Incidence and viral aetiologies of acute respiratory illnesses (ARIs) in the United States: a population-based study.

We conducted prospective, community-wide surveillance for acute respiratory illnesses (ARIs) in Rochester, NY and Marshfield, WI during a 3-month period in winter 2011. We estimated the incidence of ARIs in each community, tested for viruses, and determined the proportion of ARIs associated with healthcare visits. We used a rolling cross-sectional design to sample participants, conducted telephone interviews to assess ARI symptoms (defined as a current illness with feverishness or cough within the past 7 days), collected nasal/throat swabs to identify viruses, and extracted healthcare utilization from outpatient/inpatient records. Of 6492 individuals, 321 reported an ARI within 7 days (4·9% total, 5·7% in Rochester, 4·4% in Marshfield); swabs were collected from 208 subjects. The cumulative ARI incidence for the entire 3-month period was 52% in Rochester [95% confidence interval (CI) 42-63] and 35% in Marshfield (95% CI 28-42). A specific virus was identified in 39% of specimens: human coronavirus (13% of samples), rhinovirus (12%), RSV (7%), influenza virus (4%), human metapneumovirus (4%), and adenovirus (1%). Only 39/200 (20%) had a healthcare visit (2/9 individuals with influenza). ARI incidence was ~5% per week during winter.

A probability model for evaluating the bias and precision of influenza vaccine effectiveness estimates from case-control studies.

As influenza vaccination is now widely recommended, randomized clinical trials are no longer ethical in many populations. Therefore, observational studies on patients seeking medical care for acute respiratory illnesses (ARIs) are a popular option for estimating influenza vaccine effectiveness (VE). We developed a probability model for evaluating and comparing bias and precision of estimates of VE against symptomatic influenza from two commonly used case-control study designs: the test-negative design and the traditional case-control design. We show that when vaccination does not affect the probability of developing non-influenza ARI then VE estimates from test-negative design studies are unbiased even if vaccinees and non-vaccinees have different probabilities of seeking medical care against ARI, as long as the ratio of these probabilities is the same for illnesses resulting from influenza and non-influenza infections. Our numerical results suggest that in general, estimates from the test-negative design have smaller bias compared to estimates from the traditional case-control design as long as the probability of non-influenza ARI is similar among vaccinated and unvaccinated individuals. We did not find consistent differences between the standard errors of the estimates from the two study designs.

Influenza-associated excess mortality in southern Brazil, 1980-2008.

In order to estimate influenza-associated excess mortality in southern Brazil, we applied Serfling regression models to monthly mortality data from 1980 to 2008 for pneumonia/influenza- and respiratory/circulatory-coded deaths for all ages and for those aged ≥60 years. According to viral data, 73∙5% of influenza viruses were detected between April and August in southern Brazil. There was no clear influenza season for northern Brazil. In southern Brazil, influenza-associated excess mortality was 1∙4/100,000 for all ages and 9∙2/100,000 person-years for persons aged ≥60 years using underlying pneumonia/influenza-coded deaths and 10∙0/100,000 for all ages and 86∙6/100,000 person-years for persons aged ≥60 years using underlying respiratory/circulatory-coded deaths. Influenza-associated excess mortality rates for southern Brazil are similar to those published for other countries. Our data support the need for continued influenza surveillance to guide vaccination campaigns to age groups most affected by this virus in Brazil.

Association between obesity and vulnerability and serologic response to influenza vaccination in older adults.

