OBJECTIVE. This study describes the burden and epidemiologic features of infectious disease hospitalizations among infants in the United States.
METHODS. Hospitalizations with an infectious disease listed as a primary diagnosis for infants (<1 year of age) in the United States during 2003 were examined by using the Kids' Inpatient Database. National estimates of infectious disease hospitalizations, hospitalization rates, and various hospital parameters were examined.
RESULTS. During 2003, an estimated 286739 infectious disease hospitalizations occurred among infants in the United States and accounted for 42.8% of all infant hospitalizations. The national infectious disease hospitalization rate was 7010.8 hospitalizations per 100000 live births, or ∼1 infectious disease hospitalization for every 14 infants. The median length of stay was 3 days, and stays totaled >1 million hospital days for infants. Infectious disease hospitalization rates were highest among boys and nonwhite infants. The most commonly listed diagnoses among the infant infectious disease hospitalizations included lower respiratory tract infections (59.0%), kidney, urinary tract, and bladder infections (7.6%), upper respiratory tract infections (6.5%), and septicemia (6.5%). The median cost of an infectious disease hospitalization was $2235, with total annual hospital costs of approximately $690 million, among infants in the United States.
CONCLUSIONS. Infectious disease hospitalizations among infants account for substantial health care expenditures and hospital time in the United States, with respiratory disease hospitalizations constituting more than one half of all hospitalizations. Younger infants, boys, and nonwhite infants were at increased risk for infectious disease hospitalization. Measures to reduce racial disparities and the occurrence of respiratory tract infections should substantially decrease the infectious disease burden among infants.
Despite advances in public health, infectious diseases (IDs) continue to cause significant morbidity and death in the United States.1,2 Although life expectancy has increased and overall mortality rates have decreased along with ID mortality rates in the developed world, the “epidemiologic transition” to predominating degenerative and chronic diseases is not complete.3,4 Many IDs are emerging or reemerging and, although the overall all-cause hospitalization rate in the United States decreased by nearly one third from 1980 to 1994, the ID hospitalization rate decreased by less than one half of that amount (12%).2
Rates for ID hospitalizations among infants (<1 year of age) increased by ∼17% in 1988 to 1999.5 Respiratory conditions account for a large proportion of infant ID hospitalizations, constituting more than one half of infant ID hospitalizations among US infants.5 Bronchiolitis is the most common lower respiratory tract infection (LRTI) in infants.6 Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis, and ∼90% of children are infected with RSV within the first 2 years of life7; of those, up to 40% develop an LRTI.8,9 Moreover, infection with RSV does not confer immunity, and reinfections are common.10 Septicemia is also a major contributor to IDs among infants, particularly in the neonatal period. Although rates of infant deaths attributable to septicemia have decreased in the United States in recent years,11 septicemia remains among the leading causes of infant deaths throughout the world.12 Moreover, although septicemia-related mortality rates are decreasing in the United States, there are still a significant number of infants affected, with severe septicemia being estimated to occur in 1.6 to 5.2 infants per 1000 population.13 This study uses a national database of pediatric hospitalizations to describe the burden and epidemiologic features of ID hospitalizations among infants in the United States.
