruits by undernourished children.

The complete genomic sequence of Rhinolophus gammaherpesvirus 1 isolated from a greater horseshoe bat.

In a comprehensive research project on bat viruses, we successfully isolated a novel herpesvirus from the spleen of a greater horseshoe bat (Rhinolophus ferrumequinum) in Japan using a cell line established from the kidney of the same bat. This herpesvirus was a novel gammaherpesvirus (Rhinolophus gammaherpesvirus 1; RGHV-1), which belonged to the genus Percavirus. The whole RGHV-1 genome (147,790 bp) showed that 12 of the 84 genes predicted to contain open reading frames did not show any homology to those of other herpesviruses.

Molecular and serological survey of lyssaviruses in Croatian bat populations

BackgroundRabies is the only known zoonotic disease of bat origin in Europe. The disease is caused by species belonging to the genus Lyssavirus. Five Lyssavirus species, i.e., European bat lyssavirus (EBLV)-1, EBLV-2, Bokeloh bat lyssavirus, Lleida bat lyssavirus, and West Caucasian bat virus, have been identified in European bats. More recently, a proposed sixth species, Kotalahti bat lyssavirus, was detected. Thus, in this study, active surveillance was initiated in order to obtain insights into the prevalence of lyssaviruses in Croatian bat populations and to improve our understanding of the public health threat of infected bats.ResultsIn total, 455 bats were caught throughout Continental and Mediterranean Croatia. Antibodies were found in 20 of 350 bats (5.71%, 95% confidence interval 3.73–8.66). The majority of seropositive bats were found in Trbušnjak cave (Continental Croatia, Eastern part), and most seropositive bats belonged to Myotis myotis (13/20). All oropharyngeal swabs were negative for the presence of Lyssavirus.ConclusionsThe presence of lyssaviruses in bat populations was confirmed for the first time in Croatia and Southeastern Europe. The results of this study suggest the need for further comprehensive analyses of lyssaviruses in bats in this part of Europe.

Novel Flu Viruses in Bats and Cattle: "Pushing the Envelope" of Influenza Infection.

Influenza viruses are among the major infectious disease threats of animal and human health. This review examines the recent discovery of novel influenza viruses in bats and cattle, the evolving complexity of influenza virus host range including the ability to cross species barriers and geographic boundaries, and implications to animal and human health.

Screening for viral proteins to some emerging viruses in African straw-coloured fruit bats (Eidolon Helvum) captured in Zaria, Nigeria

Background: Africa as a continent has recently experienced various zoonoses. Bats are indispensable reservoirs for the spread of emerging infectious diseases; African Straw-coloured Fruit bats (Eidolon helvum) are known for their migratory nature, going as far as 2000 km and have been linked to numerous viral diseases that affect both man and animals. This study was carried out to screen for the presence antibodies to Nipah virus soluble G protein (NiV sG), Nipah virus N protein (NiV N), Nipah virus soluble F protein (NiV sF), Hendra virus soluble G protein (HeV sG), Zaire Ebola virus G protein (EboV G), Cedar virus soluble G protein (CedV sG) and Menangle virus N protein (MenV N) in Eidolon helvum captured in Zaria, Nigeria. Methods & Materials: A total of forty-five (45) bats were trapped and captured from two residential bat roosts in Zaria. Bats were slaughtered for consumption with whole blood spotted on Whatman FTA cards and transported to CSIRO, Australia for screening by Luminex binding assay. Results: The result revealed low Median Fluorescent Intensity values for most samples but high values were obtained for HeV sG (2.2%) and MenV N (6.7%): this is suggestive of the presence of antibodies to these viruses. Conclusion: There are no evidences of NiV sG, NiV N, NiV sF, HeVsG, EboV G, CedV sG and MenV N proteins in bats in Zaria. Further investigation may recognize novel viruses of public health importance.

Maternal antibody and the maintenance of a lyssavirus in populations of seasonally breeding African bats.

Pathogens causing acute disease and death or lasting immunity require specific spatial or temporal processes to persist in populations. Host traits, such as maternally-derived antibody (MDA) and seasonal birthing affect infection maintenance within populations. Our study objective is to understand how viral and host traits lead to population level infection persistence when the infection can be fatal. We collected data on African fruit bats and a rabies-related virus, Lagos bat virus (LBV), including through captive studies. We incorporate these data into a mechanistic model of LBV transmission to determine how host traits, including MDA and seasonal birthing, and viral traits, such as incubation periods, interact to allow fatal viruses to persist within bat populations. Captive bat studies supported MDA presence estimated from field data. Captive bat infection-derived antibody decayed more slowly than MDA, and while faster than estimates from the field, supports field data that suggest antibody persistence may be lifelong. Unobserved parameters were estimated by particle filtering and suggest only a small proportion of bats die of disease. Pathogen persistence in the population is sensitive to this proportion, along with MDA duration and incubation period. Our analyses suggest MDA produced bats and prolonged virus incubation periods allow viral maintenance in adverse conditions, such as a lethal pathogen or strongly seasonal resource availability for the pathogen in the form of seasonally pulsed birthing.