Rheumatology 2001; 40: 1319-1320
© 2001 British Society for Rheumatology
Letters to the Editor |
Prolonged arthritis associated with Sindbis-related (Pogosta) virus infection
Tropical Public Health Unit and
1 Cairns Base Hospital, Cairns and
2 Australian Centre for International and Tropical Health and Nutrition, University of Queensland, Brisbane, Queensland, Australia
SIR, We have read the article by Laine et al. [1] with interest. They found that 2.5 yr after Pogosta virus infection 50% of 26 patients still had symptoms. We are concerned that perhaps the authors have overinterpreted their findings, mistaking association for causation.
Their paper draws comparisons with Ross River (RR) virus, an Alphavirus that causes similar symptoms to Sindbis virus. Several studies in the 1990s [2 and others] searched for symptoms by postal questionnaire amongst patients with serological evidence of RR virus infection and suggested that infection with RR virus resulted in frequent chronic symptoms. All these studies were flawed because they did not use standardized health status questionnaires, there were no control groups, patients were questioned about symptoms long after onset, patients were not examined, alternative diagnoses were not sought, and participation bias and loss to follow-up were substantial. Recent studies of RR virus in Cairns and elsewhere in Australia [3] have shown a consistent pattern of recovery over a few months using prospective review and standardized health questionnaires. Parallels can be drawn with Lyme disease, which can also cause rheumatic symptoms. Burdge and O'Hanlon [4] found that alternative diagnoses could be suggested in 77% of a group of patients apparently suffering chronic symptoms from infection with Borrelia burgdorferi.
The prevalence of rheumatic symptoms in the community is high [5]; they are therefore likely to occur frequently in subjects infected by RR or Sindbis virus, or B. burgdorferi, without a causal relationship existing.
The causal inferences of Laine et al. can be assessed against the criteria for causation suggested by Bradford Hill [6]. They succeed with temporality and consistency, because putative cause precedes effect and because similar results have been found before. They fail, however, with strength as only 50% showed symptoms, specificity because of the widespread nature of rheumatic symptoms indicated above, and biological gradient and experiment are not considered. Analogy with RR virus is discussed, but flaws in recent studies of RR virus weaken the application of this criterion. Coherence is achieved in that the findings do not seriously conflict with what is known of Pogosta disease. Lastly plausibility is only achieved by reference to flawed reports on RR virus.
As clinicians we must consider the relevance of this paper to our practice. This is not a purely academic argument. Our experience with RR virus suggests that results of studies such as the one by Laine et al. [1] should be interpreted with caution. Great harm can come from the dissemination of flawed evidence and incorrect diagnosis can result in inappropriate treatment and advice, inaccurate self-diagnosis and even unfair litigation in the quest for blame and compensation. On the public health front, it is essential that information provided to the public be based on solid scientific foundations.
Notes
Correspondence to: D. Harley, Public Health Registrar, Tropical Public Health Unit, PO Box 1103, Cairns, Queensland 4870, Australia. 
References
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Laine M, Luukkainen R, Jalava J, Ilonen J, Kuusisto P, Toivanen A. Prolonged arthritis associated with Sindbis-related (Pogosta) virus infection. Rheumatology2000;39:1272–4.
[Abstract/Free Full Text] - Selden SM, Cameron AS. Changing epidemiology of Ross River virus disease in South Australia. Med J Aust1996;165:313–7.[ISI][Medline]
- Harley D, Sleigh A, Bossingham D, Ritchie S, Williams G. Ross River virus disease from a North Queensland public health perspective. Arbovirus Res Aust2000;8:171–6.
- Burdge DR, O'Hanlon DP. Experience at a referral center for patients with suspected Lyme disease in an area of nonendemicity: First 65 patients. Clin Infect Dis1993;16:558–60.[ISI][Medline]
- Verbrugge LM, Ascione FJ. Exploring the iceberg: Common symptoms and how people care for them. Med Care1987;25:539–69.[ISI][Medline]
- Bradford Hill A. The environment and disease: Association or causation? Proc R Soc Med1965;58:295–300.[ISI][Medline]
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