Emergency Department Visits for Influenza and Pneumonia: United States, 2016–2018

● The ED visit rate for patients with influenza and pneumonia was higher for persons with Medicare (19.9 per 1,000 persons with Medicare) or Medicaid (26.2 per 1,000 persons with Medicaid) compared with persons with private insurance or uninsured persons. In the United States, there were an estimated 810,000 hospitalizations attributable to influenza during 2017–2018 (1). Pneumonia is the most common respiratory complication of influenza (2). In 2019, the ninth leading cause of death was influenza and pneumonia and the death rate was 15.2 per 100,000 persons, ranging from 4.1 for infants aged under 1 year to 294.7 for adults aged 85 and over (3,4). This report describes emergency department (ED) visit rates for patients with influenza and pneumonia (either influenza or pneumonia, or both) by selected patient characteristics.

In the United States, there were an estimated 810,000 hospitalizations attributable to influenza during 2017-2018 (1). Pneumonia is the most common respiratory complication of influenza (2). In 2019, the ninth leading cause of death was influenza and pneumonia and the death rate was 15.2 per 100,000 persons, ranging from 4.1 for infants aged under 1 year to 294.7 for adults aged 85 and over (3,4). This report describes emergency department (ED) visit rates for patients with influenza and pneumonia (either influenza or pneumonia, or both) by selected patient characteristics.

What were the ED visit rates for influenza and pneumonia in 2016-2018?
• In 2016-2018, the ED visit rate for patients with pneumonia was 7.9 per 1,000 persons, which was higher than the ED visit rate for patients with influenza (4.4 per 1,000 persons) ( Figure 1).  1 Significantly different from ED visit rates for pneumonia (p < 0.0001). NOTES: Based on a sample of 1,532 emergency department (ED) visits made by patients with a diagnosis of influenza or pneumonia (ICD-10-CM, J09-J18), representing an annual average of approximately 3.9 million ED visits (2.8% of all ED visits). The influenza category and the pneumonia category are not mutually exclusive; influenza visits include visits with diagnoses of influenza due to identified novel influenza A virus with pneumonia (ICD-10-CM, J09.X1), influenza due to other identified influenza virus with pneumonia (ICD-10-CM, J10.0), and influenza due to unidentified influenza virus with pneumonia (ICD-10-CM, J11.0). Visit rates use sets of estimates of the U.S. civilian noninstitutionalized population developed by the U.S. Census Bureau and reflect the population as of July 1 of each year during 2016-2018. Access data table for Figure 1

Did the ED visit rate for influenza and pneumonia differ by age?
• During 2016-2018, the ED visit rate for patients with influenza and pneumonia varied by age. Among children aged 0-17 years, the ED visit rate decreased from 34.7 visits per 1,000 children under age 5 to 10.7 visits per 1,000 children aged 5-17. (Figure 2).
• Among adults, the ED visit rate for patients with influenza and pneumonia increased with age, ranging from 7.1 per 1,000 adults aged 18-44 to 45.6 per 1,000 adults aged 85 and over.

Did the ED visit rate for influenza and pneumonia differ by race and ethnicity?
• During 2016-2018, the ED visit rate for patients with influenza and pneumonia was highest among non-Hispanic black persons (21.9 per 1,000) compared with non-Hispanic white (11.8), non-Hispanic other (6.6), and Hispanic (9.8) persons ( Figure 3).
• The ED visit rate for patients with influenza and pneumonia was higher among non-Hispanic white persons (11.8 per 1,000) compared with non-Hispanic persons of other races (6.6).

Did the ED visit rate for influenza and pneumonia differ by primary expected source of payment?
• The ED visit rate for patients with influenza and pneumonia was higher for persons with Medicare or Medicaid as their primary expected source of payment (19.9 visits per 1,000 persons with Medicare and 26.2 visits per 1,000 persons with Medicaid) compared with persons with private insurance as their primary expected source of payment (5.0) or uninsured persons (7.0) (Figure 4).
• The observed difference in ED visit rates between Medicare and Medicaid as an expected source of payment was not significant.

Summary
This report examined ED visit rates for influenza and pneumonia during 2016-2018. Differences by age, race and ethnicity, and primary expected source of payment were identified. The ED visit rate for patients with influenza and pneumonia was higher among children under age 5 compared with children aged 5-17 and increased with age among adults. Among adults, the rate was highest among those aged 85 and over. The ED visit rate was higher among non-Hispanic black persons than among other race and ethnicity groups. The ED visit rate for patients with influenza and pneumonia was highest for persons with Medicare or Medicaid compared with persons with private insurance or uninsured persons. With the recent spread of COVID-19, which has signs and symptoms that can mirror or appear similar to those resulting from influenza and pneumonia, monitoring ED visits for influenza and pneumonia will continue to be important. Primary expected source of payment: During data collection, all sources of payment were collected. For patients with more than one source of payment, sources were collapsed into one mutually exclusive variable (primary expected source of payment) based on the hierarchy below:

Definitions
• Medicare: Partial or full payment by Medicare plan includes payments made directly to the hospital or reimbursed to the patient. Charges covered under a Medicare-sponsored prepaid plan are included. • Uninsured: Only self-pay, no charge, or charity as primary expected source of payment. Self-pay are charges that are paid by the patient or patient's family, which will not be reimbursed by a third party. Self-pay includes visits for which the patient is expected to be ultimately responsible for most of the bill, even if the patient never actually pays it. This does not include copayments or deductibles. No charge or charity are visits for which no fee is charged (for example, charity, special research, or teaching).

Data source and methods
Data for this report are from the National Hospital Ambulatory Medical Care Survey (NHAMCS), an annual nationally representative survey of nonfederal, general, and short-stay hospitals. NHAMCS uses a multistage probability design with samples of geographic primary sampling units (PSUs), hospitals within PSUs, and patient visits within EDs. Additional information on the methodology of NHAMCS has been previously described (6,7). This report presents results combining data for 2016-2018 to enable more detailed subgroup analyses. Estimates of the weighted number of visits are based on 3-year annual averages. Data analyses were performed using the statistical packages SAS version 9.4 (SAS Institute, Cary, N.C.) and SAS-callable SUDAAN version 11.0 (RTI International, Research Triangle Park, N.C.). All percentage estimates presented meet National Center for Health Statistics (NCHS) guidelines for presentation of proportions (8) and follow NCHS trend analysis guidelines (9). Linear trends by age among adults were evaluated using linear regression. Differences between trends were evaluated using a two-sided significance test at the 0.05 level.