A comparison of the diseases caused by Ross River virus and Barmah Forest virus

Exploring Barmah Forest virus pathogenesis: molecular tools to investigate non-structural protein 3 nuclear localization and viral genomic determinants of replication

Barmah Forest virus (BFV) is a mosquito-borne virus that causes arthralgia with accompanying rash, fever, and myalgia in humans. The virus is mainly found in Australia and has caused outbreaks associated with significant health concerns. As the sole representative of the Barmah Forest complex within the genus Alphavirus, BFV is not closely related genetically to other alphaviruses. Notably, basic knowledge of BFV molecular virology has not been well studied due to a lack of critical investigative tools such as an infectious clone. Here we describe the construction of an infectious BFV cDNA clone based on Genbank sequence and demonstrate that the clone-derived virus has in vitro and in vivo properties similar to naturally occurring virus, BFV field isolate 2193 (BFV2193-FI). A substitution in nsP4, V1911D, which was identified in the Genbank reference sequence, was found to inhibit virus rescue and replication. T1325P substitution in nsP2 selected during virus passaging was shown to be an adaptive mutation, compensating for the inhibitory effect of nsP4-V1911D. The two mutations were associated with changes in viral non-structural polyprotein processing and type I interferon (IFN) induction. Interestingly, a nuclear localization signal, active in mammalian but not mosquito cells, was identified in nsP3. A point mutation abolishing nsP3 nuclear localization attenuated BFV replication. This effect was more prominent in the presence of type I interferon signaling, suggesting nsP3 nuclear localization might be associated with IFN antagonism. Furthermore, abolishing nsP3 nuclear localization reduced virus replication in mice but did not significantly affect disease.IMPORTANCEBarmah Forest virus (BFV) is Australia's second most prevalent arbovirus, with approximately 1,000 cases reported annually. The clinical symptoms of BFV infection include rash, polyarthritis, arthralgia, and myalgia. As BFV is not closely related to other pathogenic alphaviruses or well-studied model viruses, our understanding of its molecular virology and mechanisms of pathogenesis is limited. There is also a lack of molecular tools essential for corresponding studies. Here we describe the construction of an infectious clone of BFV, variants harboring point mutations, and sequences encoding marker protein. In infected mammalian cells, nsP3 of BFV was located in the nuclei. This finding extends our understanding of the diverse mechanisms used by alphavirus replicase proteins to interact with host cells. Our novel observations highlight the complex synergy through which the viral replication machinery evolves to correct mutation errors within the viral genome.

Arbovirus Transmission in Australia from 2002 to 2017

Arboviruses pose a significant global public health threat, with Ross River virus (RRV), Barmah Forest virus (BFV), and dengue virus (DENV) being among the most common and clinically significant in Australia. Some arboviruses, including those prevalent in Australia, have been reported to cause transfusion-transmitted infections. This study examined the spatiotemporal variation of these arboviruses and their potential impact on blood donation numbers across Australia. Using data from the Australian Department of Health on eight arboviruses from 2002 to 2017, we retrospectively assessed the distribution and clustering of incidence rates in space and time using Geographic Information System mapping and space-time scan statistics. Regression models were used to investigate how weather variables, their lag months, space, and time affect case and blood donation counts. The predictors' importance varied with the spatial scale of analysis. Key predictors were average rainfall, minimum temperature, daily temperature variation, and relative humidity. Blood donation number was significantly associated with the incidence rate of all viruses and its interaction with local transmission of DENV, overall. This study, the first to cover eight clinically relevant arboviruses at a fine geographical level in Australia, identifies regions at risk for transmission and provides valuable insights for public health intervention.

Potential Serological Misdiagnosis of Barmah Forest Virus and Ross River Virus Diseases as Chikungunya Virus Infections in Australia: Comparison of ELISA with Neutralization Assay Results

To evaluate the frequency of errors in the diagnosis of medical laboratory-diagnosed Chikungunya virus (CHIKV) infections in Australia, we studied 42 laboratory-diagnosed CHIKV serum samples from one Queensland medical laboratory by ELISA IgG/IgM and measured the specific neutralization antibodies (Nab) against Barmah Forest virus (BFV), CHIKV and Ross River virus (RRV). The sero-positivity rates for the sera were as follows: anti-BFV IgG+ 19% (8/42), IgM+ 2.4% (1/42) and Nab+ 16.7% (7/42); anti-CHIKV IgG+ 90.5% (38/42), IgM+ 21.4% (9/42) and Nab+ 90.5% (38/42); anti-RRV IgG+ 88.1% (37/42), IgM+ 28.6% (12/42) and Nab+ 83.2% (35/42), respectively. Among the samples with multiple antibody positivity, 2.4% (1/42) showed triple ELISA IgM+, and 14.3% (6/42) exhibited double IgM RRV+CHIKV+; 9.5% (4/42) showed triple IgG+, 76.2% (32/42) displayed double IgG RRV+CHIKV+, 4.8% (2/42) showed IgG BFV+RRV+ and 4.8% (2/42) showed IgG BFV++CHIKV+; and 9.5% (4/42) showed triple Nab+ and 69% (29/42) exhibited double Nab RRV+CHIKV+, respectively. Our analysis of the single-virus infection control Nab results suggested no cross-neutralization between RRV and BFV, and only mild cross-neutralization between CHIKV and RRV, BFV and CHIKV, all with a ≥4-fold Nab titre ratio difference between the true virus infection and cross-reactivity counterpart virus. Subsequently, we re-diagnosed these 42 patients as 1 BFV+, 8 CHIKV+ and 23 RRV+ single-virus infections, along with five RRV+/BFV+ and four RRV+/CHIKV+ double infections, and one possible RRV+/BFV+ or RRV+CHIKV+, respectively. These findings suggests that a substantial proportion of medically attended RRV and BFV infections were misdiagnosed as CHIKV infections, highlighting the imperative need for diagnostic laboratory tests capable of distinguishing between CHIKV infections and actively co-circulating RRV and BFV. For a correct diagnosis, it is crucial to consider reliable diagnostic methods such as the neutralization assay to exclude RRV and BFV.