Hospital discharge records were extracted from the 2003 Kids' Inpatient Database (KID).14 The Healthcare Cost and Utilization Project (HCUP) within the Agency for Healthcare Research and Quality produced the KID in collaboration with public and private statewide data organizations.14,15 The KID sampling frame was constructed by using short-term, nonfederal, general and specialty hospitals with pediatric discharges in 36 participating US states. A 10% sample of uncomplicated births and an 80% sample of other hospitalizations for children ≤20 years of age were taken from all hospitals in the sampling frame. To accommodate the sample survey design of the KID, discharge weights were developed by stratifying hospitals with respect to the following characteristics: ownership/control, bed size, teaching status, rural/urban location, US region, and whether the hospital is a freestanding children's hospital.14 By using weights supplied by the HCUP, national estimates for disease-specific pediatric hospital discharges can be obtained from the KID.14,15
Hospitalizations for infants with an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code for an ID listed as the primary diagnosis on the discharge record were studied.16 IDs were defined by using a previously described classification scheme2,17 for ICD-9-CM codes, with inclusion of perinatal period-specific codes. In addition to overall primary ID analyses, selected subgroups were examined.18 The following ID groups were used for subgroup-specific analysis: tuberculosis (codes 010–018 and 137); meningitis (codes 027.0, 036, 320.0–321.3 and 321.8); septicemia (codes 038 and 771.8); HIV/AIDS (codes 042–044 and 279.1); hepatobiliary disease (codes 070, 095.3, 573.1, 573.2, and 576.1); infections specific to the perinatal period (codes 771.3–771.7); mycoses (codes 110–118); infections of the heart (codes 093, 391, 392.0, 393, 394.1, 395.0–395.2, 397.1, 397.9, 398, 421, 422.0, and 424.9); upper respiratory tract infections (codes 032.0–032.3, 034.0, 098.6, 101, 460–465, 473.0–474.0, and 475); LRTIs (codes 022.1, 031.0, 033, 095.1, 466, 480–487, 510, 511.1, 513, 517.1, and 770.0); abdominal and rectal infections (codes 095.2, 098.7, 540–542, 566, 567.0–567.2, and 569.5); kidney, urinary tract, and bladder infections (codes 095.4, 099.4, 590, 595.0, 597, 598.0, and 599.0); cellulitis (codes 680–686); enteric infections (codes 001–009 and 022.2); and viral central nervous system infections (codes 045–049). Hospitalizations with a newborn diagnosis (indicating a birth) were excluded from this study.
We examined first-listed ID hospitalization records according to age group (neonates: <1 month of age; postneonates: 1–11 months of age), gender and race/ethnicity of the patient, outcome (discharged or died during hospitalization), region of hospital location (standard census regions of Northeast, Midwest, South, and West), admission month, hospital size (small: 1–49 beds for rural hospitals, 1–99 beds for urban nonteaching hospitals, and 1–299 beds for urban teaching hospitals; medium: 50–99 beds for rural hospitals, 100–199 beds for urban nonteaching hospitals, and 300–499 beds for urban teaching hospitals; large: ≥100 beds for rural hospitals, ≥200 beds for urban nonteaching hospitals, and ≥500 beds for urban teaching hospitals), median household income for the patient's zip code of residence ($1–$35999, $36000–$44999, $45000–$59999, or $60000 or more), and expected primary payer (Medicare, Medicaid, private insurance including health maintenance organizations, self-pay, no charge, or other). Race/ethnicity was recorded as one variable (non-Hispanic white, non-Hispanic black, Hispanic, Asian/Pacific Islander, American Indian/Alaska Native, or other race); information on race was missing for 25.5% (SE: 1.6%) of infant ID hospitalizations. Gender (0.2%) and race/ethnicity (25.5%) had missing information, and adjustments were not made for missing data. Accompanying diagnoses and procedures listed with IDs on the hospitalization records were also examined, as were length of stay and total hospital charges. National estimates of the number of hospitalizations, hospital length of stay, and hospital charges were calculated by using HCUP weighting methods.14,15 The estimates were calculated according to age group by using the complete KID maintained at the Agency for Healthcare Research and Quality. To assess the prevalence of secondary ID-associated diagnoses among infant hospitalizations without a primary ID diagnosis, we examined the most frequently listed diagnoses among these records as well. Hospitalization costs were estimated by using cost/charge ratio files provided by HCUP.19 These files use all-payer inpatient cost and charge information from the Center for Medicare and Medicaid Services to estimate the cost/charge ratio for most hospitals in the KID.20 When hospital-specific information was not available, the weighted group average was used to estimate costs. If neither group-specific nor hospital-specific information was available, then the hospital was excluded and the remaining records were reweighted to account for missing cost estimates.14 Hospitalization estimates were not presented if the relative SE (SE/number of estimated hospitalizations) exceeded 0.30, because such estimates are considered unreliable. Estimates of hospitalizations, lengths of stay, and charges were not adjusted for missing data. Because no unique personal identifiers were provided with hospitalization records, the unit of analysis in this study was a hospitalization.