BACKGROUND: Serologic response to influenza vaccination declines with age. Few other host factors are known to be associated with serologic response. Our objective was to determine whether obesity and vulnerability independently predicted serologic response to influenza vaccination. METHODS: Adults ≥ 50 years were recruited during the 2008-2009 influenza season. Subjects provided pre- and post-vaccination sera for measuring antibody titers to 2008-2009 vaccine components. Body mass index (BMI) was calculated as weight (kg)/height (m(2)). Data were collected on vulnerability using the vulnerable elders survey (VES13). Logistic regression evaluated the associations between obesity and vulnerability and the serologic response to vaccination (both seroprotection and seroconversion), adjusting for gender, age, comorbidities, pre-vaccination titer, and site. RESULTS: Mean (± standard deviation) age of 415 study subjects was 65 ± 10 years; 40% were obese. Mean BMI was 29 ± 5.6 kg/m(2); mean VES13 was 1.6 ± 1.8. The proportions of subjects who seroconverted and had seroprotective titers were 40% and 49%, respectively, for A/Brisbane/59 (H1N1); 73% and 80% for A/Brisbane/10 (H3N2); and 34% and 94% for B/Florida. Modified VES-13 (score 0-10, with 10 being most vulnerable) was not associated with seroprotection against H1N1 or H3N2, and VES-13 was directly associated with seroconversion to H1N1 but not H3N2 or B. Obesity (BMI ≥ 30 kg/m(2) vs. BMI 18.5-30 kg/m(2)) was not associated with seroprotection for H1N1 or H3N2; obesity was directly associated with seroconversion to H3N2 but not H1N1 or B. Age was inversely associated with seroprotection and seroconversion against H1N1 and with seroconversion to influenza B. CONCLUSION: Based on this sample of older healthy subjects, there were no consistent relationships between VES 13 or obesity and either seroprotection or seroconversion to three influenza vaccine antigens.

Is household antibiotic use a risk factor for antibiotic-resistant pneumococcal infection?

We used microbiology and pharmacy data from health-maintenance organizations to determine whether antibiotic use by a household member increases the risk of penicillin-non-susceptible pneumococcal disease. Though it has been well established that an individual's antibiotic use increases one's risk of antibiotic-resistant infection, it is unclear whether the risk is increased if a member of one's household is exposed to antibiotics. We therefore conducted a case-control study of patients enrolled in health maintenance organizations in Western Washington and Northern California. Cases were defined as individuals with penicillin-non-susceptible pneumococcal infection; controls were individuals with penicillin-susceptible pneumococcal infection. Socioeconomic variables were obtained by linking addresses with 1997 census block group data. One-hundred and thirty-four cases were compared with 798 controls. Individual antibiotic use prior to diagnosis increased the odds of penicillin non-susceptibility, with the strongest effect seen for beta-lactam use within 2 months (OR 1.8, 95% CI 1.2, 2.8). When household antibiotic use by persons other than the patient were considered, at 4 months prior to diagnosis there was a trend towards an association between penicillin non-susceptibility and beta-lactam antibiotic use, and a possible association in a small subgroup of patients with eye and ear isolates. However, no significant overall pattern of association was seen. We conclude that though antibiotic use of any kind within 2 months prior to diagnosis is associated with an increased risk of penicillin-non-susceptible pneumococcal disease, there is no significant overall pattern of association between household antibiotic use and penicillin-non-susceptible pneumococcal infection.

Costs and savings associated with infection control measures that reduced transmission of vancomycin-resistant enterococci in an endemic setting.

OBJECTIVE: To determine the costs and savings of a 15-component infection control program that reduced transmission of vancomycin-resistant enterococci (VRE) in an endemic setting. DESIGN: Evaluation of costs and savings, using historical control data. SETTING: Adult oncology unit of a 650-bed hospital. PARTICIPANTS: Patients with leukemia, lymphoma, and solid tumors, excluding bone marrow transplant recipients. METHODS: Costs and savings with estimated ranges were calculated. Excess length of stay (LOS) associated with VRE bloodstream infection (BSI) was determined by matching VRE BSI patients with VRE-negative patients by oncology diagnosis. Differences in LOS between the matched groups were evaluated using a mixed-effect analysis of variance linear-regression model. RESULTS: The cost of enhanced infection control strategies for 1 year was $116,515. VRE BSI was associated with an increased LOS of 13.7 days. The savings associated with fewer VRE BSI ($123,081), fewer patients with VRE colonization ($2,755), and reductions in antimicrobial use ($179,997) totaled $305,833. Estimated ranges of costs and savings for enhanced infection control strategies were $97,939 to $148,883 for costs and $271,531 to $421,461 for savings. CONCLUSION: The net savings due to enhanced infection control strategies for 1 year was $189,318. Estimates suggest that these strategies would be cost-beneficial for hospital units where the number of patients with VRE BSI is at least six to nine patients per year or if the savings from fewer VRE BSI patients in combination with decreased antimicrobial use equalled $100,000 to $150,000 per year.

Human parainfluenza virus-associated hospitalizations among children less than five years of age in the United States.

