The author declares that they have no competing interests Authors' contributions NTLH -conception and design, acquisition of data, analysis and interpretation of data, has been involved in drafting the manuscript and have given final approval of the version to be published. ML -Analysis and interpretation of data, has been involved in drafting the manuscript and have given final approval of the version to be published. HFLW -conception and design, acquisition of data, interpretation of data, revising it critically for important intellectual content and have given final approval of the version to be published. DTT -Laboratory analysis and have given final approval of the version to be published. WT -conception and design, acquisition of data, revising it critically for important intellectual content and have given final approval of the version to be published. PH -conception and design, acquisition of data, interpretation of data, revising it critically for important intellectual content and have given final approval of the version to be published. NVT-Laboratory analysis and have given final approval of the version to be published. NTMH -Acquisition of data and have given final approval of the version to be published. TL -Revising it critically for important intellectual content and have given final approval of the version to be published. NVK -conception and design, acquisition of data and have given final approval of the version to be published. All authors read and approved the final manuscript. Prospective application of clinician-performed lung ultrasonography during the 2009 H1N1 influenza A pandemic: distinguishing viral from bacterial pneumonia BACKGROUND: Emergency department visits quadrupled with the initial onset and surge during the 2009 H1N1 influenza pandemic in New York City from April to June 2009. This time period was unique in that >90% of the circulating virus was surveyed to be the novel 2009 H1N1 influenza A according to the New York City Department of Health. We describe our experience using lung ultrasound in a case series of patients with respiratory symptoms requiring chest X-ray during the initial onset and surge of the 2009 H1N1 influenza pandemic. METHODS: We describe a case series of patients from a prospective observational cohort study of lung ultrasound, enrolling patients requiring chest X-ray for suspected pneumonia that coincided with the onset and surge of the 2009 H1N1 influenza pandemic. RESULTS: Twenty pandemic 2009 H1N1 influenza patients requiring chest X-ray were enrolled during this time period. Median age was 6.7 years. Lung ultrasound via modified Bedside Lung Ultrasound in Emergency protocol assisted in the identification of viral pneumonia (n = 15; 75%), viral pneumonia with superimposed bacterial pneumonia (n = 7; 35%), isolated bacterial pneumonia only (n = 1; 5%), and no findings of viral or bacterial pneumonia (n = 4; 20%) in this cohort of patients. Based on 54 observations, interobserver agreement for distinguishing viral from bacterial pneumonia using lung ultrasound was ĸ = 0.82 (0.63 to 0.99). CONCLUSIONS: Lung ultrasound may be used to distinguish viral from bacterial pneumonia. Lung ultrasound may be useful during epidemics or pandemics of acute respiratory illnesses for rapid point-of-care triage and management of patients. Emergency department visits quadrupled with the initial onset and surge during the 2009 H1N1 influenza pandemic in New York City (NYC) from April to June 2009 (Figures 1 and 2) [1, 2] . This time period was unique in that >90% of the circulating virus was surveyed to be the novel 2009 H1N1 influenza A according to the New York City Department of Health. Five-hundred sixtyseven patients requiring hospitalization were confirmed with the 2009 H1N1 influenza A in NYC [1] . In NYC, there were 16 deaths, 46% of admitted patients were <18 years old and 20% were <5 years old [2] . Eighty percent of confirmed cases had a known underlying risk condition, most commonly asthma (40% of confirmed cases) [1] .