Influenza Admissions Research Articles

Hospital-acquired influenza: Seek and ye shall find

BACKGROUND: In a 212-bed acute care community hospital that is part of a large academic teaching center in New York City, three inpatients acquired influenza A during their hospitalizations in December 2004. The first case was on a geriatric unit; the other two were on a telemetry unit. No hospital-acquired (HA) influenza cases had previously been described in this hospital. The New York City Department of Health had received no comparable reports from any other acute care facilities in the area. METHODS: All cases were diagnosed by nasopharyngeal swabs sent for enzyme immunoassay (EIA), direct fluorescent antibody (DFA), and viral culture. The first HA influenza patient was a readmission. As a result, another symptomatic inpatient was tested (positive). Surveillance testing was then performed and a third case was identified. The emergency department staff increased their testing for community-acquired (CA) influenza; patients presenting with fever over 100°F and respiratory symptoms were swabbed. Those being admitted were placed in single rooms on droplet isolation. Inpatients who spiked fevers and exhibited respiratory symptoms were swabbed and isolated. Positively identified influenza patients were cohorted and treated with amantadine or oseltamivir. Staff members exposed to non-isolated flu patients were given prophylaxis unless they had been vaccinated at least 2 weeks before. RESULTS: No more HA cases occurred. We were unable to identify sources for the three HA cases. Two of the three had received influenza vaccinations greater than 2 weeks before their admissions. The rate of CA influenza admissions rose from 0.45 per 100 admissions in December 2003, to 4.19 per 100 admissions in December 2004. Resources were stretched thin, including single rooms and surgical masks. CONCLUSION: A heightened degree of suspicion and testing led to the diagnosis of three HA cases of influenza and improved recognition of CA cases. This was especially important during a year of influenza vaccine shortage. Increased testing of symptomatic inpatients should be performed during influenza season to monitor for nosocomial transmission. BACKGROUND: In a 212-bed acute care community hospital that is part of a large academic teaching center in New York City, three inpatients acquired influenza A during their hospitalizations in December 2004. The first case was on a geriatric unit; the other two were on a telemetry unit. No hospital-acquired (HA) influenza cases had previously been described in this hospital. The New York City Department of Health had received no comparable reports from any other acute care facilities in the area. METHODS: All cases were diagnosed by nasopharyngeal swabs sent for enzyme immunoassay (EIA), direct fluorescent antibody (DFA), and viral culture. The first HA influenza patient was a readmission. As a result, another symptomatic inpatient was tested (positive). Surveillance testing was then performed and a third case was identified. The emergency department staff increased their testing for community-acquired (CA) influenza; patients presenting with fever over 100°F and respiratory symptoms were swabbed. Those being admitted were placed in single rooms on droplet isolation. Inpatients who spiked fevers and exhibited respiratory symptoms were swabbed and isolated. Positively identified influenza patients were cohorted and treated with amantadine or oseltamivir. Staff members exposed to non-isolated flu patients were given prophylaxis unless they had been vaccinated at least 2 weeks before. RESULTS: No more HA cases occurred. We were unable to identify sources for the three HA cases. Two of the three had received influenza vaccinations greater than 2 weeks before their admissions. The rate of CA influenza admissions rose from 0.45 per 100 admissions in December 2003, to 4.19 per 100 admissions in December 2004. Resources were stretched thin, including single rooms and surgical masks. CONCLUSION: A heightened degree of suspicion and testing led to the diagnosis of three HA cases of influenza and improved recognition of CA cases. This was especially important during a year of influenza vaccine shortage. Increased testing of symptomatic inpatients should be performed during influenza season to monitor for nosocomial transmission.