ID hospitalization rates were calculated by using the weighted number of hospitalizations and the number of live births determined from 2003 US natality data.21 Rates are given for both neonates and postneonates and are expressed as the number of hospitalizations per 100000 live births. Population estimates obtained from vital records data were considered free from sampling error. SEs of estimates were calculated by using SUDAAN software (Research Triangle Institute, Research Triangle Park, NC) to account for the sampling design of the KID22 and were used to calculate 95% confidence intervals (CIs) for hospitalization rates; χ2 tests and t tests were used to test for significant differences in categorical and continuous variables, respectively.23
Hospitalization Occurrence, Rates, and Characteristics
During 2003, an estimated 286739 (SE: 8190) hospitalizations with IDs as the primary diagnosis occurred among infants in the United States (Table 1), accounting for 42.8 ± 0.5% of all infant hospitalizations. The ID hospitalization rate was 7010.8 hospitalizations per 100000 live births (95% CI: 6618.3–7403.3 hospitalizations per 100000 live births). Neonates represented 15.4 ± 0.2% (n = 44219 ± 1752) of all infant ID hospitalizations; the neonate ID hospitalization rate was 1081.2 hospitalizations per 100000 live births (95% CI: 997.3–1165.1 hospitalizations per 100000 live births) (Fig 1 and Table 1). The rate for postneonates was 5802.7 hospitalizations per 100000 live births (95% CI: 5471.2–6134.2 hospitalizations per 100000 live births). The largest proportion of ID hospitalizations was among infants in the second month of life; this age group represented 18.9% of hospitalizations. The proportion of ID hospitalizations decreased with increasing age after the second month of life (Fig 1).
The ID hospitalization rate for boys was significantly higher than that for girls (7815.3 and 6138.1 hospitalizations per 100000 live births, respectively) (Table 1). Among the racial groups, non-Hispanic black and Hispanic infants had higher ID hospitalization rates than did non-Hispanic white infants, whereas Asian/Pacific Islander infants had the lowest hospitalization rates. Hospitalization rates were not significantly different between regions, although the South had the highest rate (7879.5.8 hospitalizations per 100000 live births; 95% CI: 6958.4–8800.6 hospitalizations per 100000 live births). There was a clear seasonality of ID hospitalizations, with a prominent peak occurring in the winter months of December through March (Fig 2). The percentages of ID hospitalizations according to month of admission ranged from 4.4 ± 0.1% in July to 14.2 ± 0.2% in January.
More than one half of the ID hospitalizations (54.6 ± 1.5%) were reported from large hospitals (Table 2). Approximately 35.8 ± 1.0% of ID hospitalizations were among infants from households located in areas where the average annual income for the patient's zip code was less than $36000; 15.4 ± 0.7% were from areas with an annual income of at least $60000. Medicaid or private insurance/health maintenance organization was listed as the primary payer for most ID hospitalizations (58.5 ± 0.8% and 35.7 ± 0.8%, respectively).
An estimated 470 ± 39.7 infants died while hospitalized with an ID during 2003; of these, 140 ± 20.0 were neonates. These deaths represented an overall in-hospital fatality rate of 0.16 ± 0.01%. Although the fatality rate in both age groups was low, the fatality rate among neonates was 4 times that among older infants (0.45 ± 0.1% and 0.11 ± 0.01%, respectively). The most common ID diagnosis among fatal neonatal cases was septicemia of the newborn (ICD-9-CM code 771.81; 71.0 ± 5.5%), followed by respiratory failure of the newborn (ICD-9-CM code 770.84; 35.3 ± 6.9%), other shock (ICD-9-CM code 785.59; 29.1 ± 5.5%), and disseminated intravascular coagulation in the newborn (ICD-9-CM code 776.2; 27.9 ± 5.2%). The most common ID diagnoses among fatal postneonatal cases were acute respiratory failure (ICD-9-CM code 518.81; 54.9 ± 4.9%), other shock (ICD-9-CM code 785.59; 30.3 ± 4.5%), and acidosis (ICD-9-CM code 276.2; 29.7 ± 4.3%).
