Ross River virus infection on the North Coast of New South Wales

Exposure dynamics of Ross River virus in horses - Horses as potential sentinels (a One Health approach)

Ross River virus (RRV), the most medically and economically important arbovirus in Australia, has been the most prevalent arbovirus infections in humans for many years. Infected humans and horses often suffer similar clinical symptoms. We conducted a prospective longitudinal study over a 3.5-year period to investigate the exposure dynamics of RRV in three foal cohorts (n = 32) born in a subtropical region of South East Queensland, Australia, between 2020 and 2022. RRV-specific seroconversion was detected in 56% (n = 18) of foals with a median time to seroconversion, after waning of maternal antibodies, of 429 days (95% CI: 294-582). The median age at seroconversion was 69 weeks (95% CI: 53-57). Seroconversion events were only detected between December and March (Southern Hemisphere summer) over the entire study period. Cox proportion hazards regression analyses revealed that seroconversions were significantly (p < 0.05) associated with air temperature in the month of seroconversion. Time-lags in meteorological variables were not significantly (p > 0.05) associated with seroconversion, except for relative humidity (p = 0.036 at 2-month time-lag). This is in contrast to research results of RRV infection in humans, which peaked between March and May (Autumn) and with a 0-3 month time-lag for various meteorological risk factors. Therefore, horses may be suitable sentinels for monitoring active arbovirus circulation and could be used for early arbovirus outbreak detection in human populations.

Testing the intrinsic mechanisms driving the dynamics of Ross River Virus across Australia

The mechanisms driving dynamics of many epidemiologically important mosquito-borne pathogens are complex, involving combinations of vector and host factors (e.g., species composition and life-history traits), and factors associated with transmission and reporting. Understanding which intrinsic mechanisms contribute most to observed disease dynamics is important, yet often poorly understood. Ross River virus (RRV) is Australia's most important mosquito-borne disease, with variable transmission dynamics across geographic regions. We used deterministic ordinary differential equation models to test mechanisms driving RRV dynamics across major epidemic centers in Brisbane, Darwin, Mandurah, Mildura, Gippsland, Renmark, Murray Bridge, and Coorong. We considered models with up to two vector species (Aedes vigilax, Culex annulirostris, Aedes camptorhynchus, Culex globocoxitus), two reservoir hosts (macropods, possums), seasonal transmission effects, and transmission parameters. We fit models against long-term RRV surveillance data (1991-2017) and used Akaike Information Criterion to select important mechanisms. The combination of two vector species, two reservoir hosts, and seasonal transmission effects explained RRV dynamics best across sites. Estimated vector-human transmission rate (average β = 8.04x10-4per vector per day) was similar despite different dynamics. Models estimate 43% underreporting of RRV infections. Findings enhance understanding of RRV transmission mechanisms, provide disease parameter estimates which can be used to guide future research into public health improvements and offer a basis to evaluate mitigation practices.

Ross River Virus Infection: A Cross-Disciplinary Review with a Veterinary Perspective

Ross River virus (RRV) has recently been suggested to be a potential emerging infectious disease worldwide. RRV infection remains the most common human arboviral disease in Australia, with a yearly estimated economic cost of $4.3 billion. Infection in humans and horses can cause chronic, long-term debilitating arthritogenic illnesses. However, current knowledge of immunopathogenesis remains to be elucidated and is mainly inferred from a murine model that only partially resembles clinical signs and pathology in human and horses. The epidemiology of RRV transmission is complex and multifactorial and is further complicated by climate change, making predictive models difficult to design. Establishing an equine model for RRV may allow better characterization of RRV disease pathogenesis and immunology in humans and horses, and could potentially be used for other infectious diseases. While there are no approved therapeutics or registered vaccines to treat or prevent RRV infection, clinical trials of various potential drugs and vaccines are currently underway. In the future, the RRV disease dynamic is likely to shift into temperate areas of Australia with longer active months of infection. Here, we (1) review the current knowledge of RRV infection, epidemiology, diagnostics, and therapeutics in both humans and horses; (2) identify and discuss major research gaps that warrant further research.

