Infectious Disease Hospitalizations Among American Indian/Alaska Native and Non-American Indian/Alaska Native Persons in Alaska, 2010-2011.

OBJECTIVE: Reports about infectious disease (ID) hospitalization rates among American Indian/Alaska Native (AI/AN) persons have been constrained by data limited to the tribal health care system and by comparisons with the general US population. We used a merged state database to determine ID hospitalization rates in Alaska. METHODS: We combined 2010 and 2011 hospital discharge data from the Indian Health Service and the Alaska State Inpatient Database. We used the merged data set to calculate average annual age-adjusted and age-specific ID hospitalization rates for AI/AN and non-AI/AN persons in Alaska. We stratified the ID hospitalization rates by sex, age, and ID diagnosis. RESULTS: ID diagnoses accounted for 19% (6501 of 34 160) of AI/AN hospitalizations, compared with 12% (7397 of 62 059) of non-AI/AN hospitalizations. The average annual age-adjusted hospitalization rate was >3 times higher for AI/AN persons (2697 per 100 000 population) than for non-AI/AN persons (730 per 100 000 population; rate ratio = 3.7, P < .001). Lower respiratory tract infection (LRTI), which occurred in 38% (2486 of 6501) of AI/AN persons, was the most common reason for ID hospitalization. AI/AN persons were significantly more likely than non-AI/AN persons to be hospitalized for LRTI (rate ratio = 5.2, P < .001). CONCLUSIONS: A substantial disparity in ID hospitalization rates exists between AI/AN and non-AI/AN persons, and the most common reason for ID hospitalization among AI/AN persons was LRTI. Public health programs and policies that address the risk factors for LRTI are likely to benefit AI/AN persons.

Potentially preventable hospitalizations for acute and chronic conditions in Alaska, 2010-2012.

OBJECTIVE: The U.S. Agency for Healthcare Research and Quality's Prevention Quality Indicators comprise acute and chronic conditions for which hospitalization can be potentially prevented by high-quality ambulatory care. The Healthy Alaska 2020 initiative (HA2020) targeted reducing potentially preventable hospitalizations (PPH) for acute and chronic conditions among its health indicators. We estimated the PPH rate for adults aged ≥ 18 years in Alaska during 2010-2012. METHODS: We conducted a cross-sectional analysis of state-wide hospital discharge data obtained from the Healthcare Cost and Utilization Project and the Indian Health Service. We calculated average annual PPH rates/1000 persons for acute/chronic conditions. Age-adjusted rate ratios (aRRs) were used for evaluating PPH rate disparities between Alaska Native (AN) and non-AN adults. RESULTS: Among 127,371 total hospitalizations, 4911 and 6721 were for acute and chronic PPH conditions, respectively. The overall crude PPH rate was 7.3 (3.1 for acute and 4.2 for chronic conditions). AN adults had a higher rate than non-AN adults for acute (aRR: 4.7; p < 0.001) and chronic (aRR: 2.6; p < 0.001) PPH conditions. Adults aged ≥ 85 years had the highest PPH rate for acute (43.5) and chronic (31.6) conditions. Acute conditions with the highest PPH rate were bacterial pneumonia (1.8) and urinary tract infections (0.8). Chronic conditions with the highest PPH rate were chronic obstructive pulmonary disease (COPD; 1.6) and congestive heart failure (CHF; 1.3). CONCLUSION: Efforts to reduce PPHs caused by COPD, CHF, and bacterial pneumonia, especially among AN people and older adults, should yield the greatest benefit in achieving the HA2020 goal.

Infant and maternal risk factors related to necrotising enterocolitis-associated infant death in the United States.