Genomic Analysis of Sindbis Virus Reveals Uncharacterized Diversity within the Australasian Region, and Support for Revised SINV Taxonomy

Sindbis virus (SINV) is a widely dispersed mosquito-borne alphavirus. Reports of Sindbis disease are largely restricted to northern Europe and South Africa. SINV is frequently sampled in Australian mosquito-based arbovirus surveillance programs, but human disease has rarely been reported. Molecular epidemiological studies have characterized six SINV genotypes (G1-G6) based on E2 gene phylogenies, mostly comprising viruses derived from the African-European zoogeographical region and with limited representation of Australasian SINV. In this study, we conducted whole genome sequencing of 66 SINV isolates sampled between 1960 and 2014 from countries of the Australasian region: Australia, Malaysia, and Papua New Guinea. G2 viruses were the most frequently and widely sampled, with three distinct sub-lineages defined. No new G6 SINV were identified, confirming geographic restriction of these viruses to south-western Australia. Comparison with global SINV characterized large-scale nucleotide and amino acid sequence divergence between African-European G1 viruses and viruses that circulate in Australasia (G2 and G3) of up to 26.83% and 14.55%, respectively, divergence that is sufficient for G2/G3 species demarcation. We propose G2 and G3 are collectively a single distinct alphavirus species that we name Argyle virus, supported by the inapparent or mild disease phenotype and the higher evolutionary rate compared with G1. Similarly, we propose G6, with 24.7% and 12.61% nucleotide and amino acid sequence divergence, is a distinct alphavirus species that we name Thomson's Lake virus.

Fine-scale genomic tracking of Ross River virus using nanopore sequencing

BACKGROUND

Ross River virus (RRV) is Australia's most common and widespread mosquito-transmitted arbovirus and is of significant public health concern. With increasing anthropogenic impacts on wildlife and mosquito populations, it is important that we understand how RRV circulates in its endemic hotspots to determine where public health efforts should be directed. Current surveillance methods are effective in locating the virus but do not provide data on the circulation of the virus and its strains within the environment. This study examined the ability to identify single nucleotide polymorphisms (SNPs) within the variable E2/E3 region by generating full-length haplotypes from a range of mosquito trap-derived samples.

METHODS

A novel tiled primer amplification workflow for amplifying RRV was developed with analysis using Oxford Nanopore Technology's MinION and a custom ARTIC/InterARTIC bioinformatic protocol. By creating a range of amplicons across the whole genome, fine-scale SNP analysis was enabled by specifically targeting the variable region that was amplified as a single fragment and established haplotypes that informed spatial-temporal variation of RRV in the study site in Victoria.

RESULTS

A bioinformatic and laboratory pipeline was successfully designed and implemented on mosquito whole trap homogenates. Resulting data showed that genotyping could be conducted in real time and that whole trap consensus of the viruses (with major SNPs) could be determined in a timely manner. Minor variants were successfully detected from the variable E2/E3 region of RRV, which allowed haplotype determination within complex mosquito homogenate samples.

CONCLUSIONS

The novel bioinformatic and wet laboratory methods developed here will enable fast detection and characterisation of RRV isolates. The concepts presented in this body of work are transferable to other viruses that exist as quasispecies in samples. The ability to detect minor SNPs, and thus haplotype strains, is critically important for understanding the epidemiology of viruses their natural environment.

Associations between temperature and Ross river virus infection: A systematic review and meta-analysis of epidemiological evidence

Ross River virus (RRV) infection is one of the emerging and prevalent arboviral diseases in Australia and the Pacific Islands. Although many studies have been conducted to establish the relationship between temperature and RRV infection, there has been no comprehensive review of the association so far. In this study, we performed a systematic review and meta-analysis to assess the effect of temperature on RRV transmission. We searched PubMed, Scopus, Embase, and Web of Science with additional lateral searches from references. The quality and strength of evidence from the included studies were evaluated following the Navigation Guide framework. We have qualitatively synthesized the evidence and conducted a meta-analysis to pool the relative risks (RRs) of RRV infection per 1 °C increase in temperature. Subgroup analyses were performed by climate zones, temperature metrics, and lag periods. A total of 17 studies met the inclusion criteria, of which six were included in the meta-analysis The meta-analysis revealed that the overall RR for the association between temperature and the risk of RRV infection was 1.09 (95% confidence interval (CI): 1.02, 1.17). Subgroup analyses by climate zones showed an increase in RRV infection per 1 °C increase in temperature in humid subtropical and cold semi-arid climate zones. The overall quality of evidence was "moderate" and we rated the strength of evidence to be "limited", warranting additional evidence to reduce uncertainty. The results showed that the risk of RRV infection is positively associated with temperature. However, the risk varies across different climate zones, temperature metrics and lag periods. These findings indicate that future studies on the association between temperature and RRV infection should consider local and regional climate, socio-demographic, and environmental factors to explore vulnerability at local and regional levels.

Impact of COVID-19 Mitigation Measures on Mosquito-Borne Diseases in 2020 in Queensland, Australia

We describe the impact of COVID-19 mitigation measures on mosquito-borne diseases in Queensland, Australia, during the first half of 2020. Implementation of restrictions coincided with an atypical late season outbreak of Ross River virus (RRV) characterized by a peak in notifications in April (1173) and May (955) which were greater than 3-fold the mean observed for the previous four years. We propose that limitations on human movement likely resulted in the majority of RRV infections being acquired at or near the place of residence, and that an increase in outdoor activities, such as gardening and bushwalking in the local household vicinity, increased risk of exposure to RRV-infected mosquitoes. In contrast, the precipitous decline in international passenger flights led to a reduction in the number of imported dengue and malaria cases of over 70% and 60%, respectively, compared with the previous five years. This substantial reduction in flights also reduced a risk pathway for importation of exotic mosquitoes, but the risk posed by importation via sea cargo was not affected. Overall, the emergence of COVID-19 has had a varied impact on mosquito-borne disease epidemiology in Queensland, but the need for mosquito surveillance and control, together with encouragement of personal protective measures, remains unchanged.

Imported arboviral infections in New Zealand, 2001 to 2017: A risk factor for local transmission

BACKGROUND/AIMS

Over the last decade and following international trends, cases of mosquito-borne arboviral infections, notably dengue fever, chikungunya and Zika, have increased among travellers arriving in New Zealand, but no locally acquired cases have been identified. Imported cases are characterised and examined to identify trends and features that might assist in reducing transmission risk from travellers.

