BACKGROUND: Young children are at increased risk of severe outcomes from influenza illness, including hospitalization. We conducted a case-control study to identify risk factors for influenza-associated hospitalizations among children in U.S. Emerging Infections Program sites. METHODS: Cases were children 6-59 months of age hospitalized for laboratory-confirmed influenza infections during 2005-08. Age- and zip-code-matched controls were enrolled. Data on child, caregiver, and household characteristics were collected from parents and medical records. Conditional logistic regression was used to identify independent risk factors for hospitalization. RESULTS: We enrolled 290 (64%) of 454 eligible cases and 1,089 (49%) of 2,204 eligible controls. Risk for influenza hospitalization increased with maternal age <26 years (odds ratio [OR] 1.8, 95% confidence interval [CI] 1.1-2.9); household income below the poverty threshold (OR 2.2, CI 1.4-3.6); smoking by >50% of household members (OR 2.9, CI 1.4-6.6); lack of household influenza vaccination (OR 1.8, CI 1.2-2.5); and presence of chronic illnesses, including hematologic/oncologic (OR 11.8, CI 4.5-31.0), pulmonary (OR 2.9, CI 1.9-4.4), and neurologic (OR 3.8, CI 1.6-9.2) conditions. Full influenza immunization decreased the risk among children aged 6-23 months (OR 0.5, CI 0.3-0.9) but not among those 24-59 months of age (OR 1.5, CI 0.8-3.0; p-value for difference = 0.01). CONCLUSIONS: Chronic illnesses, young maternal age, poverty, household smoking, and lack of household influenza vaccination increased the risk of influenza hospitalization. These characteristics may help providers to identify young children who are at greatest risk for severe outcomes from influenza illness.

BACKGROUND: Influenza-associated lower respiratory tract hemorrhage (LRTH) has been reported in previous pandemics and is a rare complication of seasonal influenza virus infection. We describe patients with LRTH associated with 2009 pandemic influenza A (H1N1) (pH1N1) virus infection identified from April 2009 to April 2010 in the United States. METHODS: We ascertained patients with pH1N1-associated LRTH through state and local surveillance, the Emerging Infections Program, and CDCs Infectious Diseases Pathology Branch. All patients had influenza A, evidence of pneumonia, and evidence of LRTH. Results We identified 44 cases; the median number of days from illness onset to clinical signs of LRTH was one. Hemoptysis or respiratory tract bleeding was documented in 40% of pH1N1-associated LRTH cases, often present early during the course of illness. Twenty-one (48%) patients with LRTH had no other hemorrhagic diatheses. Seven (23%) patients with LRTH received antiviral treatment within two days of illness onset. CONCLUSIONS: During influenza season, clinicians should consider influenza infection in the differential diagnosis for patients presenting with hemoptysis or other signs or symptoms of LRTH. While the impact of timing of antiviral therapy on this complication has not been studied, the rapid progression of LRTH may support use of early empiric therapy. Continued investigation is necessary to better define the clinical spectrum of both seasonal influenza- and pH1N1-associated LRTH.

OBJECTIVES: We assessed telephone surveys as a novel surveillance method, comparing data obtained by telephone with existing national influenza surveillance systems, and evaluated the utility of telephone surveys. METHODS: We used the 2007 Behavioral Risk Factor Surveillance System (BRFSS) and the 2007 National Immunization Survey-Adult (NIS-Adult) to estimate the incidence of influenza-like illness (ILI), medically attended ILI, provider-diagnosed influenza, influenza testing, and treatment of influenza with antiviral medications during the 2006-2007 influenza season. RESULTS: With the January-May BRFSS, among persons aged 18 years and older, the cumulative incidence of seasonal ILI and provider-diagnosed influenza was 37.9 and 5.7 adults per 100 persons, respectively. Monthly medically attended ILI and provider-diagnosed influenza among adults were temporally associated with influenza activity, as documented by national surveillance. With the NIS-Adult survey data, estimated provider-diagnosed influenza, influenza testing, and antiviral treatment were 2.8%, 1.4%, and 0.6%, respectively. CONCLUSIONS: Our telephone interview-based estimates of influenza morbidity were consistent with those from national influenza surveillance systems. Telephone surveys may provide an alternative method by which population-based influenza morbidity information can be gathered. (Am J Public Health. Published online ahead of print December 13, 2012: e1-e9. doi:10.2105/AJPH.2012.300799).