Ross River Virus Infection of Horses: Appraisal of Ecological and Clinical Consequences

Ross River virus (RRV) is a mosquito-borne arbovirus of the genus Alphavirus that causes disease in humans and horses in Australia. A temporal association of RRV infection in horses with clinical signs including pyrexia, malaise, and polyarthralgia has been reported, along with reduced athletic performance, often for extended periods. Despite these reports, disease due to RRV remains somewhat controversial as experimental infection of horses has resulted in obvious viraemia yet minimal signs of clinical disease. The relatively high viraemia demonstrated by horses infected with RRV has led to speculation that they could act as an important reservoir host of the virus, although this remains unclear. This review sought to appraise the existing literature relating to RRV infection of horses and to summarize the ecological and clinical consequences of RRV of relevance to the equine industry and to public health more broadly.

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.

Arthritogenic Alphaviruses: A Worldwide Emerging Threat?

Arthritogenic alphaviruses are responsible for a dengue-like syndrome associated with severe debilitating polyarthralgia that can persist for months or years and impact life quality. Chikungunya virus is the most well-known member of this family since it was responsible for two worldwide epidemics with millions of cases in the last 15 years. However, other arthritogenic alphaviruses that are as of yet restrained to specific territories are the cause of neglected tropical diseases: O'nyong'nyong virus in Sub-Saharan Africa, Mayaro virus in Latin America, and Ross River virus in Australia and the Pacific island countries and territories. This review evaluates their emerging potential in light of the current knowledge for each of them and in comparison to chikungunya virus.

Predictive modelling of Ross River virus notifications in southeastern Australia

Ross River virus (RRV) is a mosquito-borne virus endemic to Australia. The disease, marked by arthritis, myalgia and rash, has a complex epidemiology involving several mosquito species and wildlife reservoirs. Outbreak years coincide with climatic conditions conducive to mosquito population growth. We developed regression models for human RRV notifications in the Mildura Local Government Area, Victoria, Australia with the objective of increasing understanding of the relationships in this complex system, providing trigger points for intervention and developing a forecast model. Surveillance, climatic, environmental and entomological data for the period July 2000-June 2011 were used for model training then forecasts were validated for July 2011-June 2015. Rainfall and vapour pressure were the key factors for forecasting RRV notifications. Validation of models showed they predicted RRV counts with an accuracy of 81%. Two major RRV mosquito vectors (Culex annulirostris and Aedes camptorhynchus) were important in the final estimation model at proximal lags. The findings of this analysis advance understanding of the drivers of RRV in temperate climatic zones and the models will inform public health agencies of periods of increased risk.

Educational strategies for chronically ill students: Chronic Fatigue Syndrome

Chronic illness, such as Chronic Fatigue Syndrome, has a major impact on the sociol, emotional, and educational well-being of the young people affected by it. Many students are either absent from school for prolonged periods or able to attend for only a few classes each week. Students have identified the importance of educational strategies in the management of their illness. If the school or educational setting is functioning appropriately, then social, emotional, developmental, and academic issues associated with chronic illness gradually resolve. A program developed in conjunction with the Victorian Visiting Teacher Service is described. Strategies used to assist housebound students, their carers, teaching staff, and students who are gradually returning to school are outlined.

Analysis and prediction of Ross River virus transmission in New South Wales, Australia

BACKGROUND

Ross River virus (RRV) disease is the most widespread mosquito-borne disease in Australia. The disease is maintained in enzootic cycles between mosquitoes and reservoir hosts. During outbreaks and in endemic regions, RRV transmission can be sustained between vectors and reservoir hosts in zoonotic cycles with spillover to humans. Symptoms include arthritis, rash, fever and fatigue and can persist for several months. The prevalence and associated morbidity make this disease a medically and economically important mosquito-borne disease in Australia.

METHODS

Climate, environment, and RRV vector and reservoir host information were used to develop predictive models in four regions in NSW over a 13-year period (1991-2004). Polynomial distributed lag (PDL) models were used to explore long-term influences of up to 2 years ago that could be related to RRV activity.

