Pertussis--an under-diagnosed disease with high morbidity in Singapore children

Since the introduction of the pertussis vaccine into the standard immunization program, very few cases of pertussis have been detected. In 2007, it was felt that the number of cases being admitted for pertussis had increased and this was verified on a retrospective review done from 2004 to 2007 of children diagnosed with pertussis in KK Women's and Children's Hospital.

To review the cases diagnosed with pertussis, the demographic profile and the outcome of these patients.

A retrospective review was done of patients diagnosed with pertussis from 2004 to 2007. The patients were identified from records of the positive results obtained from the microbiology laboratory.

In the preceding years, only 1-2 cases/year were reported with pertussis but this increased to 33 cases in 2007. 45 confirmed cases were analysed. Most infections were in infants below 6 months old (mean age 4.1 months) and almost all were not vaccinated. The average length of stay was 4.96 days (Range 2-14 days, SD 2.55). Children under 6 months had more severe disease in terms of ICU admissions (6% vs. 0%, p=0.70) and average length of stay (5.1 vs. 3.5 days, p=0.25) as compared to those above 6 months of age. Exposure to a symptomatic adult was documented in 64%, mainly parents (45%), older siblings (29%). Healthcare workers may also be a source of infection as one child had symptoms as early as the first week of life and none of the family members were coughing.

There is a resurgence of pertussis in recent years with high morbidity in children who have not been vaccinated. A booster with Tdap vaccine should be considered for young adults and healthcare workers looking after children.