Weekly National Summary of Week 50: Outpatient Illness Surveillance, Geographic Spread, Mortality Surveillance
ILINet
Nationwide during week 50, 3.9% of patient visits reported through the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) were due to influenza-like illness (ILI). This percentage is above the national baseline of 2.4%.

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On a regional level, the percentage of outpatient visits for ILI ranged from 1.9% to 7.8% during week 50. All regions reported a percentage of outpatient visits for ILI which is equal to or above their region-specific baselines.
ILI Activity Map
Data collected in ILINet are used to produce a measure of ILI activity* by state.
During week 50, the following ILI activity levels were experienced:
- High – Puerto Rico, New York City, and 19 states (Alabama, Arizona, Arkansas, Colorado, Florida, Georgia, Kansas, Kentucky, Maryland, Mississippi, Nebraska, New Mexico, Oklahoma, Oregon, South Carolina, Tennessee, Texas, Virginia, and Washington)
- Moderate – the District of Columbia and six states (Connecticut, Illinois, Minnesota, New Jersey, North Carolina, and North Dakota)
- Low – 10 states (California, Hawaii, Indiana, Massachusetts, Nevada, New York, Pennsylvania, Utah, Wisconsin, and Wyoming)
- Minimal – 14 states (Alaska, Delaware, Idaho, Iowa, Maine, Michigan, Missouri, Montana, New Hampshire, Ohio, Rhode Island, South Dakota, Vermont, and West Virginia)
- Data were insufficient to calculate an ILI activity level from the U.S. Virgin Islands and Louisiana.
*Data collected in ILINet may disproportionately represent certain populations within a state, and therefore, may not accurately depict the full picture of influenza activity for the whole state. Differences in the data presented here by CDC and independently by some state health departments likely represent differing levels of data completeness with data presented by the state likely being the more complete.
Additional information about medically attended visits for ILI for current and past seasons:
Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map
Geographic Spread of Influenza as Assessed by State and Territorial Epidemiologists
The influenza activity reported by state and territorial epidemiologists indicates geographic spread of influenza viruses but does not measure the severity of influenza activity.
During week 50 the following influenza activity was reported:
- Widespread – Puerto Rico and 30 states (Alabama, Alaska, Arizona, California, Connecticut, Delaware, Florida, Georgia, Idaho, Indiana, Kentucky, Louisiana, Maryland, Massachusetts, Minnesota, Mississippi, Montana, Nebraska, Nevada, New Mexico, New York, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, and Washington)
- Regional – 17 states (Arkansas, Colorado, Illinois, Iowa, Kansas, Maine, Michigan, Missouri, New Hampshire, New Jersey, North Dakota, Oklahoma, Rhode Island, South Dakota, Utah, Wisconsin, and Wyoming)
- Local – the District of Columbia and two states (Vermont and West Virginia)
- Sporadic – the U.S. Virgin Islands and one state (Hawaii)
- Guam did not report.
Additional geographic spread surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive
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