METHODS

Information on traveller arrivals, notified cases and risk factors for disease acquisition were obtained from national sources. Trends in importation rates, seasonality are described and relationships of notifications with traveller arrivals were examined with a negative binomial regression model.

RESULTS

There was a significant increase in dengue notifications combined with the emergence of Zika and chikungunya. Most notifications were from arrivals in Auckland from Pacific Islands during summer and early autumn.

CONCLUSION/IMPLICATIONS

Overseas travel from New Zealand, particularly to the Pacific Islands and Southeast Asia, involves a risk of arboviral infection. The repeated introduction of arboviruses to New Zealand also increases the risk of local transmission in a country that has vector capable and vector potential mosquitoes, as well as an increasingly suitable climate for new vectors to establish.

Mosquito-Borne Viruses and Non-Human Vertebrates in Australia: A Review

Mosquito-borne viruses are well recognized as a global public health burden amongst humans, but the effects on non-human vertebrates is rarely reported. Australia, houses a number of endemic mosquito-borne viruses, such as Ross River virus, Barmah Forest virus, and Murray Valley encephalitis virus. In this review, we synthesize the current state of mosquito-borne viruses impacting non-human vertebrates in Australia, including diseases that could be introduced due to local mosquito distribution. Given the unique island biogeography of Australia and the endemism of vertebrate species (including macropods and monotremes), Australia is highly susceptible to foreign mosquito species becoming established, and mosquito-borne viruses becoming endemic alongside novel reservoirs. For each virus, we summarize the known geographic distribution, mosquito vectors, vertebrate hosts, clinical signs and treatments, and highlight the importance of including non-human vertebrates in the assessment of future disease outbreaks. The mosquito-borne viruses discussed can impact wildlife, livestock, and companion animals, causing significant changes to Australian ecology and economy. The complex nature of mosquito-borne disease, and challenges in assessing the impacts to non-human vertebrate species, makes this an important topic to periodically review.

Arthritogenic alphaviruses: epidemiological and clinical perspective on emerging arboviruses

Mosquito-borne viruses, or arboviruses, have been part of the infectious disease landscape for centuries, and are often, but not exclusively, endemic to equatorial and subtropical regions of the world. The past two decades saw the re-emergence of arthritogenic alphaviruses, a genus of arboviruses that includes several members that cause severe arthritic disease. Recent outbreaks further highlight the substantial public health burden caused by these viruses. Arthritogenic alphaviruses are often reported in the context of focused outbreaks in specific regions (eg, Caribbean, southeast Asia, and Indian Ocean) and cause debilitating acute disease that can extend to chronic manifestations for years after infection. These viruses are classified among several antigenic complexes, span a range of hosts and mosquito vectors, and can be distributed along specific geographical locations. In this Review, we highlight key features of alphaviruses that are known to cause arthritic disease in humans and outline the present findings pertaining to classification, immunogenicity, pathogenesis, and experimental approaches aimed at limiting disease manifestations. Although the most prominent alphavirus outbreaks in the past 15 years featured chikungunya virus, and a large body of work has been dedicated to understanding chikungunya disease mechanisms, this Review will instead focus on other arthritogenic alphaviruses that have been identified globally and provide a comprehensive appraisal of present and future research directions.

Epidemic Alphaviruses: Ecology, Emergence and Outbreaks

Over the past century, the emergence/reemergence of arthropod-borne zoonotic agents has been a growing public health concern. In particular, agents from the genus Alphavirus pose a significant risk to both animal and human health. Human alphaviral disease presents with either arthritogenic or encephalitic manifestations and is associated with significant morbidity and/or mortality. Unfortunately, there are presently no vaccines or antiviral measures approved for human use. The present review examines the ecology, epidemiology, disease, past outbreaks, and potential to cause contemporary outbreaks for several alphavirus pathogens.

Phylogenetic and Timescale Analysis of Barmah Forest Virus as Inferred from Genome Sequence Analysis

Barmah Forest virus (BFV) is a medically important mosquito-borne alphavirus endemic to Australia. Symptomatic disease can be a major cause of morbidity, associated with fever, rash, and debilitating arthralgia. BFV disease is similar to that caused by Ross River virus (RRV), the other major Australian alphavirus. Currently, just four BFV whole-genome sequences are available with no genome-scale phylogeny in existence to robustly characterise genetic diversity. Thirty novel genome sequences were derived for this study, for a final 34-taxon dataset sampled over a 44 year period. Three distinct BFV genotypes were characterised (G1-3) that have circulated in Australia and Papua New Guinea (PNG). Evidence of spatio-temporal co-circulation of G2 and G3 within regions of Australia was noted, including in the South West region of Western Australia (WA) during the first reported disease outbreaks in the state's history. Compared with RRV, the BFV population appeared more stable with less frequent emergence of novel lineages. Preliminary in vitro assessment of RRV and BFV replication kinetics found that RRV replicates at a significantly faster rate and to a higher, more persistent titre compared with BFV, perhaps indicating mosquitoes may be infectious with RRV for longer than with BFV. This investigation resolved a greater diversity of BFV, and a greater understanding of the evolutionary dynamics and history was attained.

Human monoclonal antibodies against Ross River virus target epitopes within the E2 protein and protect against disease

Ross River fever is a mosquito-transmitted viral disease that is endemic to Australia and the surrounding Pacific Islands. Ross River virus (RRV) belongs to the arthritogenic group of alphaviruses, which largely cause disease characterized by debilitating polyarthritis, rash, and fever. There is no specific treatment or licensed vaccine available, and the mechanisms of protective humoral immunity in humans are poorly understood. Here, we describe naturally occurring human mAbs specific to RRV, isolated from subjects with a prior natural infection. These mAbs potently neutralize RRV infectivity in cell culture and block infection through multiple mechanisms, including prevention of viral attachment, entry, and fusion. Some of the most potently neutralizing mAbs inhibited binding of RRV to Mxra8, a recently discovered alpahvirus receptor. Epitope mapping studies identified the A and B domains of the RRV E2 protein as the major antigenic sites for the human neutralizing antibody response. In experiments in mice, these mAbs were protective against cinical disease and reduced viral burden in multiple tissues, suggesting a potential therapeutic use for humans.

