Children hospitalized with 2009 novel influenza A(H1N1) in California

Abstract

Objective: To describe clinical and epidemiologic features of 2009 novel influenza A(H1N1) in children.

Design: Analysis of data obtained from standardized report forms and medical records.

Setting: Statewide public health surveillance in California.

Participants: Three hundred forty-five children who were hospitalized with or died of 2009 novel influenza A(H1N1).

Main exposure: Laboratory-confirmed 2009 novel influenza A(H1N1).

Main outcome measures: Hospitalization and death.

Results: From April 23 to August 11, 2009, 345 cases in children younger than 18 years were reported. The median age was 6 years. The hospitalization rate per 100 000 per 110 days was 3.5 (0.97 per 100 000 person-months), with rates highest in infants younger than 6 months (13.9 per 100 000 or 3.86 per 100 000 person-months). Two-thirds (230; 67%) had comorbidities. More than half (163 of 278; 59%) had pneumonia, 94 (27%) required intensive care, and 9 (3%) died; in 3 fatal cases (33%), children had secondary bacterial infections. More than two-thirds (221 of 319; 69%) received antiviral treatment, 44% (88 of 202) within 48 hours of symptom onset. In multivariate analysis, congenital heart disease (odds ratio [OR], 5.0; 95% confidence interval [CI], 1.9-13.5) and cerebral palsy/developmental delay (OR, 3.5; 95% CI, 1.7-7.4) were associated with increased likelihood of intensive care unit admission and/or death; likelihood was decreased in Hispanic (OR, 0.4; 95% CI, 0.2-0.8) and black (OR, 0.3; 95% CI, 0.1-1.0) children compared with white children.

Conclusions: More than one-quarter of children hospitalized with 2009 novel influenza A(H1N1) reported to the California Department of Public Health required intensive care and/or died. Regardless of rapid test results, when 2009 novel influenza A(H1N1) is circulating, clinicians should maintain a high suspicion in children with febrile respiratory illness and promptly treat those with underlying risk factors, especially infants.