BACKGROUND: Human parainfluenza viruses 1 through 3 (HPIV-1-3) are important causes of respiratory tract infections in young children. This study sought to provide current estimates of HPIV-1-3-associated hospitalizations among US children. METHODS: Hospitalizations for bronchiolitis, bronchitis, croup and pneumonia among children age <5 years were determined for the years 1979 through 1997 using the National Hospital Discharge Survey. Average annual hospitalizations during the last 4 years of the study for each of these four diseases were multiplied by the proportions of each disease associated with HPIV-1-3 infection (as previously reported in hospital-based studies) to estimate hospitalizations potentially associated with HPIV-1-3 infections. Seasonal trends in HPIV-1-3-associated hospitalizations were compared with HPIV detections in the National Respiratory and Enteric Virus Surveillance System, which prospectively monitors respiratory viral detections throughout the United States. RESULTS: The proportions of hospitalizations associated with HPIV infection for each disease varied widely in the 6 hospital-based studies we selected. Consequently our annual estimated rates of hospitalization were broad: HPIV-1, 0.32 to 1.59 per 1,000 children; HPIV-2, 0.10 to 0.86 per 1,000 children; and HPIV-3, 0.48 to 2.6 per 1,000 children. Based on these data HPIV-1 may account for 5,800 to 28,900 annual hospitalizations; HPIV-2 for 1,800 to 15,600 hospitalizations; and HPIV-3 for 8,700 to 52,000 hospitalizations. CONCLUSIONS: We provide broad, serotype-specific estimates of US childhood hospitalizations associated with HPIV infections. More precise estimates of HPIV-associated hospitalizations would require large prospective studies of HPIV-associated diseases by more sensitive viral testing methods, such as polymerase chain reaction techniques.

Bronchiolitis-associated mortality and estimates of respiratory syncytial virus-associated deaths among US children, 1979-1997.

A 1985 estimate that 4500 respiratory syncytial virus (RSV)-associated deaths occur annually among US children has not been updated using nationally representative data. Thus, 1979-1997 multiple cause-of-death records for children <5 years old listing bronchiolitis, pneumonia, or any respiratory tract disease were examined. Deaths among children associated with any respiratory disease declined from 4631 in 1979 to 2502 in 1997. During the 19-year study period, 1806 bronchiolitis-associated deaths occurred (annual mean, 95 deaths; range, 66-127 deaths). Of these deaths, 1435 (79%) occurred among infants <1 year old. Congenital heart disease, lung disease, or prematurity was listed in death records of 179 (9.9%), 99 (5.5%), and 76 (4.2%) children dying with bronchiolitis, respectively. By applying published proportions of children hospitalized for bronchiolitis or pneumonia who were RSV-infected to bronchiolitis and pneumonia deaths, it was estimated that < or =510 RSV-associated deaths occurred annually during the study period, fewer than previously estimated.

Asthma and bronchiolitis hospitalizations among American Indian children.

OBJECTIVE: To compare asthma and bronchiolitis hospitalization rates in American Indian and Alaskan native (AI/AN) children and all children in Washington State. METHODS: A retrospective data analysis using Washington State hospitalization data for 1987 through 1996. Patients were included if asthma or bronchiolitis was the first-listed diagnosis. American Indian and Alaskan native children were identified by linking state hospitalization data with Indian Health Service enrollment data. RESULTS: Similar rates of asthma hospitalization were found for AI/AN children older than 1 year compared with all children. In AI/AN children younger than 1 year, hospitalization rates for asthma (528 per 100,000 population; 95% confidence interval [CI], 346-761) and bronchiolitis (2954 per 100,000 population; 95% CI, 2501-3456) were 2 to 3 times higher than the rates in all children (232 per 100,000 population [95% CI, 215-251] and 1190 per 100,000 population [95% CI, 1149-1232], respectively). Hospitalization rates for asthma and bronchiolitis increased 50% between 1987 and 1996 for all children younger than 1 year and almost doubled for AI/AN children younger than 1 year. CONCLUSIONS: American Indian and Alaskan native children have significantly higher rates of hospitalization for wheezing illnesses during the first year of life compared with children of other age groups and races. Furthermore, the disparities in rates have increased significantly over time. Future public health measures directed at managing asthma and bronchiolitis should target AI/AN infants.

Risk factors for Nipah virus infection among abattoir workers in Singapore.