Epidemiologic, Entomologic, and Virologic Factors of the 2014-15 Ross River Virus Outbreak, Queensland, Australia

Australia experienced its largest recorded outbreak of Ross River virus (RRV) during the 2014-15 reporting year, comprising >10,000 reported cases. We investigated epidemiologic, entomologic, and virologic factors that potentially contributed to the scale of the outbreak in Queensland, the state with the highest number of notifications (6,371). Spatial analysis of human cases showed that notifications were geographically widespread. In Brisbane, human case notifications and virus detections in mosquitoes occurred across inland and coastal locations. Viral sequence data demonstrated 2 RRV lineages (northeastern genotypes I and II) were circulating, and a new strain containing 3 unique amino acid changes in the envelope 2 protein was identified. Longitudinal mosquito collections demonstrated unusually high relative abundance of Culex annulirostris and Aedes procax mosquitoes, attributable to extensive freshwater larval habitats caused by early and persistent rainfall during the reporting year. Increased prevalence of these mosquitoes probably contributed to the scale of this outbreak.

Flooding and Arboviral Disease: Predicting Ross River Virus Disease Outbreaks Across Inland Regions of South-Eastern Australia

Flood frequency is expected to increase across the globe with climate change. Understanding the relationship between flooding and arboviral disease can reduce disease risk and associated costs. South-eastern Australia is dominated by the flood-prone Murray-Darling River system where the incidence of Australia's most common arboviral disease, Ross River virus (RRV), is high. This study aimed to determine the relationship between riverine flooding and RRV disease outbreaks in inland south-eastern Australia, specifically New South Wales (NSW). Each study month from 1991 to 2013, for each of 37 local government areas (LGAs) was assigned 'outbreak/non-outbreak' status based on long-term trimmed-average age-standardized RRV notification rates and 'flood/non-flood' status based on riverine overflow. LGAs were grouped into eight climate zones with the relationship between flood and RRV outbreak modeled using generalized estimating equations. Modeling adjusted for rainfall in the previous 1-3 mo. Spring-summer flooding increased the odds of summer RRV outbreaks in three climate zones before and after adjusting for rainfall 1, 2, and 3 mo prior to the outbreak. Flooding at any time of the year was not predictive of RRV outbreaks in the remaining five climate zones. Predicting RRV disease outbreaks with flood events can assist with more targeted mosquito spraying programs, thereby reducing disease transmission and mosquito resistance.

Divergent Barmah Forest Virus from Papua New Guinea

We report a case of Barmah Forest virus infection in a child from Central Province, Papua New Guinea, who had no previous travel history. Genomic characterization of the virus showed divergent origin compared with viruses previously detected, supporting the hypothesis that the range of Barmah Forest virus extends beyond Australia.

Genome Sequences of Barmah Forest Virus Strains Isolated from Mosquitoes Trapped in Australian Defence Force Training Areas Reveal Multiple Nucleotide Insertions in the 3′ Untranslated Region

The complete genome sequences of two Barmah Forest virus (BFV) strains isolated from mosquitoes trapped in the Australian Defence Force (ADF) training areas during 2017 and 2018 reveal multiple nucleotide insertions in the 3′ untranslated region (UTR) of ADF BFV strains compared with the BFV prototype strain whole-genome sequence in GenBank.

The complete genome sequences of two Barmah Forest virus (BFV) strains isolated from mosquitoes trapped in the Australian Defence Force (ADF) training areas during 2017 and 2018 reveal multiple nucleotide insertions in the 3′ untranslated region (UTR) of ADF BFV strains compared with the BFV prototype strain whole-genome sequence in GenBank.

Flooding in Townsville, North Queensland, Australia, in February 2019 and Its Effects on Mosquito-Borne Diseases

In February 2019, a major flooding event occurred in Townsville, North Queensland, Australia. Here we present a prediction of the occurrence of mosquito-borne diseases (MBDs) after the flooding. We used a mathematical modelling approach based on mosquito population abundance, survival, and size as well as current infectiousness to predict the changes in the occurrences of MBDs due to flooding in the study area. Based on 2019 year-to-date number of notifiable MBDs, we predicted an increase in number of cases, with a peak at 104 by one-half month after the flood receded. The findings in this study indicate that Townsville may see an upsurge in the cases of MBDs in the coming days. However, the burden of diseases will go down again if the mosquito control program being implemented by the City Council continues. As our predictions focus on the near future, longer term effects of flooding on the occurrence of mosquito-borne diseases need to be studied further.

Ross River virus disease clinical presentation, pathogenesis and current therapeutic strategies

Ross River virus (RRV) is an arthitogenic alphavirus capable of causing outbreaks of debilitating musculoskeletal inflammatory disease in humans. RRV is the most common mosquito-borne disease in Australia, with outbreaks of RRV generally occurring during seasonal wet and warm conditions. Patients with Ross River virus disease (RRVD) typically present with fever, polyarthralgia, myalgia and a maculopapular erythematous rash. Treatment of the disease is usually palliative with no licensed vaccines or antiviral therapies currently available. In an effort to better inform therapeutic design, much progress has been made to understand the pathogenesis of RRVD. Progress has been largely driven by clinical evaluations supported by research using established murine models of RRVD, able to accurately replicate human disease. In this review we describe RRVD pathogenesis and the role of the host immune response, with particular focus on insights from studying animal models. We also discuss prospects for effective vaccines, preclinical development of therapeutic strategies and raise important questions for future RRV research.

Tropical arthritogenic alphaviruses

Tropical alphaviruses have special tropism for bone and joint tissue. Patients can develop chronic rheumatic disorders similar to rheumatoid arthritis and ankylosing spondylitis. The prototype is Chikungunya virus, although other lesser known viruses in our environment such as Sindbis, Ross River, Mayaro, O'nyong nyong and Barmah Forest viruses have the potential to be sped through vectors and cause chronic rheumatic disease. International population movements have increased the numbers of patients diagnosed with these tropical viruses in areas in which they are not endemic. Since they can leave persistent symptoms and affect the quality of life of the patients, it is important that we be aware of them. Changes in ecosystems have favored the expansion of competent mosquitoes, making fears of local transmission in southern Europe a reality. The objective of this review is to provide a clinical approach to the different arthritogenic tropical alphaviruses, especially those in which chronic rheumatic disease is more frequent.