OBJECTIVES: The purpose of our study was to more accurately characterize people reporting influenza-like illness (ILI) and evaluate trends in health care seeking and influenza diagnosis and treatment during the 2009 influenza pandemic. METHODS: From September 2009 to March 2010, we ascertained ILI (fever with cough or sore throat), health care seeking, and clinical diagnosis and treatment of influenza with influenza antiviral drugs among adults in 51 jurisdictions, and ILI and health care seeking among children in 41 jurisdictions. RESULTS: Among 216,431 adults and 43,511 children, 8.1% and 28.4% reported ILI, respectively. ILI peaked during November interviews and was higher among young people and American Indian/Alaska Natives. Of those with ILI, 40% of adults and 56% of children reported seeking health care; 26% of adults who sought care reported receiving a diagnosis of influenza. Of adults reporting an influenza diagnosis, 36% were treated with influenza antiviral drugs; treatment was highest among adults aged 18 to 49 years. CONCLUSIONS: Analysis of ILI data from the Behavioral Risk Factor Surveillance System enabled a better understanding of the factors associated with self-reported ILI, health care seeking, and clinical influenza diagnosis and treatment, and will help inform year-to-year influenza trends. (Am J Public Health. Published online ahead of print August 16, 2012: e1-e6. doi:10.2105/AJPH.2012.300651).

BACKGROUND: The influenza A (H1N1pdm09) [pH1N1] virus resulted in intensive care unit (ICU) admissions, acute respiratory distress syndrome (ARDS), and death. OBJECTIVES: To describe the characteristics of ICU patients with pH1N1 virus infection in the United States during the spring and fall of 2009 and to describe the factors associated with severe complications including ARDS and death. PATIENTS/METHODS: Through two national case-series conducted during spring and fall of 2009, medical charts were reviewed on ICU patients with laboratory-confirmed pH1N1 infection by real-time reverse-transcriptase polymerase chain reaction. RESULTS: The majority (77%) of 154 patients hospitalized in an ICU were <50 years of age, and 65% had at least one underlying medical condition. One hundred and twenty-eight (83%) patients received influenza antiviral agents; 29% received treatment ≤2 days after illness onset. Forty-eight (38%) patients developed ARDS and 37 (24%) died. Patients with ARDS were more likely to be morbidly obese (36% versus 19%, P = 0.04) and patients who died were less likely to have asthma (11% versus 28%, P = 0.05). Compared with patients who received treatment ≥6 days after illness onset, patients treated ≤2 days after illness onset were less likely to develop ARDS (17% versus 37%, P < 0.01) or die (7% versus 35%, P < 0.01). CONCLUSIONS: Among patients hospitalized in an ICU with pH1N1 virus infection, ARDS was a common complication, and one-quarter of patients died. Patients with asthma had less severe outcomes. Early treatment with influenza antiviral agents was likely beneficial, especially when initiated ≤2 days after illness onset.

BACKGROUND: Statins may have anti-inflammatory and immunomodulatory effects that could reduce the risk of mortality from influenza virus infections. METHODS: The Centers for Disease Control and Prevention's Emerging Infections Program conducts active surveillance for persons hospitalized with laboratory-confirmed influenza in 59 counties in 10 states. We analyzed data for hospitalized adults during the 2007-2008 influenza season to evaluate the association between receiving statins and influenza-related death. RESULTS: We identified 3043 patients hospitalized with laboratory-confirmed influenza, of whom 1013 (33.3%) received statins and 151 (5.0%) died within 30 days of their influenza test. Patients who received statins were more likely to be older, male, and white; to suffer from cardiovascular, metabolic, renal, and chronic lung disease; and to have been vaccinated against influenza that season. In a multivariable logistic regression model, administration of statins prior to or during hospitalization was associated with a protective odds of death (adjusted odds ratio, 0.59 [95% confidence interval, .38-.92]) when adjusting for age; race; cardiovascular, lung, and renal disease; influenza vaccination; and antiviral administration. CONCLUSIONS: Statin use may be associated with reduced mortality in patients hospitalized with influenza.