AIM: To evaluate necrotising enterocolitis (NEC)-associated infant death and identify risk factors related to NEC infant death in the United States. METHODS: The United States Period Linked Birth/Infant Death data for 2010-2013 were utilised to determine risk factors associated with NEC infant death. Infant mortality rates (IMRs) were calculated and a retrospective matched case-control analysis was performed. An infant case was defined as having the International Classification of Diseases, Tenth Revision code for NEC listed on the death record. Controls were matched on birthweight and randomly selected. Conditional multivariable logistic regression models stratified by birthweight were conducted to determine risk factors for NEC infant death. RESULTS: The average annual NEC IMR was 12.5 deaths per 100 000 live births and was higher among very low birthweight (VLBW) compared to normal birthweight infants and among black compared to white infants. For VLBW infants, the multivariable analysis identified male sex, five-minute Apgar score of less than 7, and white infants born to a mother who is less than or equal to 19 years of age to be related with NEC-associated infant death. CONCLUSION: Paediatricians should be aware of the factors related to NEC-associated infant death to reduce the number of infants at greatest risk for NEC and focus on racial disparities.

Chronic Liver Disease-Associated Hospitalizations Among Adults with Diabetes, National Inpatient Sample, 2001-2012.

OBJECTIVE: Many people with diabetes have a variety of diabetes-related complications. Among the variety of conditions associated with diabetes, however, liver diseases are less well recognized. As such, we aimed to describe chronic liver disease (CLD)-associated hospitalization rates among U.S. adults with diabetes from 2001-2012. METHODS: We used a nationally representative database of hospitalizations, the National Inpatient Sample, to determine CLD-associated hospitalization rates among U.S. adults aged ≥ 18 years with and without diabetes, from 2001-2012. Hospitalizations listing an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code for CLD on the discharge record were selected for analysis and were further classified by diabetes status based on concurrent presence of a diabetes ICD-9-CM code. We calculated average annual age-adjusted hospitalization rates and 95% confidence intervals (CIs), and conducted a test for trend. RESULTS: For 2001-2012, the total age-adjusted CLD-associated hospitalization rate among adults with diabetes (1,680.9 per 100,000 population; 95% CI 1,577.2, 1,784.6) was approximately four times the rate of adults without diabetes (424.2 per 100,000 population; 95% CI 413.4, 435.1). Total age-adjusted hospitalization rates of adults with and without diabetes increased 59% and 48%, respectively, from 2001-2002 to 2011-2012 (p<0.001). Hepatitis C- and chronic hepatitis and cirrhosis-associated hospitalizations comprised the largest proportion of total CLD-associated hospitalizations among adults with and without diabetes. CONCLUSION: Providers should be aware of the potential existence of CLD among adults with diabetes and counsel patients on preventive methods to avoid progressive liver damage.

Lower respiratory tract infection hospitalizations among American Indian/Alaska Native children and the general United States child population.

BACKGROUND: The lower respiratory tract infection (LRTI)-associated hospitalization rate in American Indian and Alaska Native (AI/AN) children aged <5 years declined during 1998-2008, yet remained 1.6 times higher than the general US child population in 2006-2008. PURPOSE: Describe the change in LRTI-associated hospitalization rates for AI/AN children and for the general US child population aged <5 years. METHODS: A retrospective analysis of hospitalizations with discharge ICD-9-CM codes for LRTI for AI/AN children and for the general US child population <5 years during 2009-2011 was conducted using Indian Health Service direct and contract care inpatient data and the Nationwide Inpatient Sample, respectively. We calculated hospitalization rates and made comparisons to previously published 1998-1999 rates prior to pneumococcal conjugate vaccine introduction. RESULTS: The average annual LRTI-associated hospitalization rate declined from 1998-1999 to 2009-2011 in AI/AN (35%, p<0.01) and the general US child population (19%, SE: 4.5%, p<0.01). The 2009-2011 AI/AN child average annual LRTI-associated hospitalization rate was 20.7 per 1,000, 1.5 times higher than the US child rate (13.7 95% CI: 12.6-14.8). The Alaska (38.9) and Southwest regions (27.3) had the highest rates. The disparity was greatest for infant (<1 year) pneumonia-associated and 2009-2010 H1N1 influenza-associated hospitalizations. CONCLUSIONS: Although the LRTI-associated hospitalization rate declined, the 2009-2011 AI/AN child rate remained higher than the US child rate, especially in the Alaska and Southwest regions. The residual disparity is likely multi-factorial and partly related to household crowding, indoor smoke exposure, lack of piped water and poverty. Implementation of interventions proven to reduce LRTI is needed among AI/AN children.