During 10-19 March 1999, 11 workers in 1 of 2 Singaporean abattoirs developed Nipah-virus associated encephalitis or pneumonia, resulting in 1 fatality. A case-control study was conducted to determine occupational risk factors for infection. Case patients were abattoir A workers who had anti-Nipah IgM antibodies; control subjects were randomly selected abattoir A workers who tested negative for anti-Nipah IgM. All 13 case patients versus 26 (63%) of 41 control subjects reported contact with live pigs (P=.01). Swine importation from Malaysian states concurrently experiencing a Nipah virus outbreak was banned on 3 March 1999; on 19 March 1999, importation of Malaysian pigs was banned, and abattoirs were closed. No unusual illnesses among pigs processed during February-March were reported. Contact with live pigs appeared to be the most important risk factor for human Nipah virus infection. Direct contact with live, potentially infected pigs should be minimized to prevent transmission of this potentially fatal zoonosis to humans.

Mortality from pneumonia in children in the United States, 1939 through 1996.

BACKGROUND AND METHODS: Pneumonia remains an important cause of childhood deaths throughout the world, but in developed countries, the mortality rate is decreasing. We reviewed death records for children in the United States from 1939 through 1996. A plot of the annual rates of change in the number of deaths from pneumonia was used to generate hypotheses about the influence of various events and interventions. We used data from the National Hospital Discharge Survey, the Medicaid program, and published reports to test these hypotheses. RESULTS: During the 58-year study period, the number of children who died from pneumonia declined by 97 percent, from 24,637 in 1939 to 800 in 1996. During the same period, the rate of mortality from other causes declined by 82 percent. There were steep declines in the mortality rates for pneumonia from 1944 to 1950, although the rate increased among older children in 1957, and there were sustained declines in all age groups from 1966 to 1982. From 1966 to 1982, the mortality declined by an average of 13.0 percent annually, and these decreases coincided with increases in the proportion of poor children covered by Medicaid, increases in rates of hospitalization for pneumonia, a narrowing of the gap between the mortality rate for black children and the rate for white children, and a convergence between the mortality rate in the South and the rates in the other three census regions. CONCLUSIONS: Since 1939, the rate of mortality from pneumonia in children in the United States has declined markedly. We hypothesize that the steep declines in the late 1940s are attributable to the use of penicillin, that the peak in 1957 was due to the influenza A pandemic, and that the sustained decline from 1966 through 1982 may be attributable in part to improved access to medical care for poor children.

An outbreak of cryptosporidiosis linked to a foodhandler.

In September and October 1998, a cryptosporidiosis outbreak occurred on a Washington, DC, university campus. In a case-control study of 88 case patients and 67 control subjects, eating in 1 of 2 cafeterias was associated with diarrheal illness (P<.001). Morbidity was associated with eating dinner on 22 September (odds ratio, 8.1; 95% confidence interval, 3.4-19.5); weaker associations were found for 6 other meals. Cryptosporidium parvum was detected in stool specimens of 16 (70%) of 23 ill students and 2 of 4 ill employees. One ill foodhandler with laboratory-confirmed C. parvum prepared raw produce on 20-22 September. All 25 Cryptosporidium isolates submitted for DNA analysis, including 3 from the ill foodhandler, were genotype 1. This outbreak illustrates the potential for cryptosporidiosis to cause foodborne illness. Epidemiologic and molecular evidence indicate that an ill foodhandler was the likely outbreak source.

Influenza and the rates of hospitalization for respiratory disease among infants and young children.

