In-Depth Analysis of Patients with Confirmed Novel H1N1 Influenza Admitted to Pediatric Intensive Care Unit

Background: While abundant literature exists regarding the epidemiology of novel H1N1 influenza in general populations, data describing this occurrence in the pediatric population is very limited.

Objective: To describe and analyze the patterns of confirmed Novel H1N1 Influenza patients admitted to the Pediatric Intensive Care Unit (PICU) of the largest pediatric hospital in the United States.

Methods: Between September 1 and October 31, 2009, medical records of all patients admitted to PICU (N=33) with confirmed novel H1N1 influenza were reviewed. A standardized form, provided and approved by the Texas Health Department, was used to collect the data. The information included, but was not limited to, demographic data, risk factors, bacterial co-infections, laboratory method and results. The data was analyzed by the infection preventionist.

Results: Of the 33 study patients, the ages ranged from 3 months to 20 years old with a mean of 6.5 years old. A higher percentage of males (73%) compared to females (27%) was observed in this study group. Of all these Texas-residing patients, almost half of them resided in Harris County, which is the largest county in Texas, by population. Hispanics made up the majority of the cases (46%) followed by Whites (27%), African Americans (12%), and Others (15%). Less than half of the study cases (48%) were admitted with fever >101°F.  Eighteen out of the 33 cases (54%) were described to have underlying health conditions with cardiac disease as the leading underlying health condition (39%) followed by asthma (17%), kidney disease (11%), and others (33%).The average length of stay in PICU was approximately 12 days. Secondary bacterial co- infection was identified in 45% of the study patients. MRSA ( Methicillin-resistant Staphylococcus aureus) in respiratory specimens was isolated in 40% of the patients with the bacterial co-infection. All the specimens in this study were tested using three different methodologies: RT-PCR, a commercial rapid EIA, and a routine viral culture. In this study, the sensitivity was 100%, 33%, and 45%, with the RT-PCR, commercial rapid EIA, and routine viral culture, respectively. The mortality rate of the study population was 6% (2 cases), with one case having an underlying health condition while the other had none.

Conclusions: In this study, the disease occurred more frequently in males than females. Nearly half of the cases (46%) had no underlying health conditions. The RT-PCR method appears to have been much more sensitive compared to commercial rapid EIA and the routine viral culture. The high incidence of bacterial co-infection with MRSA in this study requires further investigation. The result of this descriptive study provides a better understanding of this disease pattern in PICU patients, however, larger sample sizes and more rigorous study design may be necessary to further document specifics regarding this disease in pediatric populations.