A Survey of Knowledge, Attitudes, and Practices in Relation to Mosquitoes and Mosquito-Borne Disease in Western Australia

On average, more than 1,000 individuals will acquire a mosquito-borne disease in Western Australia (WA) each year. Knowledge, attitudes, and practices (KAP) in relation to mosquitoes and mosquito-borne disease have not yet been investigated within Australia. A randomized telephone survey of 2,500 households across 12 regions in WA was undertaken between February and May 2014. The aim of the survey was to obtain baseline KAP data surrounding mosquitoes and mosquito-borne diseases in different regions of WA, across a range of age groups and between males and females. The results of this survey indicate that the majority of respondents are aware of the potential for mosquitoes in WA to transmit Ross River virus, while awareness of other endemic mosquito-borne diseases remains limited. Common misconceptions exist in relation to exotic mosquito-borne diseases, with respondents incorrectly identifying malaria and dengue as endemic diseases in WA. The survey also highlighted a range of important issues, such as limited awareness of the potential for backyard breeding in domestic containers, occupational exposure to mosquitoes in regions with a large employment base in the mining and resources sector, increased exposure to mosquitoes as a result of participation in outdoor recreational activities in the north of the State, and reduced awareness of mosquito-borne disease in individuals aged 18-34 years. The results of this study will be used to inform the development of a new communication strategy by the Department of Health, to further raise awareness of mosquito-borne disease in WA. The data will then provide a baseline against which to compare future survey results, facilitating the rigorous evaluation of new communication efforts.

Investigation into High Barmah Forest Virus Disease Case Numbers Reported in the Northern Territory, Australia in 2012-2013

Between October 2012 and October 2013, unprecedented high numbers of Barmah Forest virus (BFV) disease cases were reported in the Northern Territory (NT). An investigation was launched by the NT Department of Health in cooperation with the Department of Primary Industry and Fisheries and the Department of Land Resource Management to investigate possible causes for this phenomenon. The investigation included virus isolations from mosquitoes collected in Darwin urban areas, BFV antibody testing in peri-urban small mammals and a human BFV disease case series investigation of recent cases. No BFV was isolated from the 4641 mosquitoes tested, none of the mammals tested positive for BFV antibodies, and the high BFV disease case numbers did not correlate with the relatively low mosquito vector numbers trapped in 2012-2013. It was estimated that up to 89% of the 79 human cases investigated did not have an acute arboviral illness and therefore had tested falsely positive. An Alere PanBio BFV immunoglobulin M enzyme-linked immunosorbent assay test kit is generally used to test for BFV, with the BFV disease case definition based on immunoglobulin M positives only. Other jurisdictions in Australia also reported high numbers of BFV disease cases, with the majority of the cases suspected to be false positives. Therefore, current testing methods need to be revised to reflect the true numbers of BFV disease cases occurring in Australia and to provide correct diagnoses for patients.

Ross River virus infection in a Thuringian traveller returning from south-east Australia

Ross River virus (RRV) is an arbovirus transmitted by Aedes and Culex mosquitos. It is endemic in Australia, New Zealand and south-east Asia. Clinical manifestation rates in adults range about 20-40%. Symptoms involve arthralgia, myalgia, lymphadenopathy, fever and rash. Here we report a case of RRV in a Thuringian traveller who visited the urban South-East of Australia.

Characterization of Barmah Forest virus pathogenesis in a mouse model

Alphaviruses including Barmah Forest virus (BFV) and Ross River virus (RRV) cause arthritis, arthralgia and myalgia in humans. The rheumatic symptoms in human BFV infection are very similar to those of RRV. Although RRV disease has been studied extensively, little is known about the pathogenesis of BFV infection. We sought to establish a mouse model for BFV to facilitate our understanding of BFV infectivity, tropism and pathogenesis, and to identify key pathological and immunological mechanisms of BFV infection that may distinguish between infections with BFV and RRV. Here, to the best of our knowledge, we report the first study assessing the virulence and replication of several BFV isolates in a mouse model. We infected newborn Swiss outbred mice with BFV and established that the BFV2193 prototype was the most virulent strain. BFV2193 infection resulted in the highest mortality among all BFV variant isolates, comparable to that of RRV. In comparison with RRV, C57BL/6 mice infected with BFV showed delayed onset, moderate disease scores and early recovery of the disease. BFV replicated poorly in muscle and did not cause the severe myositis seen in RRV-infected mice. The mRNAs for the inflammatory mediators TNF-α, IL-6, CCL2 and arginase-1 were highly upregulated in RRV- but not BFV-infected muscle. To our knowledge, this is the first report of a mouse model of BFV infection, which we have used to demonstrate differences between BFV and RRV infections and to further understand disease pathogenesis. With an increasing number of BFV cases occurring annually, a better understanding of the disease mechanisms is essential for future therapeutic development.

Molecular mechanisms involved in the pathogenesis of alphavirus-induced arthritis

Arthritogenic alphaviruses, including Ross River virus (RRV), Chikungunya virus (CHIKV), Sindbis virus (SINV), Mayaro virus (MAYV), O'nyong-nyong virus (ONNV), and Barmah Forest virus (BFV), cause incapacitating and long lasting articular disease/myalgia. Outbreaks of viral arthritis and the global distribution of these diseases point to the emergence of arthritogenic alphaviruses as an important public health problem. This review discusses the molecular mechanisms involved in alphavirus-induced arthritis, exploring the recent data obtained with in vitro systems and in vivo studies using animal models and samples from patients. The factors associated to the extension and persistence of symptoms are highlighted, focusing on (a) virus replication in target cells, and tissues, including macrophages and muscle cells; (b) the inflammatory and immune responses with recruitment and activation of macrophage, NK cells and T lymphocytes to the lesion focus and the increase of inflammatory mediators levels; and (c) the persistence of virus or viral products in joint and muscle tissues. We also discuss the importance of the establishment of novel animal models to test new molecular targets and to develop more efficient and selective drugs to treat these diseases.