RESULTS

Each regional model consisted of a unique combination of predictors for RRV disease highlighting the differences in the disease ecology and epidemiology in New South Wales (NSW). Events up to 2 years before were found to influence RRV activity. The shorter-term associations may reflect conditions that promote virus amplification in RRV vectors whereas long-term associations may reflect RRV reservoir host breeding and herd immunity. The models indicate an association between host populations and RRV disease, lagged by 24 months, suggesting two or more generations of susceptible juveniles may be necessary for an outbreak. Model sensitivities ranged from 60.4% to 73.1%, and model specificities ranged from 57.9% to 90.7%. This was the first study to include reservoir host data into statistical RRV models; the inclusion of host parameters was found to improve model fit significantly.

CONCLUSION

The research presents the novel use of a combination of climate, environment, and RRV vector and reservoir host information in statistical predictive models. The models have potential for public health decision-making.

Genetic ablation of arginase 1 in macrophages and neutrophils enhances clearance of an arthritogenic alphavirus

Chikungunya virus (CHIKV) and Ross River virus (RRV) cause a debilitating, and often chronic, musculoskeletal inflammatory disease in humans. Macrophages constitute the major inflammatory infiltrates in musculoskeletal tissues during these infections. However, the precise macrophage effector functions that affect the pathogenesis of arthritogenic alphaviruses have not been defined. We hypothesized that the severe damage to musculoskeletal tissues observed in RRV- or CHIKV-infected mice would promote a wound-healing response characterized by M2-like macrophages. Indeed, we found that RRV- and CHIKV-induced musculoskeletal inflammatory lesions, and macrophages present in these lesions, have a unique gene-expression pattern characterized by high expression of arginase 1 and Ym1/Chi3l3 in the absence of FIZZ1/Relmα that is consistent with an M2-like activation phenotype. Strikingly, mice specifically deleted for arginase 1 in neutrophils and macrophages had dramatically reduced viral loads and improved pathology in musculoskeletal tissues at late times post-RRV infection. These findings indicate that arthritogenic alphavirus infection drives a unique myeloid cell activation program in inflamed musculoskeletal tissues that inhibits virus clearance and impedes disease resolution in an arginase 1-dependent manner.

Post-epidemic Chikungunya disease on Reunion Island: course of rheumatic manifestations and associated factors over a 15-month period

Although the acute manifestations of Chikungunya virus (CHIKV) illness are well-documented, few data exist about the long-term rheumatic outcomes of CHIKV-infected patients. We undertook between June and September 2006 a retrospective cohort study aimed at assessing the course of late rheumatic manifestations and investigating potential risk factors associated with the persistence of these rheumatic manifestations over 15 months. 147 participants (>16 yrs) with laboratory-confirmed CHIKV disease diagnosed between March 1 and June 30, 2005, were identified through a surveillance database and interviewed by telephone. At the 15-month-period evaluation after diagnosis, 84 of 147 participants (57%) self-reported rheumatic symptoms. Of these 84 patients, 53 (63%) reported permanent trouble while 31 (37%) had recurrent symptoms. Age ≥45 years (OR = 3.9, 95% CI 1.7–9.7), severe initial joint pain (OR = 4.8, 95% CI 1.9–12.1), and presence of underlying osteoarthritis comorbidity (OR = 2.9, 95% CI 1.1–7.4) were predictors of nonrecovery. Our findings suggest that long-term CHIKV rheumatic manifestations seem to be a frequent underlying post-epidemic condition. Three independent risk factors that may aid in early recognition of patients with the highest risk of presenting prolonged CHIKV illness were identified. Such findings may be particularly useful in the development of future prevention and care strategies for this emerging virus infection.

