Reviews of pediatric research

Mixed RSV-pertussis infections common in infants

Investigators set out to determine how often respiratory viral infections in infants occur with Bordetella pertussis, particularly with respiratory syncytial virus (RSV), and the clinical presentation of such mixed infections. They analyzed data for 117 infants younger than 6 months who were hospitalized for a respiratory tract infection during the five-month period of an RSV epidemic. The infants were monitored for respiratory viral antigens, using a direct immunofluorescence test. In addition, any infant with a prominent cough was tested for B pertussis with a polymerase chain reaction assay. The study was conducted in Finland, where compliance with recommended infant pertussis vaccinations at 3, 5, and 12 months is 95.6%.

RSV infection was documented in 91 (78%) of the study infants. In two infants, parainfluenza viruses were detected; no other viruses were found. Pertussis was present in nine (8%) of the infants, all but two of whom had mixed RSV-pertussis infection (one was coinfected with parainfluenza virus and one had pertussis alone). A relatively large proportion-7% of infants who were not vaccinated or incompletely vaccinated-were infected with B pertussis.

Commentary:

Even though pertussis immunization starts at 3 months in Finland, the information presented here is helpful. The authors considered pertussis only in children with cough, and when they looked for it, they found it-frequently. Severity of symptoms and lab tests did not help differentiate between those with and without pertussis. I presume that means that lymphocytosis was not a consistent finding, though this is not specifically mentioned. There is also no mention of a whoop before the cough, which is not surprising in young infants. The lesson here is to keep pertussis in mind, even when you are up to your neck in RSV.

Older preschoolers' anemia is generally new, not persistent

To assess anemia incidence and persistence in low-income preschool children in the US, investigators examined data from the Centers for Disease Control and Prevention's Pediatric Nutrition Surveillance System for four large groups of geographically and racially diverse children (more than 300,000 in each group). These children had a baseline hemoglobin measurement at 12, 18, 24, or 36 months of age, and a follow-up hemoglobin measurement was taken about a year later. Anemia was defined as a hemoglobin level of lower than 11.0 g/dL in children up to 24 months, or lower than 11.1 g/dL in children 24 months or older.

Prevalence of anemia at baseline decreased with age, from 13% at 18 months, to 12.7% at 24 months, and 9.9% at 36 months. Anemia incidence (new cases) also decreased with age, from 12.9% at 24 months, to 9.7% at 36 months, to 6.9% at 48 months. Anemia persistence (anemia at baseline and at follow-up) was about 30% at each follow-up age. Of total anemia cases at follow-up in each group, about 70% of cases were new.

Anemia incidence was highest in black children at every age, though the discrepancy with white children declined with age. Asian/Pacific Islander children also had elevated anemia incidence, especially at 30 months. Beginning at 30 months, Native American children had the lowest incidence of anemia. All these racial differences remained after controlling for sex, birth weight, height-for-age percentile, weight-for-height percentile, and breastfeeding history (Cusick SE, et al: J Pediatr 2007;150:422).