Epidemiology of Respiratory Infections in Young Children

The New Vaccine Surveillance Network, funded by the Centers for Disease Control and Prevention, was established to provide longitudinal data to help measure the impact of vaccines that decrease the burden of acute respiratory illness in children younger than 5 years of age. Currently 140,000 children younger than 5 years of age, nearly 1% of the U.S. population, are under surveillance in 3 urban counties, which include Nashville, TN, Rochester, NY, and Cincinnati, OH. Prospective, active, population-based surveillance of children hospitalized with respiratory symptoms or fever began in 2000, and outpatient surveillance began in 2002 in selected winter months. During the first year of surveillance, the admission rate for acute respiratory illness/fever in children younger than 5 years of age in the surveillance areas was 180 per 10,000 children. In 61% of these hospitalizations, a respiratory virus was identified. Respiratory syncytial viruses, influenza viruses and parainfluenza viruses were identified in 30%, and other respiratory viruses were identified in 36%. Approximately one-third of children hospitalized had identified high risk conditions, primarily asthma (24%). About one-half of the children hospitalized were younger than 6 months of age. Polymerase chain reaction doubled the diagnostic yield of culture for respiratory syncytial viruses, influenza and parainfluenza virus combined. Preliminary data on influenza admissions during the 4 years indicated considerable variation in admission rates by season and site. Annually the mean admission rates during the study period were 43 per 10,000 children younger than 6 months of age, 9 per 10,000 children 6-23 months of age and 4 per 10,000 children 24-59 months of age. These data provide ongoing surveillance of hospitalizations and other medically attended visits for respiratory viral illness in children younger than 5 years of age. Evaluation of influenza vaccine effectiveness, the epidemiology of respiratory viruses in children and the impact of the pediatric influenza vaccination program are in progress.

Effectiveness of influenza vaccine during pregnancy in preventing hospitalizations and outpatient visits for respiratory illness in pregnant women and their infants.

The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention recommends influenza vaccination for women who will be in the second or third trimester of pregnancy during the influenza season. We analyzed hospital admissions with principal diagnoses of influenza or pneumonia and influenza-like illness (ILI) outpatient visits to study the effectiveness of influenza vaccine during pregnancy in protecting women and infants from influenza-related morbidity. Estimates of influenza vaccine effectiveness across five flu seasons (Fall 1997 to Spring 2002) were calculated using Cox proportional hazards models for women and infant study populations in Kaiser Permanente Northern California. Outpatient utilization outcomes included physician visits with a diagnosis of upper respiratory infection, pharyngitis, otitis media, asthma, bronchial asthma, viral infection, pneumonia, fever, cough, or wheezing associated with respiratory illness. Inpatient outcomes included hospitalizations with principal diagnoses of influenza or pneumonia. Women who received influenza vaccine during pregnancy had the same risk for ILI visits compared with unvaccinated women, adjusting for women's age and week of delivery. When asthma visits were excluded from the outcome measure, we also found no difference in the risk of outpatient visits for vaccinated and unvaccinated women. Hospital admissions for influenza or pneumonia for women in the study population were quite rare and no women died of respiratory illness during pregnancy. Infants born to women who received influenza vaccination had the same risks for influenza or pneumonia admissions compared with infants born to unvaccinated women, adjusting for infant's gender, gestational age, week of birth, and birth facility. Maternal influenza vaccination was also not a significant determinant of risk of ILI (excluding otitis media) outpatient visits for infants, nor did it significantly affect the risk of otitis media visits. Influenza vaccination during pregnancy did not significantly affect the risk of cesarean section, adjusting for the woman's age. It also did not affect the risk of preterm delivery. Although the immunogenicity of influenza vaccination in pregnancy in mother and infant has been well documented, in this study, we were unable to demonstrate the effectiveness of influenza vaccination with data for hospital admissions and physician visits. One possible interpretation of these findings is that typical influenza surveillance measures based on utilization data are not reliable in distinguishing influenza from other respiratory illness. Hospitalizations for respiratory illness were uncommon in both vaccinees and nonvaccinees.

Additive preventive effect of influenza and pneumococcal vaccines in elderly persons.

In 1999, all individuals > or = 65 yrs of age (n=258,754) in Stockholm County, Sweden, were offered influenza and pneumococcal vaccination in a prospective study on the effectiveness of these vaccines in reducing the need for hospital treatment and death due to influenza, pneumonia and invasive pneumococcal disease (IPD). Data on hospitalisation and mortality during 1 yr were obtained from the administrative database in Stockholm County Council. Vaccination was performed in 124,702 (48%) subjects; 72,107 had both vaccines, 29,346 only had the influenza vaccine and 23,249 only had the pneumococcal vaccine. Compared with the unvaccinated cohort, a lower incidence of hospitalisation for all endpoint diagnoses was seen in vaccinated persons. An additive effectiveness of vaccination was seen when both vaccines were given, with a reduction of hospital admissions for influenza (37%), pneumonia (29%) and IPD (44%). In-hospital mortality for pneumonia was significantly lower in those who received both vaccines, than in unvaccinated persons. To conclude, vaccination with influenza and pneumococcal vaccines together was effective in reducing the need for hospital admission for influenza and pneumonia. There was a strong indication that pneumococcal vaccination alone, was effective not only in the prevention of invasive pneumococcal disease, but also of pneumonia overall, although to a low degree.