Recurrent Kawasaki disease: USA and Japan.

BACKGROUND: Descriptive epidemiologic studies of recurrent and non-recurrent Kawasaki disease (KD) may identify other potentially important differences between these illnesses. METHODS: Data from the USA and Japan, the Centers for Disease Control and Prevention (CDC) national KD surveillance(1984-2008) and the 17th Japanese nationwide survey (2001-2002), respectively, were analyzed to examine recurrent KD patients <18 years of age meeting the CDC KD case or atypical KD case definition. These patients were compared with non-recurrent KD patients. RESULTS: Of the 5557 US KD patients <18 years of age during 1984-2008, 97 (1.7%) were identified as having had recurrent KD. Among the US Asian/Pacific Islander KD patients, 3.5% had recurrent KD, which was similar to the percentage identified among KD patients (3.5%) in the Japanese survey. Compared with non-recurrent KD patients, KD patients [with recurrent KD] were more likely to be older, fulfill the atypical KD case definition, and have coronary artery abnormalities (CAA) despite i.v. immunoglobulin (IVIG) treatment. CONCLUSIONS: Differences in the age, race, and frequency of CAA exist between recurrent and non-recurrent KD patients. The increased association of CAA with recurrent KD suggests that more aggressive treatment strategies in conjunction with IVIG may be indicated for the second episode of KD.

Rickets and vitamin D deficiency in Alaska native children.

BACKGROUND: Rickets and vitamin D deficiency appeared to increase in Alaskan children starting in the 1990s. We evaluated the epidemiology of rickets and vitamin D deficiency in Alaska native (AN) children in 2001-2010. METHODS: We analyzed 2001-2010 visits with rickets or vitamin D deficiency diagnosis for AN and American Indian children and the general US population aged <10 years. We conducted a case-control study of AN rickets/vitamin D deficient cases and age- and region-matched controls. RESULTS: In AN children, annual rickets-associated hospitalization rate (2.23/100,000 children/year) was higher than the general US rate (1.23; 95% CI 1.08-1.39). Rickets incidence increased with latitude. Rickets/vitamin D deficiency cases were more likely to have malnutrition (OR 38.1; 95% CI 4.9-294), had similar breast-feeding prevalence, and were less likely to have received vitamin D supplementation (OR 0.23; 95% CI 0.1-0.87) than controls. CONCLUSIONS: Our findings highlight the importance of latitude, malnutrition, and lack of vitamin D supplementation as risk factors for rickets.

Incidence and prevalence of Parkinson's disease among Navajo people living in the Navajo nation.

Parkinson's disease (PD) is largely unstudied among American Indians. Unique populations might harbor clues to elusive causes. We describe the incidence and prevalence of PD among Navajo people residing in the Navajo Nation, home to the largest American Indian tribe in the United States. We analyzed 2001-2011 inpatient and outpatient visit data for Navajo people obtained from the Indian Health Service, which provides health care to American Indian people living on the Navajo Reservation. Cases were defined by at least two inpatient or outpatient visits with the diagnosis of PD. Crude and age-adjusted incidence and prevalence rates were calculated overall as well as by age, sex, region of residence, and time period. Five hundred twenty-four Navajo people with median age-at-onset of 74.0 years were diagnosed with PD during the study period, yielding an average annual crude incidence rate of 22.5/100,000. Age-specific incidence was 232.0 for patients 65 years of age or older and 302.0 for 80 years of age or older. Age-adjusted incidence was 35.9 overall (238.1 for ≥65 years), was higher in men than in women (47.5 vs. 27.7; P<0.001), varied by region (P=0.03), and was similar between time periods (2002-2004 vs. 2009-2011). The age-adjusted point prevalence rate was 261.0. The rate of PD among Navajo People appears to be as high as or higher than rates reported in many other populations. Rates increased to the highest age group, consistent with population-based studies. Further investigation is warranted to examine risk factors for PD in this remote population.

