The National Hospital Ambulatory Medical Care Survey (NHAMCS) has been fielded annually since 1992 to collect data on the utilization and provision of ambulatory care services in hospital emergency and outpatient departments. Data collection from hospital-based ambulatory surgery centers began in 2009. And between 2010 and 2012 NHAMCS gathered data on visits to freestanding ambulatory surgery centers. In 2018, the survey began focusing on just the ambulatory visits made to emergency departments.
Each emergency department is randomly assigned to a 4-week reporting period. During this period, data for a systematic random sample of visits are recorded by Census interviewers using a computerized Patient Record Form. Data are obtained on patient characteristics such as age, sex, race, and ethnicity, and visit characteristics such as patient’s reason for visit, provider’s diagnosis, services ordered or provided, and treatments, including medication therapy. In addition, data about the facility are collected as part of a survey induction interview.

2023 Respiratory Virus Response - NSSP Emergency Department Visits - COVID-19, Flu, RSV, Combined


For additional information, please see: Companion Guide: NSSP Emergency Department Data on Respiratory Illness

2023 Respiratory Virus Response - NSSP Emergency Department Visits - COVID-19, Flu, RSV, Combined – by Demographic Category

Updated once per week on Fridays.

2023 Respiratory Virus Response - NSSP Emergency Department (ED) Visit Trajectories by State and Sub-State Regions- COVID-19, Flu, RSV, Combined. This dataset provides the percentage of emergency department patient visits for the specified pathogen of all ED patient visits for the specified geographyeach part of the country that were observed for the given week from data submitted to the National Syndromic Surveillance Program (NSSP). In addition, the trend over time is characterized as increasing, decreasing or no change, with exceptions for when there areis no data available, or the data are too sparseor there are not enough data to compute a trend. These data are to provide awareness of how the weekly trend is changing for the given geographic region. 

Note that the reported sub-state trends are from Health Service Areas (HSA) and the data reported from the health care facilities located within the given HSA. Health Service Areas are regions of one or more counties that align to patterns of care seeking. The HSA level data are reported for each county in the HSA.

For the emergency department time series, trajectory classifications reported on for sub-state (HSA) emergency department time series, trajectory classifications are based on approximations of the first derivative (slope) of trends that are smoothed using generalized additive models (GAMs). To determine time intervals in which the slope is sufficiently changing (i.e., rate of change distinguishable from 0), 95% confidence intervals for the slope approximations are calculated and assessed. Weeks with a 95% confidence interval not containing 0 are classified as increasing if the slope estimate is positive and decreasing if the slope estimate is negative. Weeks with a 95% confidence interval containing 0 are classified as stable. In the scenario that an HSA's time series is determined to be too sparse (i.e., many weeks with percentages of 0%), a model is not fit, and the HSA is classified as “sparse”.


For additional information, please see: Companion Guide: NSSP Emergency Department Data on Respiratory Illness


Updated once per week on Fridays. 

2023 Respiratory Viruses Response – National Syndromic Surveillance Program Emergency Department Visit Trajectories - COVID-19, Flu, RSV, Combined – by state. This dataset provides the percentage of emergency department patient visits for the specified pathogen of all ED patient visits for the specified geography that were observed for the given week from data submitted to the National Syndromic Surveillance Program (NSSP). In addition, the trend over time both as of the given row date and as of the most current data submitted is characterized as increasing, decreasing or stable to provide awareness of how the weekly trend is changing for the given geographic region.

For the emergency department time series, trajectory classifications reported on the opening page are based on rolling regression model assessments of the slope for each respiratory illness. Weeks with a significant time term (p <0.05) are classified as increasing when the slope is positive and decreasing when the slope is negative. Weeks with a non-significant time term (p ≥ 0.05) are classified as stable. A 3-week moving average is applied to the time series prior to the regression procedure in order to smooth week-to-week variation.


For additional information, please see:Companion Guide: NSSP Emergency Department Data on Respiratory Illness


Updated once per week on Fridays.

The National Hospital Ambulatory Medical Care Survey (NHAMCS) has been fielded annually since 1992 to collect data on the utilization and provision of ambulatory care services in hospital emergency and outpatient departments. Data collection from hospital-based ambulatory surgery centers began in 2009. And between 2010 and 2012 NHAMCS gathered data on visits to freestanding ambulatory surgery centers. In 2018, the survey began focusing on just the ambulatory visits made to emergency departments.
Each emergency department is randomly assigned to a 4-week reporting period. During this period, data for a systematic random sample of visits are recorded by Census interviewers using a computerized Patient Record Form. Data are obtained on patient characteristics such as age, sex, race, and ethnicity, and visit characteristics such as patient’s reason for visit, provider’s diagnosis, services ordered or provided, and treatments, including medication therapy. In addition, data about the facility are collected as part of a survey induction interview.