BACKGROUND: The 2009 influenza pandemic led to guidelines emphasizing antiviral treatment for all persons hospitalized with influenza, including pregnant women. We compared antiviral use among adults hospitalized with influenza before and during the pandemic. METHODS: The Emerging Infections Program conducts active population-based surveillance for persons hospitalized with community-acquired, laboratory-confirmed influenza in 10 states. We analyzed data collected via medical record review of patients aged ≥18 years admitted during prepandemic (1 October 2005 through 14 April 2009) and pandemic (15 April 2009 through 31 December 2009) time frames. RESULTS: Of 5943 adults hospitalized with influenza in prepandemic seasons, 3235 (54%) received antiviral treatment, compared with 4055 (82%) of 4966 during the pandemic. Forty-one (22%) of 187 pregnant women received antiviral treatment in prepandemic seasons, compared with 369 (86%) of 430 during the pandemic. Pregnancy was a negative predictor of antiviral treatment before the pandemic (adjusted odds ratio [aOR], 0.24; 95% confidence interval [CI], .16-.35) but was independently associated with treatment during the pandemic (aOR, 1.97; 95% CI, 1.32-2.96). Antiviral treatment among adults hospitalized >2 days after illness onset increased from 43% before the pandemic to 79% during the pandemic (P < .001). CONCLUSIONS: Antiviral treatment of hospitalized adults increased during the pandemic, especially among pregnant women. This suggests that many clinicians followed published guidance to treat hospitalized adults with antiviral agents. However, compliance with antiviral recommendations could be improved.

PURPOSE: Concerns have been raised regarding possible racial-ethnic disparities in 2009 pandemic influenza A (H1N1) (pH1N1) illness severity and health consequences for U.S. minority populations. METHODS: Using data from the Centers for Disease Control and Prevention's Behavioral Risk Factor Surveillance System, Emerging Infections Program Influenza-Associated Hospitalization Surveillance, and Influenza-Associated Pediatric Mortality Surveillance, we calculated race-ethnicity-specific, age-adjusted rates of self-reported influenza-like illness (ILI) and pH1N1-associated hospitalizations. We used chi(2) tests to evaluate racial-ethnic disparities in ILI-associated health care-seeking behavior and pH1N1 hospitalization. To evaluate pediatric deaths, we compared racial-ethnic proportions of deaths against U.S. population distributions. RESULTS: Prevalence of self-reported ILI was lower among Hispanics (6.5%), higher among American Indians/Alaska Natives (16.2%), and similar among non-Hispanic blacks (7.7%) compared with non-Hispanic whites (8.5%). No racial-ethnic differences were identified in ILI-associated health care-seeking behavior. Age-adjusted pH1N1-associated Emerging Infections Program hospitalization rates were higher among all minority populations (range: 8.1-10.9/100,000 population) compared with non-Hispanic whites (3.0/100,000). The proportion of pH1N1-associated pediatric deaths was higher than expected among Hispanics (31%) and lower than expected among non-Hispanic whites (45%) given the proportions of the U.S. population they comprise (22% and 58%, respectively). CONCLUSIONS: Racial-ethnic disparities in pH1N1-associated hospitalizations and pediatric deaths were identified. Vaccination remains the primary intervention for preventing influenza.