Leptospirosis-associated hospitalizations, United States, 1998-2009.

A small percentage of persons with leptospirosis, a reemerging zoonosis, experience severe complications that require hospitalization. The number of leptospirosis cases in the United States is unknown. Thus, to estimate the hospitalization rate for this disease, we analyzed US hospital discharge records for 1998-2009 for the total US population by using the Nationwide Inpatient Sample. During that time, the average annual rate of leptospirosis-associated hospitalizations was 0.6 hospitalizations/1,000,000 population. Leptospirosis-associated hospitalization rates were higher for persons >20 years of age and for male patients. For leptospirosis-associated hospitalizations, the average age of patients at admission was lower, the average length of stay for patients was longer, and hospital charges were higher than those for nonleptospirosis infectious disease-associated hospitalizations. Educating clinicians on the signs and symptoms of leptospirosis may result in earlier diagnosis and treatment and, thereby, reduced disease severity and hospitalization costs.

Understanding the burden of tuberculosis among American Indians/Alaska Natives in the U.S.: a validation study.

OBJECTIVE: We validated cases of active tuberculosis (TB) recorded in the Indian Health Service (IHS) National Patient Information Reporting System (NPIRS) and evaluated the completeness of TB case reporting from IHS facilities to state health departments. METHODS: We reviewed the medical records of American Indian/Alaska Native (AI/AN) patients at IHS health facilities who were classified as having active TB using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnostic codes from 2006 to 2009 for clinical and laboratory evidence of TB disease. Individuals were reclassified as having active TB disease; recent latent TB infection (LTBI); past positive tuberculin skin test (TST) only; or as having no evidence of TB, LTBI, or a past positive TST. We compared validated active TB cases with corresponding state records to determine if they were reported. RESULTS: The study included 596 patients with active TB as per ICD-9-CM codes. Based on chart review, 111 (18.6%) had active TB; 156 (26.2%) had LTBI; 104 (17.4%) had a past positive TST; and 221 (37.1%) had no evidence of TB disease, LTBI, or a past positive TST. Of the 111 confirmed cases of active TB, 89 (80.2%) resided in participating states; 81 of 89 (91.2%) were verified as reported TB cases. CONCLUSIONS: ICD-9-CM codes for active TB disease in the IHS NPIRS do not accurately reflect the burden of TB among AI/ANs. Most confirmed active TB cases in the IHS health system were reported to the state; the national TB surveillance system may accurately represent the burden of TB in the AI/AN population.

Molluscum contagiosum in a pediatric American Indian population: incidence and risk factors.

BACKGROUND: Molluscum contagiosum virus (MCV) causes an innocuous yet persistent skin infection in immunocompetent individuals and is spread by contact with lesions. Studies point to atopic dermatitis (AD) as a risk factor for MCV infection; however, there are no longitudinal studies that have evaluated this hypothesis. METHODS: Outpatient visit data from fiscal years 2001-2009 for American Indian and Alaska Native (AI/AN) children were examined to describe the incidence of molluscum contagiosum (MC). We conducted a case-control study of patients <5 years old at an Indian Health Service (IHS) clinic to evaluate dermatological risk factors for infection. RESULTS: The incidence rate for MC in children <5 years old was highest in the West and East regions. MC cases were more likely to have a prior or co-occurring diagnosis of eczema, eczema or dermatitis, impetigo, and scabies (p<0.05) compared to controls; 51.4% of MC cases had a prior or co-occurring diagnosis of eczema or dermatitis. CONCLUSIONS: The present study is the first demonstration of an association between AD and MC using a case-control study design. It is unknown if the concurrent high incidence of eczema and MC is related, and this association deserves further investigation.