Transmitted by day-biting mosquitoes, Chikungunya virus (CHIKV), causing febrile illness and joint pain, is widespread in Africa and Asia. Recent outbreaks in the Indian Ocean islands, its rapid expansion across continents, and its unusual clinical acute pattern have shed light on and brought awareness of this re-emerging virus. However, late rheumatic manifestations of this infection remain poorly examined. Thus, we have evaluated over a 15-month period the evolution and assessed potential risk factors of CHIKV-related rheumatic manifestations in a cohort of Reunion Island residents infected with CHIKV during the initial phase of the epidemic in 2005. Eligible adult patients were identified through a surveillance database. We found that rheumatic symptoms lasted for at least 15 months in 57% of the participants. Of these, 63% reported permanent trouble while 37% had recurrent symptoms. Factors such as age ≥45 years, severe initial joint pain, and presence of underlying osteoarthritis comorbidity were associated with nonrecovery over the 15-month period. Our findings suggest that long-term CHIKV rheumatic manifestations seem to be a hidden, frequent, post-epidemic condition. These findings should be considered in the development of preventive measures.

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.

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.

Ross River virus disease in Australia, 1886-1998, with analysis of risk factors associated with outbreaks

Ross River virus (RR) is a mosquito-borne arbovirus responsible for outbreaks of polyarthritic disease throughout Australia. To better understand human and environmental factors driving such events, 57 historical reports on RR outbreaks between 1896 and 1998 were examined collectively. The magnitude, regularity, seasonality, and locality of outbreaks were found to be wide ranging; however, analysis of climatic and tidal data highlighted that environmental conditions act differently in tropical, arid, and temperate regions. Overall, rainfall seems to be the single most important risk factor, with over 90% of major outbreak locations receiving higher than average rainfall in preceding months. Many temperatures were close to average, particularly in tropical populations; however, in arid regions, below average maximum temperatures predominated, and in southeast temperate regions, above average minimum temperatures predominated. High spring tides preceded coastal outbreaks, both in the presence and absence of rainfall, and the relationship between rainfall and the Southern Oscillation Index and La Niña episodes suggest they may be useful predictive tools, but only in southeast temperate regions. Such heterogeneity predisposing outbreaks supports the notion that there are different RR epidemiologies throughout Australia but also suggests that generic parameters for the prediction and control of outbreaks are of limited use at a local level.

Ross River virus disease in tropical Queensland: evolution of rheumatic manifestations in an inception cohort followed for six months

OBJECTIVE

To describe the natural history of rheumatic manifestations of Ross River virus (RRV) disease.

DESIGN

Prospective longitudinal clinical review.

SETTING

North Queensland local government areas of Cairns, Douglas, Mareeba and Atherton during January to May 1998.

PARTICIPANTS

General practice patients diagnosed with RRV disease on the basis of symptoms and a positive RRV IgM result.

MAIN OUTCOME MEASURES

Rheumatic symptoms and signs assessed as soon as possible after disease onset and on two subsequent occasions (up to 6.5 months after onset).

RESULTS

57 patients were recruited, 47 of whom were reviewed three times (at means of 1.1, 2.4 and 3.6 months after disease onset). Results are reported for these 47: 46 (98%) complained of joint pain at first review, with the ankles, wrists, fingers, knees and metacarpophalangeal joints (II-IV) most commonly involved. Prevalence of joint pain decreased progressively on second and third reviews, both overall (92% and 68% of patients, respectively), and in the five joints most commonly affected. The prevalence of other common rheumatic symptoms and signs, and use of non-steroidal anti-inflammatory drugs, also progressively declined over the three reviews.

CONCLUSIONS

Earlier studies may have overestimated the prevalence and duration of symptoms in RRV disease. Progressive resolution over 3-6 months appears usual.

Natural history of Ross River virus-induced epidemic polyarthritis

OBJECTIVE

To describe the natural history, treatment and cost of Ross River virus-induced epidemic polyarthritis (RRV disease).

DESIGN

Questionnaire-based longitudinal prospective study.

PARTICIPANTS AND SETTING

Patients in the greater Brisbane area, Queensland, diagnosed with RRV disease by their general practitioners based on clinical symptoms and paired serological tests between November 1997 and April 1999.

MAIN OUTCOME MEASURES

Scores on two validated quality-of-life questionnaires (Clinical Health Assessment Questionnaire and Medical Outcomes Study Short Form 36) were obtained soon after diagnosis and one, two, three, six and 12 months thereafter. Scores were compared between patients diagnosed with RRV disease alone and those with RRV disease plus other conditions.