BACKGROUND: Young children may be at increased risk for serious complications from influenzavirus infection. However, in population-based studies it has been difficult to separate the effects of influenzavirus from those of respiratory syncytial virus. Respiratory syncytial virus often circulates with influenzaviruses and is the most frequent cause of hospitalization for lower respiratory tract infections in infants and young children. We studied the rates of hospitalization for acute respiratory-disease among infants and children during periods when the circulation of influenzaviruses predominated over the circulation of respiratory syncytial virus. METHODS: For each season from October to May during the period from 1992 to 1997, we used local viral surveillance data to define periods in Washington State and northern California when the circulation of influenzaviruses predominated over that of respiratory syncytial virus. We calculated the rates of hospitalization for acute respiratory disease, excess rates attributable to influenzavirus, and incidence-rate ratios for all infants and children younger than 18 years of age who were enrolled in either the Kaiser Permanente Medical Care Program of Northern California or the Group Health Cooperative of Puget Sound. RESULTS: The rates of hospitalization for acute respiratory disease among children who did not have conditions that put them at high risk for complications of influenza (e.g., asthma, cardiovascular diseases, or premature birth) and who were younger than two years of age were 231 per 100,000 person-months at Northern California Kaiser sites (from 1993 to 1997) and 193 per 100,000 person-months at Group Health Cooperative sites (from 1992 to 1997). These rates were approximately 12 times as high as the rates among children without high-risk conditions who were 5 to 17 years of age (19 per 100,000 person-months at Northern California Kaiser sites and 16 per 100,000 person-months at Group Health Cooperative sites) and approached the rates among children with chronic health conditions who were 5 to 17 years of age (386 per 100,000 person-months and 216 per 100,000 person-months, respectively). CONCLUSIONS: Infants and young children without chronic or serious medical conditions are at increased risk for hospitalization during influenza seasons. Routine influenza vaccination should be considered in these children.

Bronchiolitis-associated hospitalizations among American Indian and Alaska Native children.

BACKGROUND: Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract illness among infants and young children. Respiratory system diseases account for a large proportion of hospitalizations in American Indian and Alaska Native (AI/AN) children; however, aggregate estimates of RSV-associated hospitalizations among AI/AN children have not been made. METHODS: We used Indian Health Service hospitalization data from 1990 through 1995 to describe hospitalizations associated with bronchiolitis, the most characteristic clinical manifestation of RSV infection, among AI/AN children <5 years old. RESULTS: The overall bronchiolitis-associated hospitalization rate among AI/AN infants < 1 year old was considerably higher (61.8 per 1,000) than the 1995 estimated bronchiolitis hospitalization rate among all US infants (34.2 per 1,000). Hospitalization rates were higher among male infants (72.2 per 1,000) than among females infants (51.1 per 1,000). The highest infant hospitalization rate was noted in the Navajo Area (96.3 per 1,000). Hospitalizations peaked annually in January or February, consistent with national peaks for RSV detection. Bronchiolitis hospitalizations accounted for an increasing proportion of hospitalizations for lower respiratory tract illnesses. CONCLUSIONS: Bronchiolitis-associated hospitalization rates are substantially greater for AI/AN infants than those for all US infants. This difference may reflect an increased likelihood of severe RSV-associated disease or a decreased threshold for hospitalization among AI/AN infants with bronchiolitis compared with all US infants. AI/AN children would receive considerable benefit from lower respiratory tract illness prevention programs, including an RSV vaccine, if and when one becomes available.

Bronchiolitis-associated hospitalizations among US children, 1980-1996.

CONTEXT: Respiratory syncytial virus (RSV) causes more lower respiratory tract infections, often manifested as bronchiolitis, among young children than any other pathogen. Few national estimates exist of the hospitalizations attributable to RSV, and recent advances in prophylaxis warrant an update of these estimates. OBJECTIVES: To describe rates of bronchiolitis-associated hospitalizations and to estimate current hospitalizations associated with RSV infection. DESIGN AND SETTING: Descriptive analysis of US National Hospital Discharge Survey data from 1980 through 1996. PARTICIPANTS: Children younger than 5 years who were hospitalized in short-stay, non-federal hospitals for bronchiolitis. MAIN OUTCOME MEASURE: Bronchiolitis-associated hospitalization rates by age and year. RESULTS: During the 17-year study period, an estimated 1.65 million hospitalizations for bronchiolitis occurred among children younger than 5 years, accounting for 7.0 million inpatient days. Fifty-seven percent of these hospitalizations occurred among children younger than 6 months and 81 % among those younger than 1 year. Among children younger than 1 year, annual bronchiolitis hospitalization rates increased 2.4-fold, from 12.9 per 1000 in 1980 to 31.2 per 1000 in 1996. During 1988-1996, infant hospitalization rates for bronchiolitis increased significantly (P for trend <.001), while hospitalization rates for lower respiratory tract diseases excluding bronchiolitis did not vary significantly (P for trend = .20). The proportion of hospitalizations for lower respiratory tract illnesses among children younger than 1 year associated with bronchiolitis increased from 22.2% in 1980 to 47.4% in 1996; among total hospitalizations, this proportion increased from 5.4% to 16.4%. Averaging bronchiolitis hospitalizations during 1994-1996 and assuming that RSV was the etiologic agent in 50% to 80% of November through April hospitalizations, an estimated 51, 240 to 81, 985 annual bronchiolitis hospitalizations among children younger than 1 year were related to RSV infection. CONCLUSIONS: During 1980-1996, rates of hospitalization of infants with bronchiolitis increased substantially, as did the proportion of total and lower respiratory tract hospitalizations associated with bronchiolitis. Annual bronchiolitis hospitalizations associated with RSV infection among infants may be greater than previous estimates for RSV bronchiolitis and pneumonia hospitalizations combined.