Diagnosis of Barmah Forest virus infection by a nested real-time SYBR green RT-PCR assay

Barmah Forest virus (BFV) is a mosquito borne (+) ssRNA alphavirus found only in Australia. It causes rash, myalgia and arthralgia in humans and is usually diagnosed serologically. We developed a real-time PCR assay to detect BFV in an effort to improve diagnosis early in the course of infection. The limit of detection was 16 genome equivalents with a specificity of 100%. Fifty five serum samples from BFV-infected patients were tested by the PCR. 52 of 53 antibody-positive samples were PCR negative. Two culture-positive (neutralizing antibody negative) samples were positive on first round PCR, while one sample (IgM and neutralizing antibody strongly positive, IgG negative) was positive on second round PCR, suggesting that viral RNA is detectable and transiently present in early infection. PCR can provide results faster than culture, is capable of high throughput and by sequencing the PCR product strain variants can be characterized.

Surveillance should be strengthened to improve epidemiological understandings of mosquito-borne Barmah Forest virus infection

INTRODUCTION

Barmah Forest virus (BFV) is a mosquito-borne virus causing epidemic polyarthritis in Australia. This study used case follow-up of cases from the surveillance system to demonstrate that routinely collected BFV notification data were an unreliable indicator of the true location of exposure.

METHODS

BFV notifications from June 2001 to May 2011 were extracted from the New South Wales (NSW) Notifiable Conditions Information Management System to study case distribution. Disease cluster analysis was performed using spatial scan statistics. Exposure history data were collected from cases notified in 2010 and 2011 to accurately determine travel to high-risk areas.

RESULTS

Cluster analysis using address data identified an area of increased BFV disease incidence in the mid-north coast of NSW contiguous with estuarine wetlands. When travel to this area was investigated, 96.7% (29/30) cases reported having visited coastal regions within four weeks of developing symptoms.

DISCUSSION

Along the central NSW coastline, extensive wetlands occur in close proximity to populated areas. These wetlands provide ideal breeding habitats for a range of mosquito species implicated in the transmission of BFV. This is the first study to fully assess case exposure with findings suggesting that sporadic cases of BFV in people living further away from the coast do not reflect alternative exposure sites but are likely to result from travel to coastal regions. Spatial analysis by case address alone may lead to inaccurate understandings of the true distribution of arboviral diseases. Subsequently, this information has important implications for the collection of mosquito-borne disease surveillance information and public health response strategies.

Arthritogenic alphaviruses--an overview

Mosquito-transmitted alphaviruses causing human rheumatic disease are globally distributed and include chikungunya virus, Ross River virus, Barmah Forest virus, Sindbis virus, o'nyong-nyong virus and Mayaro virus. These viruses cause endemic disease and, occasionally, large epidemics; for instance, the 2004-2011 chikungunya epidemic resulted in 1.4-6.5 million cases, with imported cases reported in nearly 40 countries. The disease is usually self-limiting and characterized by acute and chronic symmetrical peripheral polyarthralgia-polyarthritis, with acute disease usually including fever, myalgia and/or rash. Arthropathy can be debilitating, usually lasts weeks to months and can be protracted; although adequate attention to differential diagnoses is recommended. The latest chikungunya virus epidemic was also associated with some severe disease manifestations and mortality, primarily in elderly patients with comorbidities and the young. Chronic alphaviral rheumatic disease probably arises from inflammatory responses stimulated by the virus persisting in joint tissues, despite robust antiviral immune responses. Serodiagnosis by ELISA is the standard; although international standardization is often lacking. Treatment usually involves simple analgesics and/or NSAIDs, which can provide relief, but better drug treatments are clearly needed. However, the small market size and/or the unpredictable and rapid nature of epidemics present major hurdles for development and deployment of new alphavirus-specific interventions.

Spatio-temporal patterns of Barmah Forest virus disease in Queensland, Australia

Background

Barmah Forest virus (BFV) disease is a common and wide-spread mosquito-borne disease in Australia. This study investigated the spatio-temporal patterns of BFV disease in Queensland, Australia using geographical information system (GIS) tools and geostatistical analysis.

Methods/Principal Findings

We calculated the incidence rates and standardised incidence rates of BFV disease. Moran's I statistic was used to assess the spatial autocorrelation of BFV incidences. Spatial dynamics of BFV disease was examined using semi-variogram analysis. Interpolation techniques were applied to visualise and display the spatial distribution of BFV disease in statistical local areas (SLAs) throughout Queensland. Mapping of BFV disease by SLAs reveals the presence of substantial spatio-temporal variation over time. Statistically significant differences in BFV incidence rates were identified among age groups (χ² = 7587, df = 7327,p<0.01). There was a significant positive spatial autocorrelation of BFV incidence for all four periods, with the Moran's I statistic ranging from 0.1506 to 0.2901 (p<0.01). Semi-variogram analysis and smoothed maps created from interpolation techniques indicate that the pattern of spatial autocorrelation was not homogeneous across the state.

Conclusions/Significance

This is the first study to examine spatial and temporal variation in the incidence rates of BFV disease across Queensland using GIS and geostatistics. The BFV transmission varied with age and gender, which may be due to exposure rates or behavioural risk factors. There are differences in the spatio-temporal patterns of BFV disease which may be related to local socio-ecological and environmental factors. These research findings may have implications in the BFV disease control and prevention programs in Queensland.

Host response to Chikungunya virus and perspectives for immune-based therapies

Chikungunya virus (CHIKV), a dormant ‘old world’ alphavirus, has warranted worldwide research attention due to the explosive nature of its outbreak events during 2004–2008. Despite being around for more than 50 years, CHIKV still remains elusive compared with other members of the alphavirus family. In light of the potential threat that CHIKV poses, encouraging efforts are taking place to understand CHIKV from different perspectives. This review summarizes our current clinical, pathological and immunological knowledge of CHIKV and examines how we can utilize our understanding of host response for therapeutic strategies.