RESULTS

67 patients were enrolled. Most patients with RRV disease alone had severe acute symptoms, but followed a consistent path to recovery within three to six months. Other conditions, often chronic rheumatic diseases or depression, were identified in half the cohort; their quality-of-life scores suggested stable chronic illness between six and 12 months after diagnosis. Non-steroidal anti-inflammatory drugs (NSAIDs) were taken by 58% of patients (average use, 7.6 weeks; range, 2-22 weeks). Time off work averaged 1.9 days, and direct cost to the community was estimated as 1018 Australian dollars per patient.

CONCLUSIONS

Symptom duration and frequency of long-term symptoms may have been overestimated by previous studies of RRV disease. Disease persisting six to 12 months after RRV diagnosis was largely attributable to other conditions, highlighting the need to seek other diagnoses in RRV patients with persistent symptoms.

Predicting Ross River virus epidemics from regional weather data

BACKGROUND

Diseases caused by arboviruses cause extensive mortality and morbidity throughout the world. Weather directly affects the breeding, abundance, and survival of mosquitoes, the principal vector of many arboviruses. The goal of this study was to test whether climate variables could predict with high levels of accuracy (more than 70%) epidemics of one arbovirus, Ross River virus disease.

METHODS

Weather data from two regions in southeastern Australia were matched with Ross River virus disease data for the period 1991 to 1999. Our aim was to develop simple models for the probability of the occurrence of an epidemic in an area in a given year.

RESULTS

Two predictable epidemic patterns emerged, after either high summer rainfalls or high winter rainfalls. A prerequisite relating to host-virus dynamics was lower than average spring rainfall in the preepidemic year. The sensitivity of the model was 96% for Region 1 and 73% for Region 2.

CONCLUSIONS

Early warning of weather conditions conducive to outbreaks of Ross River virus disease is possible at the regional level with a high degree of accuracy. Our models may have application as a decision tool for health authorities to use in risk-management planning.

Ross River virus: ecology and distribution

Ross River virus is the most common mosquito-borne pathogen in Australia, and approximately 5000 human cases are reported annually. The infection is not fatal, but there is considerable morbidity associated with a debilitating polyarthritis that is the major symptom. The virus is annually active in most regions of Australia, but exists as strains that vary in virulence. Native macropods are thought to be the natural vertebrate hosts, although horses and humans may be involved during epidemic activity, and vertical transmission of the virus occurs in mosquitoes. Different mosquito species are involved as vectors in various regions and in different seasonal and environmental conditions. In coastal areas the saltmarsh mosquitoes Aedes camptorhynchus and Ae. vigilax are the most important vectors in southern and northern regions, respectively, whereas in inland areas Culex annulirostris is the most important vector, although various Aedes species can be involved depending on region and conditions, and the epidemiology of the disease and vector control imperatives vary with circumstance concomitantly.

Ross River virus transmission, infection, and disease: a cross-disciplinary review

Ross River virus (RRV) is a fascinating, important arbovirus that is endemic and enzootic in Australia and Papua New Guinea and was epidemic in the South Pacific in 1979 and 1980. Infection with RRV may cause disease in humans, typically presenting as peripheral polyarthralgia or arthritis, sometimes with fever and rash. RRV disease notifications in Australia average 5,000 per year. The first well-described outbreak occurred in 1928. During World War II there were more outbreaks, and the name epidemic polyarthritis was applied. During a 1956 outbreak, epidemic polyarthritis was linked serologically to a group A arbovirus (Alphavirus). The virus was subsequently isolated from Aedes vigilax mosquitoes in 1963 and then from epidemic polyarthritis patients. We review the literature on the evolutionary biology of RRV, immune response to infection, pathogenesis, serologic diagnosis, disease manifestations, the extraordinary variety of vertebrate hosts, mosquito vectors, and transmission cycles, antibody prevalence, epidemiology of asymptomatic and symptomatic human infection, infection risks, and public health impact. RRV arthritis is due to joint infection, and treatment is currently based on empirical anti-inflammatory regimens. Further research on pathogenesis may improve understanding of the natural history of this disease and lead to new treatment strategies. The burden of morbidity is considerable, and the virus could spread to other countries. To justify and design preventive programs, we need accurate data on economic costs and better understanding of transmission and behavioral and environmental risks.