Trends in encephalitis-associated deaths in the United States, 1999-2008.

BACKGROUND: While encephalitis may be caused by numerous infectious, immune and toxic processes, the etiology often remains unknown. METHODS: We analyzed multiple cause-of-death mortality data during 1999-2008 for the USA, using the 10th revision of International Classification of Diseases codes for encephalitis, listed anywhere on the death record, including 'specified' and 'unspecified' encephalitis. Annual and average annual age-adjusted and age-specific death rates were calculated. RESULTS: For 1999-2008, 12,526 encephalitis-associated deaths were reported with 68.5% as unspecified encephalitis. The average annual age-adjusted encephalitis-associated death rate was 4.3 per 1 million persons, 1.3 for specified and 2.9 for unspecified encephalitis. Annual encephalitis-associated death rates had a significant downward trend (p < 0.01). The most common specified encephalitis deaths were herpesviral encephalitis (36.7%), Toxoplasma meningoencephalitis (27.8%) and Listeria meningitis/meningoencephaltis (6.8%). HIV was colisted with 15.0% of encephalitis-associated deaths, 58.4% of these with a specified code. CONCLUSION: Encephalitis-associated death rates decreased during 1999-2008, and herpesvirus was the most commonly identified infectious agent associated with encephalitis deaths. The high proportion of unspecified encephalitis deaths highlights the continued challenge of laboratory confirmation for causes of encephalitis and the importance of monitoring trends to assess the impact of new diagnostics and guide potential interventions.

Risk factors for infectious disease death among infants in the United States.

BACKGROUND: Infectious diseases (IDs) are an important cause of infant mortality in the United States. This study describes maternal and infant characteristics associated with infant ID deaths in the United States. METHODS: Infant deaths with an ID underlying cause of death occurring in the United States were examined using the 2008-2009 Period Linked Birth/Infant Death public use data files. Average annual ID infant mortality rates for singleton infants were calculated. A retrospective case-control study was conducted to determine infant and maternal risk factors for infant ID death among low (LBW) and normal (NBW) birth weight groups. Controls were defined as infants surviving to the end of their birth year. Risk factors for infant ID deaths were determined through multivariable logistic regression. RESULTS: An estimated 3843 infant ID deaths occurred in the United States during 2008-2009, an overall ID infant mortality rate of 47.5 deaths per 100,000 live births. The mortality rate for LBW and NBW infants were 514.8 and 15.5, respectively. Male sex, younger maternal age (<25 years), a live birth order of fourth or more and low 5-minute Apgar score were associated with increased ID death among LBW and NBW infants. Additionally, black maternal race was associated with increased ID death among LBW infants, and having an unmarried mother was associated with increased ID death among NBW infants. CONCLUSIONS: Awareness of associations with infant ID death should help in development of further strategic measures to reduce infant ID morbidity and mortality.

Respiratory exacerbations in indigenous children from two countries with non-cystic fibrosis chronic suppurative lung disease/bronchiectasis.

BACKGROUND: Acute respiratory exacerbations (AREs) cause morbidity and lung function decline in children with chronic suppurative lung disease (CSLD) and bronchiectasis. In a prospective longitudinal cohort study, we determined the patterns of AREs and factors related to increased risks for AREs in children with CSLD/bronchiectasis. METHODS: Ninety-three indigenous children aged 0.5 to 8 years with CSLD/bronchiectasis in Australia (n = 57) and Alaska (n = 36) during 2004 to 2009 were followed for > 3 years. Standardized parent interviews, physical examinations, and medical record reviews were undertaken at enrollment and every 3 to 6 months thereafter. RESULTS: Ninety-three children experienced 280 AREs (median = 2, range = 0-11 per child) during the 3-year period; 91 (32%) were associated with pneumonia, and 43 (15%) resulted in hospitalization. Of the 93 children, 69 (74%) experienced more than two AREs over the 3-year period, and 28 (30%) had more than one ARE in each study year. The frequency of AREs declined significantly over each year of follow-up. Factors associated with recurrent (two or more) AREs included age < 3 years, ARE-related hospitalization in the first year of life, and pneumonia or hospitalization for ARE in the year preceding enrollment. Factors associated with hospitalizations for AREs in the first year of study included age < 3 years, female caregiver education, and regular use of bronchodilators. CONCLUSIONS: AREs are common in children with CSLD/bronchiectasis, but with clinical care and time AREs occur less frequently. All children with CSLD/bronchiectasis require comprehensive care; however, treatment strategies may differ for these patients based on their changing risks for AREs during each year of care.

