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A long-haul travel syndrome?
Shigella infection is the least common of the gastroenteritis-inducing organisms which are associated with reactive arthritis (ReA) in developed countries, reflecting the scarcity of the organism in these environments. A recent thorough survey of Shigella infected subjects in Finland1 describes an annual incidence of Shigella induced ReA of only 1.3 per million. This compares with the incidence figures of 46 per million for ReA due to Chlamydia infection, and 50 per million for other enteric pathogens, noted in a survey of the Oslo population.2 However, the relevant denominator for Shigella induced ReA is not the population of Finland, but the population visiting distant travel destinations—for example Egypt, India, Thailand, Congo, and Turkey—all countries where the infection was acquired by the Finnish patients. Although these countries, particularly, Turkey, are increasingly common holiday destinations for sun-starved Northern Europeans, well under 5% of the population visit such countries in any 1 year, so the incidence of ReA is more like 30–40 per million in the exposed population.
SHIGELLA SPECIES
Of the Shigella species encountered in sunny places, the commonest is S sonnei. This might be considered a source of comfort to the intending B27+ traveller, because S sonnei was at one time considered not to induce ReA. The recent paper from Finland1 dispels this idea; S sonnei was the commonest of the Shigellae isolated from patients who developed ReA, and there appeared to be no significant difference in the incidence of ReA following S sonnei and S flexneri infection. Why this difference from previous reports? Although cases of ReA following S sonnei infection were reported as long ago as 1947, and there were additional reports in 1988 (three cases3) and 2002 (a sexually acquired case4), two other major reports have been interpreted as exonerating …