BACKGROUND: Evidence is needed on the effectiveness of non-pharmaceutical interventions (NPIs) to reduce influenza transmission. METHODOLOGY: We studied NPIs in households with a febrile, influenza-positive child. Households were randomized to control, hand washing (HW), or hand washing plus paper surgical face masks (HW + FM) arms. Study nurses conducted home visits within 24 hours of enrollment and on days 3, 7, and 21. Respiratory swabs and serum were collected from all household members and tested for influenza by RT-PCR or serology. PRINCIPAL FINDINGS: Between April 2008 and August 2009, 991 (16.5%) of 5995 pediatric influenza-like illness patients tested influenza positive. Four hundred and forty-two index children with 1147 household members were enrolled, and 221 (50.0%) were aged <6 years. Three hundred and ninety-seven (89.8%) households reported that the index patient slept in the parents' bedroom. The secondary attack rate was 21.5%, and 56/345 (16.3%; 95% CI 12.4-20.2%) secondary cases were asymptomatic. Hand-washing subjects reported 4.7 washing episodes/day, compared to 4.9 times/day in the HW + FM arm and 3.9 times/day in controls (P = 0.001). The odds ratios (ORs) for secondary influenza infection were not significantly different in the HW arm (OR = 1.20; 95% CI 0.76-1.88; P-0.442), or the HW + FM arm (OR = 1.16; 95% CI .0.74-1.82; P = 0.525). CONCLUSIONS: Influenza transmission was not reduced by interventions to promote hand washing and face mask use. This may be attributable to transmission that occurred before the intervention, poor facemask compliance, little difference in hand-washing frequency between study groups, and shared sleeping arrangements. A prospective study design and a careful analysis of sociocultural factors could improve future NPI studies.

OBJECTIVE: To describe the characteristics and clinical courses of asthmatic children hospitalized with seasonal or 2009 pandemic H1N1 influenza and compare complications by influenza type. METHODS: During the 2003-2009 influenza seasons and the 2009 pandemic, we conducted surveillance of 5.3 million children aged 17 years or younger for hospitalization with laboratory-confirmed influenza and identified those with asthma (defined as those aged 2-17 years with a history of asthma in their medical record or a discharge code for acute asthma exacerbation or status asthmaticus). We collected data from medical records on medical history and clinical course; data on asthma severity and control were not routinely collected. RESULTS: During the 2003-2009 influenza seasons, 701 (32%) of 2165 children hospitalized with influenza had asthma; during the 2009 pandemic, 733 (44%) of 1660 children had asthma. The median age of the asthmatic children was 7 years, and 73% had no additional medical conditions. Compared with asthmatic children with seasonal influenza, a higher proportion with 2009 pandemic H1N1 influenza required intensive care (16% vs 22%; P = .01) and were diagnosed with pneumonia (40% vs 46%; P = .04), whereas equal proportions had respiratory failure (5% vs 5%; P = .8) and died (1% vs 1%; P = .4). More asthmatic children with influenza A (seasonal or pandemic) had diagnoses of asthma exacerbations compared with those with influenza B (51% vs 29%; P < .01). CONCLUSIONS: The majority of asthmatic children hospitalized with influenza have no additional medical conditions. Complications such as pneumonia and need for intensive care occur in a substantial proportion, highlighting the importance of influenza prevention through vaccination among asthmatic children.

We sought to describe characteristics of hospitalized reproductive-aged (15-44 years) women with seasonal (2005/2006 through 2008/2009) and 2009 pandemic influenza A (H1N1) virus infection. We used population-based data from the Emerging Infections Program in 10 US states, and compared characteristics of pregnant (n = 150) and nonpregnant (n = 489) seasonal, and pregnant (n = 489) and nonpregnant (n = 1088) pandemic influenza cases using chi(2) and Fisher's exact tests. Pregnant women represented 23.5% and 31.0% of all reproductive-aged women hospitalized for seasonal and pandemic influenza, respectively. Significantly more nonpregnant than pregnant women with seasonal (71.2% vs 36.0%) and pandemic (69.7% vs 31.9%) influenza had an underlying medical condition other than pregnancy. Antiviral treatment was significantly more common with pandemic than seasonal influenza for both pregnant (86.5% vs 24.0%) and nonpregnant (82.0% vs 55.2%) women. Pregnant women comprised a significant proportion of influenza-hospitalized reproductive-aged women, underscoring the importance of influenza vaccination during pregnancy.

During April 2009-June 2010, thirty-seven (0.5%) of 6,740 pandemic (H1N1) 2009 viruses submitted to a US surveillance system were oseltamivir resistant. Most patients with oseltamivir-resistant infections were severely immunocompromised (76%) and had received oseltamivir before specimen collection (89%). No evidence was found for community circulation of resistant viruses; only 4 (unlinked) patients had no oseltamivir exposure.