Epidemiology of asthma hospitalizations among American Indian and Alaska Native people and the general United States population.

BACKGROUND: Asthma, a common chronic disease among adults and children in the United States, results in nearly one-half million hospitalizations annually. There has been no evaluation of asthma hospitalizations for American Indian and Alaska Native (AI/AN) people since a previous study using data for 1988-2002. In this study, we describe the epidemiology and trends for asthma hospitalizations among AI/AN people and the general US population for 2003-2011. METHODS: Hospital discharge records with a first-listed diagnosis of asthma for 2003-2011 were examined for AI/AN people, using Indian Health Service (IHS) data, and for the general US population, using the Nationwide Inpatient Sample. Average annual crude and age-adjusted hospitalization rates were calculated. RESULTS: The average annual asthma hospitalization rates for AI/AN people and the general US population decreased from 2003-2005 to 2009-2011 (32% and 11% [SE, 3%], respectively). The average annual age-adjusted rate for 2009-2011 was lower for AI/AN people (7.6 per 10,000 population) compared with the general US population (13.2 per 10,000; 95% CI, 12.8-13.6). Age-specific AI/AN rates were highest among infants and children 1 to 4 years of age. IHS regional rates declined in all regions except Alaska. CONCLUSIONS: Asthma hospitalization rates are decreasing for AI/AN people and the general US population despite increasing prevalence rates. AI/AN people experienced a substantially lower age-adjusted asthma hospitalization rate compared with the general US population. Although the rates for AI/AN infants and children 1 to 4 years of age have declined substantially, they remain higher compared with other age groups. Improved disease management and awareness should help to further decrease asthma hospitalizations, particularly among young children.

American Indian and Alaska Native infant and pediatric mortality, United States, 1999-2009.

OBJECTIVES: We described American Indian/Alaska Native (AI/AN) infant and pediatric death rates and leading causes of death. METHODS: We adjusted National Vital Statistics System mortality data for AI/AN racial misclassification by linkage with Indian Health Service (IHS) registration records. We determined average annual death rates and leading causes of death for 1999 to 2009 for AI/AN versus White infants and children. We limited the analysis to IHS Contract Health Service Delivery Area counties. RESULTS: The AI/AN infant death rate was 914 (rate ratio [RR] = 1.61; 95% confidence interval [CI] = 1.55, 1.67). Sudden infant death syndrome, unintentional injuries, and influenza or pneumonia were more common in AI/AN versus White infants. The overall AI/AN pediatric death rates were 69.6 for ages 1 to 4 years (RR = 2.56; 95% CI = 2.38, 2.75), 28.9 for ages 5 to 9 years (RR = 2.12; 95% CI = 1.92, 2.34), 37.3 for ages 10 to 14 years (RR = 2.22; 95% CI = 2.04, 2.40), and 158.4 for ages 15 to 19 years (RR = 2.71; 95% CI = 2.60, 2.82). Unintentional injuries and suicide occurred at higher rates among AI/AN youths versus White youths. CONCLUSIONS: Death rates for AI/AN infants and children were higher than for Whites, with regional disparities. Several leading causes of death in the AI/AN pediatric population are potentially preventable.

Infectious disease mortality among American Indians and Alaska Natives, 1999-2009.