Influenza vaccination options to prevent hospitalization

Vaccination of children against influenza remains a controversial topic despite the substantial morbidity caused by this infection. To estimate the effect of three different vaccination strategies on preventing hospitalization due to influenza. A retrospective chart review was conducted of all children admitted to a tertiary health care centre who tested positive for influenza during three consecutive influenza seasons. The final analysis included 208 cases with an age range of five days to 16.1 years. Seventy-six children were considered 'high-risk' and 132 were considered 'previously healthy'. Length of stay (LOS) ranged from one day to 46 days with a mean of 6.3 days. The mean LOS was 8.6 days for children with risk factors and 4.9 days for those without risk factors. The number of preventable influenza admissions was determined over three years and averaged over one year for the three vaccination strategies. A universal strategy of vaccinating all previously healthy and high-risk children over six months of age would have prevented 118 admissions. Using a selective strategy of vaccinating only children over six months of age with risk factors and a third strategy of vaccinating only two- to six-month-old infants would have prevented 58 and 55 admissions, respectively. Use of the universal vaccination strategy would have prevented over one-half of the influenza admissions, which was over twice that of targeted vaccination. Until the challenges of implementing universal vaccination are fully understood, targeted vaccination remains an acceptable alternative.

Establishing thresholds for influenza surveillance in Victoria.

We aimed to review the proportion of influenza-like illness (ILI) that could be attributed to influenza infection over five consecutive influenza seasons in Victoria, to compare ILI activity with hospital admissions for influenza, and to develop thresholds that would indicate when ILI activity may coincide with increases in influenza hospitalizations. Combined nose/throat swabs from patients with ILI selected from sentinel general practices were tested for influenza and other respiratory viruses at the Victorian Infectious Diseases Reference Laboratory. The proportion of ILI attributed to laboratory-confirmed influenza was evaluated for five consecutive surveillance seasons, from 1998 to 2002. The seasonal patterns of ILI and laboratory-confirmed influenza were compared for 2000-02. ILI surveillance from sentinel general practices between 1997 and 2000 was compared with hospital admissions for influenza extracted from the Victorian Admitted Episodes Dataset between 1994 and 2000. Approximately 41% of all ILI cases from sentinel general practices were confirmed to have an influenza infection between 1998 and 2002. The seasonal pattern of ILI and confirmed influenza among patients selected from sentinel general practices was very similar over three influenza seasons. The trends for ILI rates in sentinel general practices appeared to correlate remarkably well with those of hospital admissions for influenza. Thresholds for ILI were defined as: baseline < 0.25 ILI cases/100 patients/week; normal seasonal activity 0.25-1.5; above normal seasonal activity > 1.5-3.5; and epidemic activity above 3.5. ILI rates from sentinel general practices correspond with hospital admissions coded as influenza and allow the use of threshold levels to describe seasonal influenza activity.

Influenza Pneumonia: A Descriptive Study

To describe the clinical features and complications of patients hospitalized with influenza during the 1999-2000 influenza season. We reviewed all cases of patients with influenza admitted to a large metropolitan referral hospital during the 1999-2000 season. Thirty-five adult patients (15 men and 20 women) tested positive for influenza A by direct enzyme immunoassay. A fourfold to sevenfold increase in the number of influenza cases was observed over previous years. Most patients had serious comorbid illnesses (88%), such as diabetes and chronic respiratory and heart disease. Seventeen patients developed pneumonia; these patients tended to be older (mean +/- SD, 63 +/- 13 years vs 51 +/- 19 years, respectively; p = 0.04) and had a higher incidence of chronic lung disease (41% vs 6%, respectively; p = 0.02) than the patients without pneumonia. Shortness of breath was the only symptom that distinguished patients with pneumonia from those with an upper respiratory tract illness alone. Antiviral treatment was begun 4 +/- 3 days from initiation of symptoms in patients with pneumonia and consisted of oseltamivir (35.2%), rimantadine (5.8%), or a combination of both (17.6%). Respiratory and/or blood culture results were positive in five patients (29%), Staphylococcus aureus was isolated in five patients, and Streptococcus pneumoniae was isolated in one patient. Ten of the patients with pneumonia (58.8%) were admitted to the ICU, and 5 patients (29%) died. The length of ICU stay and mechanical ventilation were 28 +/- 26 days and 21.5 +/- 20.5 days, respectively. Death in most pneumonia patients was attributed to respiratory failure. The recognized number of hospital admissions for influenza increased fourfold to sevenfold over previous years, most likely due to the implementation of rapid diagnostic tests for influenza. Patients with signs and symptoms of influenza and shortness of breath should undergo chest radiography. Hospitalization of patients with influenza pneumonia occurred in both previously healthy and immunocompromised patients and had a high mortality. S aureus was the most common bacterial isolate in patients with influenza pneumonia. Empiric antibiotics with staphylococcal activity should be used pending culture results in patients with influenza pneumonia. The effectiveness of oseltamivir and rimantadine in treating patients with influenza pneumonia remains to be determined.

