Shigella dysenteriae serotype 1 in west Africa: intervention strategy for an outbreak in Sierra Leone

In November 1999, a Médecins Sans Frontières team based in the southeastern part of Sierra Leone reported an increased number of cases of bloody diarrhoea. Shigella dysenteriae serotype 1 (Sd1) was isolated in the early cases. A total of 4218 cases of dysentery were reported in Kenema district from December, 1999, to March, 2000. The overall attack rate was 7•5%. The attack rate was higher among children younger than 5 years than in the rest of the population (11•2% vs 6•8%; relative risk=1•6; 95% CI 1•5–1•8). The case fatality was 3•1%, also higher for children younger than 5 years (6•1% vs 2•1%; relative risk=2•9; 95% CI 2•1–4•1]). Among 583 patients regarded at increased risk of death who were treated with ciprofloxacin in isolation centres, case fatality was 0•9%. A 5-day ciprofloxacin regimen, targeted to the most severe cases of bloody diarrhoea, was highly effective. This is the first time a large outbreak caused by Sd1 has been reported in west Africa.