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.