Development and estimation of a pediatric chronic disease score using automated pharmacy data.

BACKGROUND: Although risk assessment models for specific adult populations such as the elderly have been developed, little work has focused on developing pediatric-specific models. The lack of pediatric models may result in incorrect estimates of relative disease severity among children, in reduced reimbursement for health plans and providers, and in inadequate health care for chronically ill children. OBJECTIVES: To develop and to evaluate a pediatric risk assessment model using automated pharmacy data. DESIGN: Retrospective, case-cohort study using automated data. SUBJECTS: All children continuously enrolled in Group Health Cooperative of Puget Sound during 1992 and 1993. MEASURES: The Pediatric Chronic Disease Score (PCDS), an algorithm that classified children into chronic disease categories by prescription drug fills, was compared with the ICD-9-CM-based Ambulatory Care Groups (ACG) model and a demographic model for prediction of total, ambulatory, or primary care costs and primary care visits. Forecast models were estimated using linear regression and they were evaluated with R2, mean prediction error, mean squared prediction error, and Mincer-Zarnowitz tests. RESULTS: The pharmacy-based PCDS performed significantly better on each of the four forecasting accuracy tests than did a demographic model (eg, R2s averaging fourfold higher). Compared with the ACG model, the PCDS model performed similarly on mean squared prediction error tests; however, the ACG generally had higher validation R2 values. CONCLUSIONS: A pharmacy-based pediatric risk assessment model performs better than a demographic model and represents a viable alternative to ICD-9-CM-based models. Further research is necessary to determine if children must be considered separately from adults when conducting population-based risk assessments.

Infection-control measures reduce transmission of vancomycin-resistant enterococci in an endemic setting.

BACKGROUND: Vancomycin-resistant enterococci (VRE) are nosocomial pathogens in many U. S. hospitals. OBJECTIVE: To determine whether enhanced infection-control strategies reduce transmission of VRE in an endemic setting. DESIGN: Prospective cohort study. SETTING: Adult oncology inpatient unit. PATIENTS: 259 patients evaluated during use of enhanced infection-control strategies and 184 patients evaluated during use of standard infection-control practices. INTERVENTIONS: Patient surveillance cultures were taken, patients were assigned to geographic cohorts, nurses were assigned to patient cohorts, gowns and gloves were worn on room entry, compliance with infection-control procedures was monitored, patients were educated about VRE transmission, patients taking antimicrobial agents were evaluated by an infectious disease specialist, and environmental surveillance was performed. MEASUREMENTS: VRE infection rates, VRE colonization rates, and changes in antimicrobial use. RESULTS: During use of enhanced infection-control strategies, incidence of VRE bloodstream infections decreased significantly (0.45 patients per 1000 patient-days compared with 2.1 patients per 1000 patient-days; relative rate ratio, 0.22 [95% CI, 0.05 to 0.92]; P = 0.04), as did VRE colonization (10.3 patients per 1000 patient-days compared with 20.7 patients per 1000 patient-days; relative rate ratio, 0.5 [CI, 0.33 to 0.75]; P < 0.001). Use of all antimicrobial agents except clindamycin and amikacin was significantly reduced. CONCLUSION: Enhanced infection-control strategies reduced VRE transmission in an oncology unit in which VRE were endemic.

An outbreak of acute gastroenteritis in a geriatric long-term-care facility: combined application of epidemiological and molecular diagnostic methods.