A critical issue during the 2009 influenza A (H1N1) pandemic was determining the appropriate duration of time individuals with influenza-like illness (ILI) should remain isolated to reduce onward transmission while limiting societal disruption. Ideally this is based on knowledge of the relative infectiousness of ill individuals at each point during the course of the infection. Data on 261 clinically apparent pH1N1 infector-infectee pairs in households, from 7 epidemiological studies conducted in the United States early in 2009, were analyzed to estimate the distribution of times from symptom onset in an infector to symptom onset in the household contacts they infect (mean, 2.9 days, not correcting for tertiary transmission). Only 5% of transmission events were estimated to take place .3 days after the onset of clinical symptoms among those ill with pH1N1 virus. These results will inform future recommendations on duration of isolation of individuals with ILI.

The emergence in April 2009 and subsequent spread of the 2009 pandemic influenza A (H1N1) virus resulted in the first pandemic of the 21st century. This historic event was associated with unusual patterns of influenza activity in terms of the timing and persons affected in the United States throughout the summer and fall months of 2009 and the winter of 2010. The US Influenza Surveillance System identified 2 distinct waves of pandemic influenza H1N1 activity - the first peaking in June 2009, followed by a second peak in October 2009. All influenza surveillance components showed levels of influenza activity above that typically seen during late summer and early fall. During this period, influenza activity reached its highest level during the week ending 24 October 2009. This report summarizes US influenza surveillance data from 12 April 2009 through 27 March 2010.

In April 2009, the Centers for Disease Control and Prevention confirmed 2 cases of 2009 pandemic influenza A (H1N1) virus infection in children from southern California, marking the beginning of what would be the first influenza pandemic of the twenty-first century. This report describes the epidemiology of the 2009 H1N1 pandemic in the United States, including characterization of cases, fluctuations of disease burden over the course of a year, the age distribution of illness and severe outcomes, and estimation of the overall burden of disease.

To calculate the burden of 2009 pandemic influenza A (pH1N1) in the United States, we extrapolated from the Centers for Disease Control and Prevention's Emerging Infections Program laboratory-confirmed hospitalizations across the entire United States, and then corrected for underreporting. From 12 April 2009 to 10 April 2010, we estimate that approximately 60.8 million cases (range: 43.3-89.3 million), 274,304 hospitalizations (195,086-402,719), and 12,469 deaths (8,868-18,306) occurred in the United States due to pH1N1. Eighty-seven percent of deaths occurred in those under 65 years of age with children and working adults having risks of hospitalization and death 4 to 7 times and 8 to 12 times greater, respectively, than estimates of impact due to seasonal influenza covering the years 1976-2001. In our study, adults 65 years of age or older were found to have rates of hospitalization and death that were up to 75% and 81%, respectively, lower than seasonal influenza. These results confirm the necessity of a concerted public health response to pH1N1.

BACKGROUND: Rates of influenza-associated hospitalizations in the United States have been estimated using modeling techniques with data from pneumonia and influenza hospitalization discharge diagnoses, but they have not been directly estimated from laboratory-positive cases. METHODS: We calculated overall, age-specific, and site-specific rates of laboratory-positive, influenza-associated hospitalization among adults and compared demographic and clinical characteristics and outcomes of hospitalized cases by season with use of data collected by the Emerging Infections Program Network during the 2005-2006 through 2007-2008 influenza seasons. RESULTS: Overall rates of adult influenza-associated hospitalization per 100,000 persons were 9.9 during the 2005-2006 season, 4.8 during the 2006-2007 season, and 18.7 during the 2007-2008 season. Rates of hospitalization varied by Emerging Infections Program site and increased with increasing age. Higher overall and age-specific rates of hospitalization were observed during influenza A (H3) predominant seasons and during periods of increased circulation of influenza B. More than 80% of hospitalized persons each season had 1 underlying medical condition, including chronic cardiovascular and metabolic diseases. CONCLUSIONS: Rates varied by season, age, geographic location, and type/subtype of circulating influenza viruses. Influenza-associated hospitalization surveillance is essential for assessing the relative severity of influenza seasons over time and the burden of influenza-associated complications.