Specific Disease Groups
The most frequently listed ID group for US infants in 2003 was LRTIs, which accounted for 59.0 ± 0.5% of the infant ID hospitalizations (Fig 3 and Table 3). The hospitalization rate for first-listed LRTI was 4135.1 hospitalizations per 100000 live births (95% CI: 3918.7–4351.5 hospitalizations per 100000 live births). Kidney, urinary tract, and bladder infections were the next most commonly listed subgroup, although the rate (533.4 hospitalizations per 100000 live births; 95% CI: 491.1-575.7 hospitalizations per 100000 live births) was much lower than the rate of LRTIs; this was followed by septicemia (457.5 hospitalizations per 100000 live births; 95% CI: 412.3–502.7 hospitalizations per 100000 live births) and upper respiratory tract infections (455.9 hospitalizations per 100000 live births; 95% CI: 426.3-485.5 hospitalizations per 100000 live births). The least commonly listed disease groups were tuberculosis (2.2 hospitalizations per 100000 live births; 95% CI: 1.4-3.0 hospitalizations per 100000 live births) and infections of the heart (1.3 hospitalizations per 100000 live births; 95% CI: 0.8-1.8 hospitalizations per 100000 live births).
With respect to age group, there were some differences in the proportions of ID hospitalizations attributable to various disease groups. Although LRTI was the most commonly listed disease group for both age groups, LRTIs accounted for 63.2 ± 0.4% of ID hospitalizations among postneonates and only 36.1 ± 0.8% of ID hospitalizations among neonates. Septicemia was the second most commonly reported disease group for neonate ID hospitalizations (28.6 ± 1.0%) but accounted for only 2.4 ± 0.1% of postneonate hospitalizations.
Differences in ID hospitalization rates according to race were also seen. Although Asian/Pacific Islander infants had lower rates of any first-listed ID hospitalization and meningitis, LRTI, upper respiratory tract infection, and viral central nervous system infection hospitalizations, compared with non-Hispanic white infants, the hospitalization rates for abdominal and rectal infections and for kidney, urinary tract, and bladder infections were higher. Non-Hispanic black infants and Hispanic infants had significantly higher hospitalization rates for cellulitis, enteric infections, LRTIs, mycoses, septicemia, upper respiratory tract infections, viral central nervous system infections, and infections specific to the perinatal period, compared with white infants. In addition, non-Hispanic black infants had higher hospitalization rates for meningitis.
Commonly Listed Diagnoses and Accompanying Procedures
Among infants hospitalized with a first-listed diagnosis of ID, the most commonly listed discharge diagnoses included RSV bronchiolitis (ICD-9-CM code 466.11; 23.5 ± 0.3%); acute bronchiolitis, organism not specified (ICD-9-CM code 466.19; 19.0 ± 0.3%); pneumonia, organism not specified (ICD-9-CM code 486; 13.2 ± 0.2%); volume depletion (ICD-9-CM code 276.5; 11.6 ± 0.2%); and otitis media, not otherwise specified (ICD-9-CM code 382.9; 11.2 ± 0.2%) (Table 4). Among neonates, the top diagnosis was RSV bronchiolitis (19.2 ± 0.4%) and other leading diagnoses included septicemia of newborn (ICD-9-CM code 771.81; 13.0 ± 0.6%); viral infection, not otherwise specified (ICD-9-CM code 079.99; 12.9 ± 0.5%); other infections specific to the perinatal period (ICD-9-CM code 771.89; 8.3 ± 1.1%); and unspecified septicemia (ICD-9-CM code 038.9; 8.0 ± 0.6%). The leading diagnoses for the postneonates were the same as those for all infant ID hospitalizations. Among all-cause infant hospitalizations, top diagnoses were volume depletion (11.9 ± 0.2%); RSV bronchiolitis (10.4 ± 0.2%); acute bronchiolitis, organism not specified (8.7 ± 0.2%); esophageal reflux (ICD-9-CM code 530.81; 8.1 ± 0.2%); and unspecified fetal and neonatal jaundice (ICD-9-CM code 774.6; 8.0 ± 0.2%). The top diagnoses among nonprimary ID hospitalizations were volume depletion (11.85 ± 0.23%), esophageal reflux (8.14 ± 0.21%), unspecified fetal and neonatal jaundice (7.97 ± 0.2%), and fever (ICD-9-CM code 780.6; 5.41 ± 0.13%). Procedures reported to have been performed most frequently during infant ID hospitalizations were lumbar puncture (ICD-9-CM code 033.1; 16.7 ± 0.5%), medication administered by using a nebulizer (ICD-9-CM code 939.4; 3.4 ± 0.5%), injection of antibiotic (ICD-9-CM code 992.1; 2.8 ± 0.4%), and venous catheterization not elsewhere classified (ICD-9-CM code 38.93; 2.2 ± 0.1%).
