Hemophilus influenzae type b disease in a day-care center. Report of an outbreak.

Four episodes of serious Hemophilus influenzae type b infection occurred in three children attending a day-care center. This was 100 times the expected annual total. The pharyngeal carriage rate of Hib was 60% for siblings of patients, 20% for adult household contacts, and 5% for well children at the center. No carriers were found in control populations. Escherichia coli K100, which cross-reacts serologically with Hib, was found in rectal swabs of 20% of family contacts of patients and 3.5% of well children at the center. It was recovered from two of seven persons who carried Hib in the pharynx and two of 75 who did not (P = 0.035), suggesting that carriage of one organism may facilitate carriage of the other. In a randomized prospective trial with 85 patient contact, Hib carriage was eradicated in all of four carriers given ampicillin and in all of three given rifampin. There were no statistically significant differences in the rate of adverse reactions in the two treatment groups. No further cases were reported.