OBJECTIVES: To estimate the rates of hospitalization with seasonal influenza in children aged <18 years from a large, diverse surveillance area during 2003 to 2008. STUDY DESIGN: Through the Emerging Infections Program Network, population-based surveillance for laboratory-confirmed influenza was conducted in 10 states, including 5.3 million children. Hospitalized children were identified retrospectively; clinicians made influenza testing decisions. Data collected from the hospital record included demographics, medical history, and clinical course. Incidence rates were calculated with census data. RESULTS: The highest hospitalization rates occurred in children aged <6 months (seasonal range, 9-30/10 000 children), and the lowest rates occurred in children aged 5 to 17 years (0.3-0.8/10 000). Overall, 4015 children were hospitalized, 58% of whom were identified with rapid diagnostic tests alone. Forty percent of the children who were hospitalized had underlying medical conditions; asthma (18%), prematurity (15% of children aged <2 years), and developmental delay (7%) were the most common. Severe outcomes included intensive care unit admission (12%), respiratory failure (5%), bacterial coinfection (2%), and death (0.5%). CONCLUSIONS: Influenza-associated hospitalization rates varied by season and age and likely underestimate true rates because many hospitalized children are not tested for influenza. The proportion of children with severe outcomes was substantial across seasons. Quantifying incidence of influenza hospitalization and severe outcomes is critical to defining disease burden.

BACKGROUND: Pneumonia is one of the most common complications in children hospitalized with influenza. We describe hospitalized children with influenza-associated pneumonia and associated risk indicators. METHODS: Through Emerging Infections Program Network population based surveillance, children aged <18 years hospitalized with laboratory confirmed influenza with a chest radiograph during hospitalization were identified during the 2003-2008 influenza seasons. A case with radiologically confirmed influenza-associated pneumonia was defined as a child from the surveillance area hospitalized with: (1) laboratory-confirmed influenza and (2) evidence of new pneumonia on chest radiograph during hospitalization. Hospitalized children with pneumonia were compared with those without pneumonia by univariate and multivariate analysis. RESULTS: Overall, 2992 hospitalized children with influenza with a chest radiograph were identified; 1072 (36%) had influenza-associated pneumonia.When compared with children hospitalized with influenza without pneumonia, hospitalized children with influenza-associated pneumonia were more likely to require intensive care unit admission (21% vs. 11%, P < 0.01), develop respiratory failure (11% versus 3%, P < 0.01), and die(0.9% vs. 0.3% P 0.01). In multivariate analysis, age 6 to 23 months(adjusted OR: 2.1, CI: 1.6 -2.8), age 2 to 4 years (adjusted OR: 1.7, CI:1.3-2.2), and asthma (adjusted OR: 1.4, CI: 1.1-1.8) were significantly associated with influenza-associated pneumonia. CONCLUSIONS: Hospitalized children with influenza-associated pneumonia were more likely to have a severe clinical course than other hospitalized children with influenza, and children aged 6 months to 4 years and those with asthma were more likely to have influenza-associated pneumonia. Identifying children at greater risk for influenza-associated pneumonia will inform prevention and treatment strategies targeting children at risk for influenza complications.

BACKGROUND: Severe illness due to 2009 pandemic A(H1N1) infection has been reported among persons who are obese or morbidly obese. We assessed whether obesity is a risk factor for hospitalization and death due to 2009 pandemic influenza A(H1N1), independent of chronic medical conditions considered by the Advisory Committee on Immunization Practices (ACIP) to increase the risk of influenza-related complications. METHODOLOGY/PRINCIPAL FINDINGS: We used a case-cohort design to compare cases of hospitalizations and deaths from 2009 pandemic A(H1N1) influenza occurring between April-July, 2009, with a cohort of the U.S. population estimated from the 2003-2006 National Health and Nutrition Examination Survey (NHANES); pregnant women and children <2 years old were excluded. For hospitalizations, we defined categories of relative weight by body mass index (BMI, kg/m(2)); for deaths, obesity or morbid obesity was recorded on medical charts, and death certificates. Odds ratio (OR) of being in each BMI category was determined; normal weight was the reference category. Overall, 361 hospitalizations and 233 deaths included information to determine BMI category and presence of ACIP-recognized medical conditions. Among >or=20 year olds, hospitalization was associated with being morbidly obese (BMI>or=40) for individuals with ACIP-recognized chronic conditions (OR = 4.9, 95% CI 2.4-9.9) and without ACIP-recognized chronic conditions (OR = 4.7, 95%CI 1.3-17.2). Among 2-19 year olds, hospitalization was associated with being underweight (BMI<or=5(th) percentile) among those with (OR = 12.5, 95%CI 3.4-45.5) and without (OR = 5.5, 95%CI 1.3-22.5) ACIP-recognized chronic conditions. Death was not associated with BMI category among individuals 2-19 years old. Among individuals aged >or=20 years without ACIP-recognized chronic medical conditions death was associated with obesity (OR = 3.1, 95%CI: 1.5-6.6) and morbid obesity (OR = 7.6, 95%CI 2.1-27.9). CONCLUSIONS/SIGNIFICANCE: Our findings support observations that morbid obesity may be associated with hospitalization and possibly death due to 2009 pandemic H1N1 infection. These complications could be prevented by early antiviral therapy and vaccination.