Hospital Length of Stay and Costs
A total of 1010675 ± 35472 hospitalization days were associated with all infant ID hospitalizations. The median length of stay in the hospital was 3 days (interquartile range: 2–4 days; mean: 3.52 days) (Table 2). Hospital costs for all infant ID hospitalizations totaled nearly 690 million dollars ($686206151 ± $34262585), which corresponded to total charges of nearly 3 billion dollars. The median estimated hospital cost for an ID hospitalization was $2235 (interquartile range: $1440–$3694; mean: $4036). The mean length of stay and costs were significantly greater for neonates than for postneonates (4.6 ± 0.1 and 3.3 ± 0.04 days, respectively, and $5716 ± $189 and $3748 ± $99; P < .001 for both).
During 2003, ∼290000 infant hospitalizations were for IDs in the United States. The ID hospitalization rate was 7010.8 hospitalizations per 100000 live births (95% CI: 6618.3–7403.3 hospitalizations per 100000 live births), or ∼1 ID hospitalization for every 14 infants. The infant ID hospitalization rate for 2003 had not changed from the rate reported for 1998 to 1999 (8996 hospitalizations per 100000 live births; 95% CI: 7313–10679 hospitalizations per 100000 live births) in an earlier study that used the National Hospital Discharge Survey.5 Neonates, boys, and nonwhite infants were at increased risk for ID hospitalization. Non-Hispanic black and Hispanic infants had higher overall ID hospitalization rates, compared with those for non-Hispanic white and Asian/Pacific Islander infants, as well as higher rates for many of the specific disease groups. Male gender and nonwhite race are both known risk factors for infant death and adverse birth outcomes (including low birth weight),24 which may influence the high rate of ID hospitalizations in this group. The discrepancy between black and white ID mortality rates has been documented for adults, even after adjustment for socioeconomic status.25 Other circumstances, such as caregivers' practices and lifestyle risk factors, and increased risks for specific IDs may be the reasons for the increased ID burden among nonwhite infants.
For all age groups, Medicaid was indicated as the primary payer for more than one half of ID hospitalizations, whereas private insurance/health maintenance organization was listed for 35.7%. In comparison, Medicaid accounted for a smaller proportion (40.8%) of all infant hospitalizations, whereas private insurance/health maintenance organization accounted for a larger proportion (51.5%). Furthermore, more than one third of the infants with ID hospitalizations were from areas where household incomes were less than $36000, and <16% were from areas with incomes of $60000 or more. The increased proportion of hospitalizations with lower reported income and with Medicaid as the primary payer among infants hospitalized with IDs presumably reflect disadvantaged social status.26 ID hospitalizations represented a major source of health care expenditures (both subsidized and private) among US infants, with >1 million total hospital days and more than $3 billion in total hospital charges for 2003. Limited access to preventive care resources such as vaccination might have influenced ID hospitalization rates and contributed to the higher rates among certain groups of infants. We did not address specifically the burden of hospitalization for vaccine-preventable diseases; however, this has been the subject of several studies27–32 and merits further research.