OBJECTIVES: We described death rates and leading causes of death caused by infectious diseases (IDs) in American Indian/Alaska Native (AI/AN) persons. Methods. We analyzed national mortality data, adjusted for AI/AN race by linkage with Indian Health Service registration records, for all US counties and Contract Health Service Delivery Area (CHSDA) counties. The average annual 1999 to 2009 ID death rates per 100,000 persons for AI/AN persons were compared with corresponding rates for Whites. RESULTS: The ID death rate in AI/AN populations was significantly higher than that of Whites. A reported 8429 ID deaths (rate 86.2) in CHSDA counties occurred among AI/AN persons; the rate was significantly higher than the rate in Whites (44.0; rate ratio [RR] = 1.96; 95% confidence interval [CI] = 1.91, 2.00). The rates for the top 10 ID underlying causes of death were significantly higher for AI/AN persons than those for Whites. Lower respiratory tract infection and septicemia were the top-ranked causes. The greatest relative rate disparity was for tuberculosis (RR = 13.51; 95% CI = 11.36, 15.93). CONCLUSIONS: Health equity might be furthered by expansion of interventions to reduce IDs among AI/AN communities.

Encephalitis-associated hospitalizations among American Indians and Alaska Natives.

Encephalitis produces considerable morbidity in the United States, but morbidity rates among American Indian/Alaska Native (AI/AN) people have not been described. Hospitalization records listing an encephalitis diagnosis were analyzed by using Indian Health Service direct/contract inpatient data. For 1998-2010, there were 436 encephalitis-associated hospitalizations among AI/AN people, an average annual age-adjusted hospitalization rate of 3.1/100,000 population. The rate for infants (11.9) was more than double that for any other age group. Death occurred for 4.1% of hospitalizations. Consistent with reports for the general U.S. population, the rate was high among infants and most (53.9%) hospitalizations were of unexplained etiology. The average annual rate during the study period appeared lower than for the general U.S. population, due particularly to lower rates in the elderly. Future community-based surveillance and mortality studies are needed to confirm these findings and examine reasons underlying the low rates of encephalitis in AI/AN people.

Burden of encephalitis-associated hospitalizations in the United States, 1998-2010.

OBJECTIVE: To estimate the burden of encephalitis-associated hospitalizations in the United States for 1998-2010. METHODS: Using the Nationwide Inpatient Sample, a nationally representative database of hospitalizations, estimated numbers and rates of encephalitis-associated hospitalizations for 1998-2010 were calculated. Etiology and outcome of encephalitis-associated hospitalizations were examined, as well as accompanying diagnoses listed along with encephalitis on the discharge records. Total hospital charges (in 2010 US dollars) were assessed. RESULTS: An estimated 263,352 (standard error: 3,017) encephalitis-associated hospitalizations occurred in the United States during 1998-2010, which corresponds to an average of 20,258 (standard error: 232) encephalitis-associated hospitalizations per year. A fatal outcome occurred in 5.8% (95% confidence interval [CI]: 5.6%-6.0%) of all encephalitis-associated hospitalizations and in 10.1% (95% CI: 9.2%-11.2%) and 17.1% (95% CI: 14.6%-20.0%) of encephalitis-associated hospitalizations in which a code for HIV or a tissue or organ transplant was listed, respectively. The proportion of encephalitis-associated hospitalizations in which an etiology for encephalitis was specified was 50.3% (95% CI: 49.6%-51.0%) and that for which the etiology was unspecified was 49.7% (95% CI: 49.0%-50.4%). Total charges for encephalitis-associated hospitalizations in 2010 were an estimated $2.0 billion. CONCLUSIONS: Encephalitis remains a major public health concern in the United States. Among the large number of encephalitis-associated hospitalizations for which an etiology is not reported may be novel infectious and noninfectious forms of encephalitis. Associated conditions such as HIV or transplantation increase the risk of a fatal outcome from an encephalitis-associated hospitalization and should be monitored.