STUDY OBJECTIVE: Influenza causes significant widespread illness each year. Emergency department (ED) clinicians are often first-line providers to evaluate and make treatment decisions for patients presenting with influenza. We sought to better understand ED clinician testing and treatment practices in the Emerging Infections Program Network, a federal, state, and academic collaboration that conducts active surveillance for influenza-associated hospitalizations. METHODS: During 2007, a survey was administered to ED clinicians who worked in Emerging Infections Program catchment area hospitals' EDs. The survey encompassed the role of the clinician, years since completing clinical training, hospital type, influenza testing practices, and use of antiviral medications during the 2006 to 2007 influenza season. We examined factors associated with influenza testing and antiviral use. RESULTS: A total of 1,055 ED clinicians from 123 hospitals responded to the survey. A majority of respondents (85.3%; n=887) reported they had tested their patients for influenza during the 2006 to 2007 influenza season (Emerging Infections Program site range: 59.3 to 100%; P<.0001). When asked about antiviral medications, 55.7% (n=576) of respondents stated they had prescribed antiviral medications to some of their patients in 2006 to 2007 (Emerging Infections Program site range 32.9% to 80.3%; P<.0001). A positive association between influenza testing and prescribing antiviral medications was observed. Additionally, the type of hospital, location in which an ED clinician worked, and the number of years since medical training were associated with prescribing antiviral influenza medications. CONCLUSION: There is much heterogeneity in clinician-initiated influenza testing and treatment practices. Additional exploration of the role of hospital testing and treatment policies, clinicians' perception of influenza disease, and methods for educating clinicians about new recommendations is needed to better understand ED clinician testing and treatment decisions, especially in an environment of rapidly changing influenza clinical guidelines. Until influenza testing and treatment guidelines are better promulgated, clinicians may continue to test and treat influenza with inconsistency.

BACKGROUND: During the spring of 2009, a pandemic influenza A (H1N1) virus emerged and spread globally. We describe the clinical characteristics of patients who were hospitalized with 2009 H1N1 influenza in the United States from April 2009 to mid-June 2009. METHODS: Using medical charts, we collected data on 272 patients who were hospitalized for at least 24 hours for influenza-like illness and who tested positive for the 2009 H1N1 virus with the use of a real-time reverse-transcriptase-polymerase-chain-reaction assay. RESULTS: Of the 272 patients we studied, 25% were admitted to an intensive care unit and 7% died. Forty-five percent of the patients were children under the age of 18 years, and 5% were 65 years of age or older. Seventy-three percent of the patients had at least one underlying medical condition; these conditions included asthma; diabetes; heart, lung, and neurologic diseases; and pregnancy. Of the 249 patients who underwent chest radiography on admission, 100 (40%) had findings consistent with pneumonia. Of the 268 patients for whom data were available regarding the use of antiviral drugs, such therapy was initiated in 200 patients (75%) at a median of 3 days after the onset of illness. Data suggest that the use of antiviral drugs was beneficial in hospitalized patients, especially when such therapy was initiated early. CONCLUSIONS: During the evaluation period, 2009 H1N1 influenza caused severe illness requiring hospitalization, including pneumonia and death. Nearly three quarters of the patients had one or more underlying medical conditions. Few severe illnesses were reported among persons 65 years of age or older. Patients seemed to benefit from antiviral therapy.