Excess hospital admissions for pneumonia and influenza in persons [ges ]65 years associated with influenza epidemics in three English health districts: 1987–95

To study the association between community influenza activity and acute hospital admissions for pneumonia and influenza among elderly persons. Multiple regression analysis of acute hospital admissions against community influenza activity, air temperature and seasonal and long-term trends. Three English health districts: 1987-95. Persons aged > or = 65 years. Acute hospital admissions for pneumonia and influenza (ICD9: 480-487); excess hospital admissions during epidemic periods. The final regression model explained 70% of the total variation in hospital admissions for pneumonia and influenza, including 14% due to community influenza activity. However, most variation was explained by long-term and seasonal changes unrelated to influenza. In the large influenza epidemic of 1989/90 a typical health district (500,000 total population) experienced 56 excess admissions for pneumonia and influenza attributable to epidemic influenza among persons aged > or = 65 years, requiring 672 additional bed-days. However the figure varied widely between seasons and over the whole study period, the average winter excess was 17.5 admissions per health district, requiring an additional 210 bed-days. Influenza epidemics exert a variable impact on acute hospital admissions for pneumonia and influenza among elderly persons, which in the past have been poorly quantified. Although the absolute numbers of excess admissions is modest, their impact on bed availability may be considerable because of the duration of hospital stay in elderly persons.

Air pollution and hospital admissions for respiratory and cardiovascular diseases in Hong Kong.

OBJECTIVE: To investigate short term effects of concentrations of pollutants in ambient air on hospital admissions for cardiovascular and respiratory diseases in Hong Kong. METHODS: Retrospective ecological study. A Poisson...

Time-series analysis of the relation between influenza virus and hospital admissions of the elderly in Ontario, Canada, for pneumonia, chronic lung disease, and congestive heart failure.

This study examined the relation between the presence of circulating influenza virus and all hospital admissions of people over age 65 years in Ontario, Canada, for pneumonia, congestive heart failure, and chronic lung disease in 1988-1993. Autoregressive integrated moving average (ARIMA) transfer function models were used to perform a time-series analysis. These models were compared with simple cross correlations by using Pearson's product moment correlation. The results showed statistically significant correlations between the presence of influenza virus and admissions of the elderly for pneumonia (in all 5 years under study) and chronic lung disease (in 4 of the 5 years under study). The relation between circulation of influenza virus and admissions for congestive heart failure was inconsistent. The simple cross correlation tended to overestimate the association between the presence of circulating influenza strains and hospital admissions. Measures of the impact of influenza should include chronic lung disease as an outcome. Further studies, with greater covariate control, are required to delineate more precisely the relation between influenza and hospital morbidity in the elderly. This study demonstrates the power and utility of using time-series methods in the epidemiologic study of communicable diseases.

Effectiveness of influenza vaccine in reducing hospital admissions during the 1989–90 epidemic

The effectiveness of influenza vaccine in reducing hospital admissions for pneumonia, influenza, bronchitis, or emphysema was assessed by a case-control study of people aged 16 years and older who were admitted to 10 Leicestershire hospitals between 1 December 1989 and 31 January 1990. Hospital and general practitioners' records for 156 admissions (the cases) and 289 controls matched for age and sex were reviewed. Information was collected on demography, the usual place of residence (institutional or non-institutional), the existence of chronic illness, and vaccination during the 5 years before admission. The odds ratio for hospital admission among vaccinees was 0.67 (95% CI 0.39-1.12) giving an estimate of vaccine effectiveness in this setting of 33% (95% CI 0-61). However, multivariate logistic regression, adjusting for the effects of institutional care and chronic illness, revealed that influenza vaccination reduced hospital admissions by 63% (95% CI 17-84%). There was a strong trend towards improved vaccine effectiveness when used in institutional settings. Influenza vaccine is effective in reducing hospital admissions for influenza, pneumonia, bronchitis and emphysema, and effectiveness is comparable to that observed for influenza and pneumonia admissions in North America.