Spatial-temporal epidemiological analyses of two sympatric, co-endemic alphaviral diseases in Queensland, Australia

BACKGROUND

The two most reported mosquito-borne diseases in Queensland, a northern state of Australia, are Ross River virus (RRV) disease and Barmah Forest virus (BFV) disease. Both diseases are endemic in Queensland and have similar clinical symptoms and comparable transmission cycles involving a complex inter-relationship between human hosts, various mosquito vectors, and a range of nonhuman vertebrate hosts, including marsupial mammals that are unique to the Australasian region. Although these viruses are thought to share similar vectors and vertebrate hosts, RRV is four times more prevalent than BFV in Queensland.

METHODS

We performed a retrospective analysis of BFV and RRV human disease notification data collected from 1995 to 2007 in Queensland to ascertain whether there were differences in the incidence patterns of RRV and BFV disease. In particular, we compared the temporal incidence and spatial distribution of both diseases and considered the relationship between their disease dynamics. We also investigated whether a peak in BFV incidence during spring was indicative of the following RRV and BFV transmission season incidence levels.

RESULTS

Although there were large differences in the notification rates of the two diseases, they had similar annual temporal patterns, but there were regional variations between the length and magnitude of the transmission seasons. During periods of increased disease activity, however, there was no association between the dynamics of the two diseases.

CONCLUSIONS

The results from this study suggest that while RRV and BFV share similar mosquito vectors, there are significant differences in the ecology of these viruses that result in different epidemic patterns of disease incidence. Further investigation is required into the ecology of each virus to determine which factors are important in promoting RRV and BFV disease outbreaks.

Arbovirus models to provide practical management tools for mosquito control and disease prevention in the Northern Territory, Australia

Ross River virus (RRV) causes the most common human arbovirus disease in Australia. Although the disease is nonfatal, the associated arthritis and postinfection fatigue can be debilitating for many months, impacting on workforce participation. We sought to create an early-warning system to notify of approaching RRV disease outbreak conditions for major townships in the Northern Territory. By applying a logistic regression model to meteorologic factors, including rainfall, a postestimation analysis of sensitivity and specificity can create rainfall cut-points. These rainfall cut-points indicate the rainfall level above which previous epidemic conditions have occurred. Furthermore, rainfall cut-points indirectly adjust for vertebrate host data from the agile wallaby (Macropus agilis) as the life cycle of the agile wallaby is intricately meshed with the wet season. Once generated, cut-points can thus be used prospectively to allow timely implementation of larval survey and control measures and public health warnings to preemptively reduce RRV disease incidence. Cut-points are location specific and have the capacity to replace previously used models, which require data management and input, and rarely provide timely notification for vector control requirements and public health warnings. These methods can be adapted for use elsewhere.

[Emerging viral infections in South East Asia and the Pacific region]

The epidemiology of several viral diseases underwent profound changes in South-East Asia and Oceania over the past decades. This was due to several factors, including the geographical distribution of vectors and the viruses they transmit; increasing traveling and trade; increasing ecological and demographic pressure. We reviewed the current state of knowledge based on published sources and available epidemiological data. The review was limited to potentially emerging viruses in Southeast Asia and the Pacific reported in human cases. Dengue, Chikungunya, and Japanese Encephalitis viruses have recurred on a yearly basis with a steady increase in these regions. Ross River and Barmah viruses now appear regularly in Australia, in an increasing number of cases. Nipah virus strikes regularly with limited but deadly epidemics in Southeast Asia. Finally, infections by lyssaviruses, Kunjin, Murray Valley, or Zika viruses were also reviewed.

Socio-environmental predictors of Barmah forest virus transmission in coastal areas, Queensland, Australia

OBJECTIVE

To assess the socio-environmental predictors of Barmah forest virus (BFV) transmission in coastal areas, Queensland, Australia.

METHODS

Data on BFV notified cases, climate, tidal levels and socioeconomic index for area (SEIFA) in six coastal cities, Queensland, for the period 1992-2001 were obtained from the relevant government agencies. Negative binomial regression models were used to assess the socio-environmental predictors of BFV transmission.

RESULTS

The results show that maximum and minimum temperature, rainfall, relative humidity, high and low tide were statistically significantly associated with BFV incidence at lags 0-2 months. The fitted negative binomial regression models indicate a significant independent association of each of maximum temperature (beta = 0.139, P = 0.000), high tide (beta = 0.005, P = 0.000) and SEIFA index (beta = -0.010, P = 0.000) with BFV transmission after adjustment for confounding variables.

CONCLUSIONS

The transmission of BFV disease in Queensland coastal areas seemed to be determined by a combination of local social and environmental factors. The model developed in this study may have applications in the control and prevention of BFV disease in these areas.

Ross River virus and Barmah Forest virus infections: a review of history, ecology, and predictive models, with implications for tropical northern Australia

The purpose of the present article is to present a review of the Ross River virus (RRV) and Barmah Forest virus (BFV) literature in relation to potential implications for future disease in tropical northern Australia. Ross River virus infection is the most common and most widespread arboviral disease in Australia, with an average of 4,800 national notifications annually. Of recent concern is the sudden rise in BFV infections; the 2005-2006 summer marked the largest BFV epidemic on record in Australia, with 1,895 notifications. Although not life-threatening, infection with either virus can cause arthritis, myalgia, and fatigue for 6 months or longer, resulting in substantial morbidity and economic impact. The geographic distribution of mosquito species and their seasonal activity is determined in large part by temperature and rainfall. Predictive models can be useful tools in providing early warning systems for epidemics of RRV and BFV infection. Various models have been developed to predict RRV outbreaks, but these appear to be mostly only regionally valid, being dependent on local ecological factors. Difficulties have arisen in developing useful models for the tropical northern parts of Australia, and to date no models have been developed for the Northern Territory. Only one model has been developed for predicting BFV infections using climate and tide variables. It is predicted that the exacerbation of current greenhouse conditions will result in longer periods of high mosquito activity in the tropical regions where RRV and BFV are already common. In addition, the endemic locations may expand further within temperate regions, and epidemics may become more frequent in those areas. Further development of predictive models should benefit public health planning by providing early warning systems of RRV and BFV infection outbreaks in different geographical locations.

Is New Zealand prepared to deal with arboviral diseases?

