Respiratory Virus Activity Levels
Provides an update on how COVID-19, influenza, and RSV may be spreading nationally and in your state.
- The amount of respiratory illness (fever plus cough or sore throat) causing people to seek healthcare continues to decrease across most areas of the country. This week, 0 jurisdictions experienced high activity compared to 1 jurisdiction experiencing high activity the previous week. No jurisdictions experienced very high activity.
- Nationally, emergency department visits with diagnosed influenza are decreasing. Emergency department visits with COVID-19 and RSV remain stable at low levels.
- Nationally, COVID-19, influenza, and RSV test positivity decreased compared to the previous week.
- Nationally, the COVID-19 wastewater viral activity level, which reflects both symptomatic and asymptomatic infections, remains low.
Reported on Friday, April 26th, 2024.
Level of Respiratory Illness Activity
Activity levels determined weekly based on the percentage of visits to enrolled outpatient healthcare providers or emergency departments for fever and cough or sore throat reported to ILINet. Visits can be attributed to a variety of respiratory pathogens that cause these symptoms. Activity levels reflect how the percentage in the most recent week compares to what that jurisdiction typically experiences during low circulation periods. Trend information for the percentages used to calculate activity levels can be found at: National, Regional, and State Level Outpatient Illness and Viral Surveillance (cdc.gov).
- Source: U.S. Outpatient Influenza-Like Illness Surveillance Network (ILINet).
- Additional information available at: Outpatient Illness Surveillance methods section.
- This system monitors visits for respiratory illness that includes fever plus a cough or sore throat, (also referred to as influenza-like illness, or ILI), not laboratory confirmed infections; therefore, patient visits due to a variety of respiratory pathogens that cause similar symptoms may be captured.
- The activity levels compare the mean reported percent of visits due to ILI during the current week to the mean reported percent of visits due to ILI during non-influenza weeks. The 13 activity levels correspond to the number of standard deviations below, at, or above the mean for the current week compared with the mean during non-influenza weeks.
- This map uses the proportion of visits to enrolled outpatient healthcare providers or emergency departments for respiratory illness to measure the activity level within a state. It does not, however, measure the extent of geographic spread of respiratory illness within a state. Therefore, outbreaks occurring in a single city could cause the state to display high activity levels.
- Data collected in ILINet may disproportionately represent certain populations within a state depending on enrolled providers, and therefore may not accurately depict the full picture of respiratory virus activity for the whole state.
- The data presented in this map is preliminary and may change as more data is received.
- Differences in the data presented by CDC and state health departments likely represent differing levels of data completeness with data presented by the state likely being the more complete.
Emergency Department Visits for Viral Respiratory Illness
Weekly percent of total emergency department visits associated with COVID-19, influenza, and RSV.
- Source: National Syndromic Surveillance Program: https://www.cdc.gov/nssp/index.html
- There are no data available for the following states/territories: Guam, Missouri, New Hampshire, and South Dakota.
- Combined is the sum of COVID-19, influenza, and respiratory syncytial virus (RSV) emergency department visits.
- Additional information available at: Companion Guide: NSSP Emergency Department Data on Respiratory Illness
Percent of Tests Positive for Respiratory Viruses
Weekly percent of tests positive for the viruses that cause COVID-19, influenza, and RSV at the national level. Preliminary data are shaded in gray.
- Sources: COVID-19 and RSV: National Respiratory and Enteric Virus Surveillance System (NREVSS), a sentinel network of laboratories located through the US, includes clinical, public health and commercial laboratories; additional information available at: https://www.cdc.gov/surveillance/nrevss/index.html. Influenza: Clinical laboratory test results from NREVSS and U.S. World Health Organization collaborating laboratories; more details about influenza virologic surveillance are available here: https://www.cdc.gov/flu/weekly/overview.htm.
- Data for recent weeks in gray may be incomplete due to delays in reporting. These preliminary may change as more data become available.
- Data represent laboratory tests performed, not individual people.
- The data are from across the country in all regions.
- The percent of tests positive is calculated by dividing the number of positive tests by the total number of tests administered, then multiplying by 100 [(# of positive tests/total tests) x 100].
- COVID-19: The condition caused by infection with severe acute respiratory syndromic coronavirus type-2 (SARS-CoV-2).
- RSV and COVID-19 are limited to nucleic acid amplification tests (NAATs), also listed as polymerase chain reaction tests (PCR).
- Participating laboratories report weekly to CDC the total number of RSV tests performed that week and the number of those tests that were positive. The RSV trend graphs display the national average of the weekly % test positivity for the current, previous, and following weeks in accordance with the recommendations for assessing RSV trends by percent ( https://academic.oup.com/jid/article/216/3/345/3860464).
- COVID-19 laboratory data are available for download here: https://data.cdc.gov/Laboratory-Surveillance/Percent-Positivity-of-COVID-19-Nucleic-Acid-Amplif/gvsb-yw6g
- RSV laboratory data are available for download here: https://data.cdc.gov/Laboratory-Surveillance/Percent-Positivity-of-Respiratory-Syncytial-Virus-/3cxc-4k8q
COVID-19 Wastewater Trends
COVID-19 Wastewater Monitoring at the national and regional level. Preliminary data are shaded in gray.
Wastewater (sewage) can be tested to detect traces of infectious diseases circulating in a community, even if people don’t have symptoms. You can use these data as an early warning that levels of infections may be increasing or decreasing in your community. Wastewater trends may differ from some health outcome findings, such as hospitalization trends, as COVID-19 is causing severe disease less frequently than earlier in the pandemic.
This chart shows national and regional trends over time of the levels of SARS-CoV-2 (the virus that causes COVID-19) activity levels present in samples of wastewater taken from sites across the United States. Wastewater monitoring can detect viruses spreading from one person to another within a community earlier than clinical testing, and before people who are sick go to their doctor or hospital. It can also detect infections without symptoms. If you see increased Wastewater Viral Activity Levels of SARS-CoV-2, it might indicate that there is a higher risk of infection. See how to protect yourself from respiratory viruses like COVID-19.
The Wastewater Viral Activity Level shows changes in SARS-CoV-2 virus levels in wastewater compared to the baseline level for each wastewater treatment plant. National and regional data represent the median values across all wastewater treatment plants in the respective area. The Wastewater Viral Activity Levels are categorized into minimal, low, moderate, high, or very high as follows:
- Less than 1.5 – Minimal
- Greater than 1.5 and up to 3 – Low
- Greater than 3 and up to 4.5 – Moderate
- Greater than 4.5 and up to 8 – High
- Greater than 8 – Very High
For more information, see Data Methods.
States and territories are grouped into the following U.S Census Bureau regions:
- West: Alaska, Arizona, California, Colorado, Guam, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming (N=14)
- Midwest: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin (N=12)
- Northeast: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Puerto Rico, Rhode Island, Vermont (N=10)
- South: Arkansas, Alabama, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, West Virginia (N=17)