RISK OF SECONDARY HAEMOPHILUS INFLUENZAE TYPE B (Hib) DISEASE IN DAY CARE

Abstract

In 1982, the MDH initiated a statewide, prospective, active surveillance system for Hib disease. During the first year, we identified 219 cases among children ≤12 years of age. The median time of case report to MDH following onset of illness was 8.2 days. 80 cases (39%) occurred among children attending day care. Of 971 nonsibling-child day care contacts from the same room, 962 (99%) were followed for 60 days. 200 of the 962 (21%) received rifampin prophylaxis. No Hib cases occurred among this group or the 762 contact children who did not receive rifampin, including 137 <24 mos of age; and 269, 24 to 47 mos of age. The secondary attack rate for day care contacts <48 mos is lower (p=0.003) than that reported for household contacts of similar age in a national study. In the present study the distribution of outer membrane protein subtypes (OMP) was similar to that previously reported from 22 states. However, subtype 1H strains previously associated with an increased secondary attack rate in day care, were isolated more frequently from primary cases in day care than in non-day care (53% v. 32%, p=0.03). With the exception of day care, there was no relation between OMP subtypes and age, gender, onset of disease, or geographic residence of the case. Our data suggest that the risk of secondary Hib disease in day care is lower than that previously reported for family-sibling contacts. Further, the frequency of 1H strains among primary cases is higher than in non-day care population.

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