OBJECTIVE: To assess possible transmission modes of, and risk factors for, gastroenteritis associated with Norwalk-like viruses (NLVs) in a geriatric long-term-care facility. METHODS: During a prolonged outbreak of acute gastroenteritis, epidemiological data on illness among residents and employees were collected in conjunction with stool, vomitus, and environmental specimens for viral testing. NLVs were identified by electron microscopy in stool and vomitus specimens, and further characterized by reverse-transcriptase polymerase chain reaction and nucleotide sequencing. Potential risk factors were examined through medical-record review, personal interview, and a self-administered questionnaire sent to all employees. RESULTS: During the outbreak period, 52 (57%) of 91 residents and 34 (35%) of 90 employees developed acute gastroenteritis. Four case-residents were hospitalized; three residents died at the facility shortly after onset of illness. A point source was not identified; no association between food or water consumption and gastroenteritis was identified. A single NLV strain genetically related to Toronto virus was the only pathogen identified. Residents were at significantly higher risk of gastroenteritis if they were physically debilitated (relative risk [RR], 3.5; 95% confidence interval [CI95], 1.0-12.9), as were employees exposed to residents with acute gastroenteritis (RR, 2.6; CI95, 1.1-6.5) or ill household members (RR, 2.3; CI95, 1.4-3.6). Adherence to infection control measures among the nursing staff may have reduced the risk of gastroenteritis, but the reduction did not reach statistical significance. CONCLUSIONS: In the absence of evidence for food-borne or waterborne transmission, NLVs likely spread among residents and employees of a long-term-care facility through person-to-person or airborne droplet transmission. Rapid notification of local health officials, collection of clinical specimens, and institution of infection control measures are necessary if viral gastroenteritis transmission is to be limited in institutional settings.

Perinatal risk factors for infant hospitalization with viral gastroenteritis.

CONTEXT: A tetravalent vaccine against rotavirus, the most commonly identified etiologic agent of viral gastroenteritis (GE), has recently been licensed for use in the United States. OBJECTIVE: To evaluate whether specific groups of infants might be at sufficiently high risk to warrant a focused rotavirus vaccine policy, we investigated perinatal risk factors for hospitalization with viral GE and rotavirus in the first year of life. DESIGN: Population-based, case-control study. SETTING: Washington State linked birth certificate and hospital discharge abstracts from 1987 through 1995. PATIENTS: Infants, 1 through 11 months of age, hospitalized for viral GE (N = 1606) were patients in this study. Control subjects were 8084 nonhospitalized infants, frequency-matched to patients on year of birth. PRIMARY OUTCOME MEASURE: Maternal and infant characteristics associated with infant hospitalization for viral GE. RESULTS: We found a significant association between birth weight and the risk for hospitalization. Very low birth weight infants (<1500 g) were at the highest risk (odds ratio [OR] 2.6; 95% confidence interval [CI]: 1.6,4.1);, low birth weight infants (1500-2499 g), at intermediate risk (OR 1.6; 95% CI: 1.3,2.1); and large infants (>4000 g), at reduced risk (OR 0.8; 95% CI: 0.6,0.9). Other characteristics associated with GE hospitalization were male gender (OR 1.4; 95% CI: 1.3,1.6); maternal smoking (OR 1.2; 95% CI: 1.1,1. 4); unmarried mother (OR 1.2; 95% CI: 1.1,1.4); Medicaid insurance (OR 1.4; 95% CI: 1.3,1.7); and maternal age <20 years (OR 1.2; 95% CI: 1.0,1.5). Infants born October through December were at decreased risk for hospitalization (OR 0.8; 95% CI: 0.7,0.9), as were infants born to Asian mothers (OR 0.5; 95% CI: 0.3,0.7), and infants born to mothers >34 years of age (OR 0.7; 95% CI: 0.6,0.9). Using these factors, the area under a receiver operating characteristic curve was 0.63. Therefore, to achieve a sensitivity of 90% in identifying high-risk infants, specificity would fall to 10%. Subanalyses of children admitted for viral GE during the peak of the Northwest rotavirus season (January to March) and children with confirmed rotavirus infection demonstrated similar risk factors and receiver operating characteristic curves. CONCLUSION: We conclude that a focused rotavirus vaccination policy using readily identifiable potential high-risk groups would be unlikely to prevent most infant hospitalizations associated with rotavirus infection. However, the safety of rotavirus vaccine in low birth weight and premature infants must be established, because these children appear to be at greater risk for hospitalization with viral GE and rotavirus.