Respiratory diseases, particularly LRTIs (including bronchiolitis and pneumonia), were the primary contributors to ID hospitalizations among both neonates and older infants. RSV is the most common viral cause of LRTIs in infants10,33,34 and, consistent with our findings, RSV bronchiolitis was reported to be the leading primary diagnosis for hospital discharges among infants in previous years.35,36 Studies showed that the rate of bronchiolitis-associated hospitalizations increased among US infants during 1980 to 1996 and during 1999 to 2001, indicating a need for continued surveillance and research into potential vaccines and treatments.10,37
Kidney, urinary tract, and bladder infections were the next leading cause of ID hospitalizations among infants. Although this diagnosis is often suspected in the setting of fever of unknown origin,38,39 the diagnosis generally can be reliably made on the basis of laboratory diagnostic testing.40 Neonates are known to be at increased risk for kidney, urinary tract, and bladder infections, possibly because of an incompletely formed urinary tract.38,41 Some urinary tract infections may be nosocomially acquired,38,42 however, and whether such infections account in part for the high rate of ID hospitalizations listing kidney, urinary tract, and bladder infections as a discharge diagnosis in our study is not clear.
The next leading cause of hospitalization was septicemia, largely because of the high hospitalization rate among neonates. Septicemia is known to occur more frequently among low birth weight and preterm infants,11–13 which may account for the twofold increase in hospitalization rate for neonates, compared with older infants. Nearly three fourths of in-hospital deaths among neonates were attributable to sepsis of the newborn.
Infants in the second month of life constituted the largest group for infant ID hospitalizations; ID hospitalizations decreased with increasing age after the second month of life. There were also differences in the causes of ID hospitalizations according to age. Although the most commonly listed diagnosis for both neonates and postneonates was RSV bronchiolitis, the leading diagnoses for neonates included many perinatal period- and neonatal period-specific diagnoses. Among hospitalizations without a primary ID diagnosis indicated, the leading diagnoses did not include specific IDs. However, some of the most frequently listed diagnoses (volume depletion, unspecified fetal and neonatal jaundice, and fever) may reflect an underlying ID.
Our assessment has limitations. The reporting of infant ID hospitalizations may be affected by different reporting practices among the participating hospitals or by regional differences in admitting practices, and diagnoses may be incomplete or miscoded. It is not possible to identify a patient or to link the patient's hospitalization records in the KID, because patient identifiers are not available; therefore, readmissions would be included in this analysis. Our study was limited in its ability to distinguish primary admission IDs from those that might have been acquired nosocomially, because we relied on discharge data. Because some records were missing race/ethnicity information, we were limited in our ability to examine ID hospitalizations according to race/ethnicity and the hospitalization rates are underestimated. We did not examine hospitalization rates for infants with American Indian/Alaska Native race indicated, because race was not reported completely and there were few of these hospitalizations. Furthermore, the data did not include federal health care facilities, where most American Indian/Alaska Native patients access health care services.43 However, published rates of ID hospitalization among American Indian/Alaska Native infants indicated that the rate is higher than the rate for the general US infant population.5
This study provides a comprehensive assessment and national estimates of the burden and epidemiologic characteristics of ID hospitalizations among infants in the United States. ID hospitalizations among infants account for substantial health care expenditures and hospital resources. IDs, particularly respiratory diseases, cause substantial morbidity among infants. Younger infants, boys, and nonwhite infants are at increased risk for ID hospitalization. Additional efforts are needed to provide broader access to preventive services, to decrease health disparities, and to improve the health status for all infants in the United States.
We thank Andrew Mosso from Social and Scientific Systems for technical assistance, and we thank the states that participate in the HCUP to produce the KID.
- Accepted July 20, 2007.
- Address correspondence to Krista L. Yorita, MPH, Division of Viral and Rickettsial Diseases, National Center for Zoonotic, Vector-Borne, and Enteric Diseases, Centers for Disease Control and Prevention, Mail Stop A-39, Atlanta, GA 30333. E-mail:
The authors have indicated they have no financial relationships relevant to this article to disclose.
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the funding agencies.