Arboviruses associated with human disease in Australia

Mosquito-borne arboviruses are an important public health issue in Australia. The alphaviruses Ross River and Barmah Forest virus are widespread and active annually, and cause debilitating polyarthritis. The flaviviruses Murray Valley encephalitis, Kunjin and Japanese encephalitis virus are restricted in distribution and activity but may cause life-threatening illness, and dengue viruses are active in some areas.

Queenslanders' use of personal strategies to minimise risk of mosquito-borne disease

OBJECTIVE

To describe Queenslanders' awareness, knowledge and attitudes towards mosquito-borne diseases and their transmission, and to determine which factors influence the adoption of effective individual prevention strategies.

METHODS

In 1995-6, cross-sectional surveys of adult residents in the western suburbs of Brisbane and registered voters in Cairns were conducted. Forced entry logistic regression was used to predict use of personal protection and elimination of domestic breeding sites in the two cities.

RESULTS

Final sample sizes were 347 in Cairns and 165 in Brisbane with response rates of approximately 70%. RRVD awareness was nearly universal in both cities. A majority of residents (60% in Brisbane and 65% in Cairns) report they are careful to avoid being bitten by mosquitoes. 25% of Cairns residents and 18% of Brisbane residents report always using some method of personal protection. Cairns residents are also more likely to say that they actively prevent mosquitoes from breeding in their yards (76% in Brisbane and 87% in Cairns). Knowledge of mosquitoes and disease transmission was slightly higher in Cairns. In Brisbane, dislike of mosquitoes and being regularly bitten were significant in the multivariate model predicting personal protection, whereas concern for disease and being female were significant in Cairns. Concern about disease was a significant predictor of eliminating breeding sites in both cities.

CONCLUSIONS

Raising concern about mosquito-borne disease can increase use of personal prevention strategies. However, providing information on prevention strategies may not be effective. The most effective strategies are not practiced or seen by the public to be related to minimising risk of disease.

IMPLICATIONS

Greater emphasis in health promotion campaigns should be placed on encouraging permanent alterations to the domestic environment rather than temporary methods that are difficult to sustain and not effective against the common vectors for mosquito-borne diseases in Queensland. Educational messages should explicitly link preventive behaviours with the reduction in the likelihood of contracting a serious disease.

Self-reported morbidity of Barmah Forest virus infection on the north coast of New South Wales

OBJECTIVE

To describe the clinical features and disability associated with Barmah Forest virus (BFV) infection.

DESIGN

Retrospective postal survey.

SETTING

North Coast Public Health Unit, Lismore, New South Wales, January to October 1995.

SUBJECTS

All 84 subjects notified by mandatory laboratory reporting as positive for BFV IgM by enzyme-linked immunosorbent assay.

OUTCOME MEASURES

Demographic information, self-reported symptoms, disability and treatment.

RESULTS

Response rate was 77%. Peak incidence was in the 30-50 years age group, with almost identical numbers of men and women affected. The most common symptoms were lethargy (89%), joint pain (82%) and rash (68%). These were also generally the first symptoms to appear. Thirty of 54 respondents (56%) reported time off work and 27 of 53 (51%) reported illness lasting more than six months. Those who had a rash were significantly more likely to have recovered by the time of the survey than those who had no rash (odds ratio, 10.3; 95% confidence interval, 1.8-76.6). No treatment led to more than slight relief of symptoms.

CONCLUSION

Symptoms of BFV infection appear similar to those of the better-known Ross River virus infection, and clinicians should consider both in patients with symptoms of arboviral disease. The wide distribution and long duration of illness make BFV a potentially significant cause of morbidity in Australia. A possible association between the presence of a rash and improved prognosis needs further investigation.