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Respiratory Viruses

This guide covers viral respiratory infections, including influenza, RSV, and other influenza-like illnesses (ILI)

U.S. Weekly ILI Report

U.S. Outpatient Respiratory Illness Surveillance

The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for respiratory illness referred to as influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and will therefore capture respiratory illness visits due to infection with pathogens that can present with similar symptoms, including influenza viruses, SARS-CoV-2, and RSV.

It is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a more complete and accurate picture of influenza, SARS-CoV-2, and other respiratory virus activity.

CDC is providing integrated information about COVID-19, influenza and RSV activity on a website that is updated weekly. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.

U.S. Weekly Influenza-like Illness Update

Last Updated: March 8, 2024

Nationwide, during Week 9, 4.1% of patient visits reported through ILINet were due to respiratory illness that included fever plus a cough or sore throat, also referred to as ILI. This has decreased (change of > 0.1 percentage points) compared to Week 8. The percentage of visits for ILI remained stable in regions 2, 3, 5, and 7, and decreased in regions 1, 4, 6, 8, 9, and 10 in Week 9 compared to Week 8. Regions 8 and 10 are below their region-specific baselines in Week 9 for the first time since early and mid-November respectively, while all other regions remain above their region-specific baselines. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI varies by location.

Weekly U.S. ILINet Map
Week , ending March 2, 2024

New York State Weekly ILI Report

The ILINet Program consists of healthcare providers in NYS (excluding NYC) that voluntarily report aggregate data for the total number of visits and the total number of visits of ILI in an outpatient setting.

Latest Data: Week 9, ending March 2, 2024

NYC ILI Weekly Report

NYC participates in the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet), which is coordinated nationally by Centers for Disease Control and Prevention. This system monitors the proportion of patients presenting with ILI each week at emergency departments, urgent care centers, and primary care clinics. ILINet monitors visits for ILI, not laboratory-confirmed influenza, and may capture patient visits due to other respiratory pathogens that cause similar symptoms.


Latest Data: Week 9, ending March 2, 2024