Outbreak of boils in an Alaskan village: a case-control study

Abstract

Objective: To determine whether taking steam baths was associated with furunculosis and to evaluate possible risk factors for the occurrence of boils during a large outbreak in Alaska.

Design: A cohort study of village residents, a case-control study, and assessment of environmental cultures taken from steam baths.

Setting: Village in southwestern Alaska.

Participants: 1 adult member from 77 of the 92 households in the village was interviewed; 115 residents with at least one boil occurring between January 1 and December 12, 1996 were considered to be cases; 209 residents without a boil acted as the control group. All 459 village residents were included in the cohort study.

Main outcome measure: Rate of infection among all residents and residents who regularly took steam baths, risk factors for infection, and relative risk of infection.

Results: 115 people (25%) had had at least one boil. Men were more likely to have had a boil than women (relative risk 1.5; 95% confidence interval 1.1 to 2.2). The highest rate of infection was among people ages 25-34 years (32/76; 42%). No children younger than 2 years had had boils. Boils were associated with using a steam bath (odds ratio 8.1; 3.3 to 20.1). Among those who used a steam bath, the likelihood of developing boils was reduced by routinely sitting on a towel while bathing, which women were more likely to do, and bathing with fewer than 8 people. Of the 93 samples taken from steam baths, one Staphylococcus aureus isolate was obtained from a bench in an outer dressing room.

Conclusion: Using a steam bath was associated with developing boils in this outbreak in a village in Alaska. People should be advised to sit on towels while using steam baths.

Figure 1

Number of people diagnosed with first and subsequent infections with boils during two-week intervals, January 1 through December 12, 1996