Increased H1N1 infection rate in children with asthma.

RATIONALE: The 2009 H1N1 flu appeared to cause more severe cold symptoms during the 2009-2010 flu season. OBJECTIVES: We evaluated H1N1 infections during peak viral season in children with and without asthma to determine whether the H1N1 infectivity rate and illness severity were greater in subjects with asthma. METHODS: One hundred and eighty children, 4-12 years of age, provided eight consecutive weekly nasal mucus samples from September 5 through October 24, 2009, and scored cold and asthma symptoms daily. Viral diagnostics were performed for all nasal samples. MEASUREMENTS AND MAIN RESULTS: One hundred and sixty-one children (95 with asthma, 66 without asthma) completed at least 6 of the 8 nasal samples. The incidence of H1N1 infection was significantly higher in children with asthma (41%) than in children without asthma (24%; odds ratio, 4; 95% confidence interval, 1.8-9; P < 0.001), but rates of human rhinovirus infection (90% each) and other viral infections (47 vs. 41%) were similar. In children with asthma, there was a nonsignificant trend for increased loss of asthma control during H1N1 infections compared with human rhinovirus infections (38 vs. 21%; odds ratio, 2.6; 95% confidence interval, 0.9-7.2; P = 0.07). CONCLUSIONS: During peak 2009 H1N1 flu season, children with asthma were infected almost twice as often with H1N1 compared with other respiratory viruses. H1N1 infection also caused increased severity of cold symptoms compared with other viral infections. Given the increased susceptibility of children with asthma to infection, these findings reinforce the need for yearly influenza vaccination to prevent infection, and raise new questions about the mechanism for enhanced susceptibility to influenza infection in asthma.

Weekly monitoring of children with asthma for infections and illness during common cold seasons.

BACKGROUND: Exacerbations of childhood asthma and rhinovirus infections both peak during the spring and fall, suggesting that viral infections are major contributors to seasonal asthma morbidity. OBJECTIVES: We sought to evaluate rhinovirus infections during peak seasons in children with asthma and to analyze relationships between viral infection and illness severity. METHODS: Fifty-eight children aged 6 to 8 years with asthma provided 5 consecutive weekly nasal lavage samples during September and April; symptoms, medication use, and peak flow were recorded. Rhinoviruses were identified by using multiplex PCR and partial sequencing of viral genomes. RESULTS: Viruses were detected in 36% to 50% of the specimens, and 72% to 99% of the viruses were rhinoviruses. There were 52 different strains (including 16 human rhinovirus C) among the 169 rhinovirus isolates; no strains were found in more than 2 collection periods, and all but 2 children had a respiratory tract infection. Virus-positive weeks were associated with greater cold and asthma symptom severity (P < .0001 and P = .0002, respectively). Furthermore, virus-positive illnesses had increased duration and severity of cold and asthma symptoms and more frequent loss of asthma control (47% vs 22%, P = .008). Although allergen-sensitized versus nonsensitized children had the same number of viral infections, the former had 47% more symptomatic viral illnesses (1.19 vs 0.81 per month, P = .03). CONCLUSIONS: Rhinovirus infections are nearly universal in children with asthma during common cold seasons, likely because of a plethora of new strains appearing each season. Illnesses associated with viruses have greater duration and severity. Finally, atopic asthmatic children experienced more frequent and severe virus-induced illnesses.