Invasive Haemophilus influenzae type b disease in children less than 5 years of age in Minnesota and in Dallas County, Texas, 1983-1984.

During 1983 and 1984, 733 cases of invasive Haemophilus influenzae type b disease in children less than 5 years of age were identified in Minnesota and in Dallas County, Texas. The overall incidence of disease was lower in Minnesota than in Dallas County. However, among urban residents, the rates of disease for whites were similar in the two areas. A higher rate of disease among whites in urban Minnesota compared with rural Minnesota resulted from an increased rate of cases for diagnoses other than meningitis. Local practices might have affected the rate of certain diagnoses, since ascertainment of Hib disease other than meningitis is more dependent on diagnostic practices than is diagnosis of meningitis. These data suggest that the incidence of invasive H. influenzae type b disease is influenced by the racial composition of the population, the rates of disease in specific subgroups, and possibly by local medical practices. Understanding the factors that contribute to the incidence of disease is necessary to interpret variations in different populations and changes over time.

Excretion of Haemophilus influenzae type b polysaccharide antigen in urine of healthy nasopharyngeal carriers.

We measured concentrations of Haemophilus influenzae type b (Hib) polysaccharide antigen by ELISA in urine samples from 81 healthy North American children with positive or negative throat cultures for Hib, to investigate the possibility that asymptomatic carriers may have antigenuria. For comparison, we determined the concentrations of Hib polysaccharide antigen in urine samples from 56 patients with proven Haemophilus disease, including 13 children with lower respiratory infections who resided in developing countries. Among the healthy children, antigen was detected in the urine of seven of 19 (37%) carriers of Hib compared with one of 62 (2%) children with negative throat cultures (p less than 0.001). Among the patients with invasive Haemophilus infections, 93% had antigen detected. Although there was overlap in the concentrations of antigen in the positive urines from the asymptomatic carriers and those of the ill patients, the concentrations of the ill patients were higher than those of the carriers. The respective geometric means of the positive patients were: American patients with meningitis, 42.5 ng/mL (range 1.7-9800 ng/mL); American patients with infections not involving the CNS, 5.8 ng/mL (range: 1.0-96 ng/mL); patients from developing countries with lower respiratory infections, 29.6 ng/mL (range: 0.9-5290), and American asymptomatic carriers, 1.9 ng/mL (range: 0.6-16.7 ng/mL). Thus, antigenuria is present in a high proportion of healthy children with positive throat cultures for Hib, and the antigen concentrations of the carriers overlap those of ill patients. These results suggest that either mucosal colonization itself is sufficient to produce antigen-uria, or asymptomatic carriers may be experiencing asymptomatic invasive Hib infection.

Haemophilus influenzae type b in respiratory secretions.

Oral and respiratory secretions of 31 children who were healthy or had mild upper respiratory infection, and who had a positive throat culture for Haemophilus influenzae type b, were cultured to determine which secretions contain this organism and how long it can be recovered from fomites. Rhinorrhea was present in 11 of 31 (34%) children and nasal mucus was positive for H. influenzae type b in 10 (91%). In 5 of these children the concentration of H. influenzae type b in nasal mucus was 10(4) to 10(7) colony-forming units/ml3. H. influenzae type b in nasal mucus applied to fomites were recovered for 12 hours. Cultures of saliva and cough secretions compared with nasal mucus were less often positive (3 of 31, P less than 0.001; 3 of 25, P less than 0.001, respectively) and contained fewer H. influenzae type b (5 and 15 colony-forming units, respectively). H. influenzae type b was recovered from the hand of 2 of 27 (7%) children; both children had positive cultures of saliva. These data indicate that H. influenzae type b can be found in oral and respiratory secretions of pharyngeal carriers and can contaminate children's hands. Nasal mucus was the most consistently positive secretion and contained the largest number of bacteria. Careful management of nasal mucus secretions is warranted in settings where transmission could occur to susceptible children.

Risk of subsequent disease among day-care contacts of patients with systemic Hemophilus influenzae type B disease.

There is controversy about whether to provide rifampin prophylaxis routinely to contacts in day-care facilities of a patient with a primary case of Hemophilus influenzae type b disease. We prospectively investigated primary cases of H. influenzae type b disease in day-care facilities in Dallas County, Texas, to determine the rate of subsequent disease among contacts. Ninety-one children with primary cases of H. influenzae type b disease who were attending day-care facilities were enrolled from October 1982 to October 1984. A total of 587 classroom contacts of these children under four years of age were not given rifampin. During 60 days of follow-up, there was one subsequent case in a classroom contact. Untreated children under two years of age who were directly exposed to a patient with a primary case were considered to be at highest risk of disease, but there were no subsequent cases in this group of 361 children. However, there were two cases in new enrollees who started attending day-care facilities during the 60-day follow-up period but who were not exposed to a patient with a primary case. At day-care centers in which there was a second case during the follow-up period, there was a high prevalence of colonization with H. influenzae type b in both patient and nonpatient groups of preschool children. These data indicate that the rate of subsequent disease in classroom contacts of patients in day-care facilities is lower than that reported in households (1 of 587 vs. 20 of 829, P = 0.001) and that this rate may be similar to the base rate of primary disease in day-care facilities. We conclude that rifampin prophylaxis may not be appropriate after the occurrence of a primary case of H. influenzae type b disease in a day-care facility in Dallas County.