- ↵Simonsen L, Conn LA, Pinner RW, Teutsch S. Trends in infectious disease hospitalizations in the United States, 1980–1994. Arch Intern Med.1998;158(17) :1923– 1928
- ↵Mackenbach JP. The epidemiologic transition theory. J Epidemiol Community Health.1994;48 (4):329– 331
- ↵Holman RC, Curns AT, Cheek JE, Singleton RJ, Anderson LJ, Pinner RW. Infectious disease hospitalizations among American Indian and Alaska Native infants. Pediatrics.2003;111 (2). Available at: www.pediatrics.org/cgi/content/full/111/2/e176
- ↵American Academy of Pediatrics, Subcommittee on Diagnosis and Management of Bronchiolitis. Diagnosis and management of bronchiolitis. Pediatrics.2006;118 (4):1774– 1793
- ↵Greenough A, Cox S, Alexander J, et al. Health care utilisation of infants with chronic lung disease, related to hospitalisation for RSV infection. Arch Dis Child.2001;85 (6):463– 468
- ↵Meissner HC. Selected populations at increased risk from respiratory syncytial virus infection. Pediatr Infect Dis J.2003;22(2 suppl) :S40– S44
- ↵Parrott RH, Kim HW, Arrobio JO, et al. Epidemiology of respiratory syncytial virus infection in Washington DC, part II: infection and disease with respect to age, immunologic status, race and sex. Am J Epidemiol.1973;98 :289– 300
- ↵Shay DK, Holman RC, Newman RD, Liu LL, Stout JW, Anderson LJ. Bronchiolitis-associated hospitalizations among US children, 1980–1996. JAMA.1999;282(15) :1440– 1446
- ↵Stoll BJ, Holman RC, Schuchat A. Decline in sepsis-associated neonatal and infant deaths in the United States, 1979 through 1994. Pediatrics.1998;102 (2). Available at: www.pediatrics.org/cgi/content/full/102/2/e18
- ↵Watson RS, Carcillo JA. Scope and epidemiology of pediatric sepsis. Pediatr Crit Care Med.2005;6(3 suppl) :S3– S5
- ↵Healthcare Cost and Utilization Project. Kid's Inpatient Database (KID), 2003. Rockville, MD: Agency for Healthcare Research and Quality; 2005
- ↵Public Health Service and Health Care Financing Administration. International Classification of Diseases, Ninth Revision, Clinical Modification. 6th ed. Washington, DC: Public Health Service and Health Care Financing Administration; 1997
- ↵Curns AT, Holman RC, Sejvar JJ, Owings MF, Schonberger LB. Infectious disease hospitalizations among older adults in the United States from 1990 through 2002. Arch Intern Med.2005;165(21) :2514– 2520
- ↵Healthcare Cost and Utilization Project. 2003 Kids' Inpatient Database Cost-to-Charge Ratio File. Rockville, MD: Agency for Healthcare Research and Quality; 2006
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- ↵US Department of Health and Human Services, National Center for Health Statistics. Detailed Data 2003: Public Use Data Tape Documentation: Natality. Hyattsville, MD: Centers for Disease Control and Prevention, National Center for Health Statistics; 2004.
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- ↵Davis MM, Patel MS, Gebremariam A. Decline in varicella-related hospitalizations and expenditures for children and adults after introduction of varicella vaccine in the United States. Pediatrics.2004;114 (3):786– 792
- Iwane MK, Edwards KM, Szilagyi PG, et al. Population-based surveillance for hospitalizations associated with respiratory syncytial virus, influenza virus, and parainfluenza viruses among young children. Pediatrics.2004;113 (6):1758– 1764
- ↵Tanaka M, Vitek CR, Pascual FB, Bisgard KM, Tate JE, Murphy TV. Trends in pertussis among infants in the United States, 1980–1999. JAMA.2003;290(22) :2968– 2975
- ↵Shay DK, Holman RC, Roosevelt GE, Clarke MJ, Anderson LJ. Bronchiolitis-associated mortality and estimates of respiratory syncytial virus-associated deaths among US children. J Infect Dis.2001;183 (1):16– 22
- ↵Holman RC, Curns AT, Cheek JE, et al. Respiratory syncytial virus hospitalizations among American Indian and Alaska Native infants and the general United States infant population. Pediatrics.2004;114 (4). Available at: www.pediatrics.org/cgi/content/full/114/4/e437
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