To now, New Zealand has been spared arboviral diseases, except for the odd imported infection. However, two exotic vector mosquitoes (Ochlerotatus camptorhynchus and Ochlerotatus notoscriptus) have become established in New Zealand and the routine arrival of infected people from overseas may soon lead to local arboviral transmission. Large populations of wild wallabies and Brushtail possums could serve as reservoirs of Ross River virus and other arboviruses. Several other exotic mosquito species, including important disease vectors such as Aedes albopictus and Aedes aegypti, have already been intercepted in New Zealand. It is clear that increased border surveillance is necessary if we are to interdict the establishment of such species. We recommend several measures that should be adopted, including increased training and awareness of public health officials, clinicians and the general public, and taking appropriate steps to make New Zealand self-sustainable in terms of arboviral surveillance, diagnosis, and prevention.

Viral exanthems in the tropics

Viral exanthems are a common problem in tropical regions, particularly affecting children. Most exanthems are transient and harmless, but some are potentially very dangerous. Pregnant women and malnourished or immunocompromised infants carry the greatest risk of adverse outcome. In this article, parvovirus B19; dengue and yellow fever; West Nile, Barmah Forest, Marburg, and Ebola viruses, and human herpesviruses; asymmetric periflexural exanthema of childhood; measles; rubella; enteroviruses; Lassa fever; and South American hemorrhagic fevers will be discussed.

Weather variability, tides, and Barmah Forest virus disease in the Gladstone region, Australia

In this study we examined the impact of weather variability and tides on the transmission of Barmah Forest virus (BFV) disease and developed a weather-based forecasting model for BFV disease in the Gladstone region, Australia. We used seasonal autoregressive integrated moving-average (SARIMA) models to determine the contribution of weather variables to BFV transmission after the time-series data of response and explanatory variables were made stationary through seasonal differencing. We obtained data on the monthly counts of BFV cases, weather variables (e.g., mean minimum and maximum temperature, total rainfall, and mean relative humidity), high and low tides, and the population size in the Gladstone region between January 1992 and December 2001 from the Queensland Department of Health, Australian Bureau of Meteorology, Queensland Department of Transport, and Australian Bureau of Statistics, respectively. The SARIMA model shows that the 5-month moving average of minimum temperature (b=0.15, p-value<0.001) was statistically significantly and positively associated with BFV disease, whereas high tide in the current month (b=-1.03, p-value=0.04) was statistically significantly and inversely associated with it. However, no significant association was found for other variables. These results may be applied to forecast the occurrence of BFV disease and to use public health resources in BFV control and prevention.

Viral Arthritis

The role of viruses in the development of acute and chronic arthritis is complex, because viruses are ubiquitous, and all human beings are occasionally afflicted by viral infections. In general, most viral infections are acute and self-limiting and survive by infecting one susceptible host, then moving on to another. Some viruses establish prolonged latency in the host after acute infection, whereas other agents produce chronic infections following the primary stage. The mechanisms whereby these infections produce arthritis are diverse and still poorly understood, but are clearly influenced by both host and viral factors. This review addresses these and other common forms of viral arthritis, such as that caused by parvovirus B19.

Ross River virus: Molecular and cellular aspects of disease pathogenesis

Ross River virus (RRV) is a mosquito-borne alphavirus indigenous to Australia and the Western Pacific region and is responsible for several thousand cases of human RRV disease (RRVD) per annum. The disease primarily involves polyarthritis/arthralgia, with many patients also presenting with rash, myalgia, fever, and/or lethargy. The symptoms can be debilitating at onset, but they usually resolve within 3-6 months. Recent insights into the RRV-host relationship, associated pathology, and molecular biology of infection have generated a number of potential avenues for improved treatment. Although vaccine development has been proposed, the small market size and potential for antibody-dependent enhancement (ADE) of disease make this approach unattractive. Recent insights into the molecular basis of RRV-ADE and the virus's ability to manipulate host inflammatory and immune responses create potential new opportunities for therapeutic invention. Such interventions should overcome virus-induced dysregulation of protective host responses to promote viral clearance and/or ameliorate inflammatory immunopathology.

An arthritogenic alphavirus uses the α1β1 integrin collagen receptor

Ross River (RR) virus is an alphavirus endemic to Australia and New Guinea and is the aetiological agent of epidemic polyarthritis or RR virus disease. Here we provide evidence that RR virus uses the collagen-binding alpha1beta1 integrin as a cellular receptor. Infection could be inhibited by collagen IV and antibodies specific for the beta1 and alpha1 integrin proteins, and fibroblasts from alpha1-integrin-/- mice were less efficiently infected than wild-type fibroblasts. Soluble alpha1beta1 integrin bound immobilized RR virus, and peptides representing the alpha1beta1 integrin binding-site on collagen IV inhibited virus binding to cells. We speculate that two highly conserved regions within the cell-receptor binding domain of E2 mimic collagen and provide access to cellular collagen-binding receptors.

El Niño Southern Oscillation and Ross River virus outbreaks in Australia

Various authors have suggested a general predictive value of climatic indices of El Niño/Southern Oscillation events as indicators of outbreaks of arbovirus disease, particularly Ross River virus in Australia. By analyzing over 100 years of historical outbreak data on Ross River virus disease, our data indicate that, although high Southern Oscillation Index and La Niña conditions are potentially important predictors for the Murray Darling River region, this is not the case for the other four ecological zones in Australia. Our study, therefore, cautions against overgeneralization and suggests that, since climate and weather exert different influences and have different biological implications for the multiplicity of vectors involved, it is logical that predictors should be heterogeneous.

Spatiotemporal variation of notified Barmah Forest virus infections in Queensland, Australia, 1993-2001

The spatiotemporal variations of Barmah Forest virus (BFv) infections were assessed in Queensland, Australia, between 1993 and 2001 utilizing a Geographic Information System. The notified BFv cases came from 441 localities between 1993 and 1995, 512 between 1996 and 1998, and 546 between 1999 and 2001. A statistically significant increase was observed in the number of localities from which the cases were notified by 16.1% for the period of 1996-1998 and 23.8% for 1999-2001, compared with that for 1993-1995 (chi2 (df=2) = 11.5; p < 0.01). These results indicate that there has been an expanded geographic distribution of the notified BFv infections in Queensland over the last decade. Socioecological changes may be causal factors in this expansion.