What does sporadic mean for flu season?

Answer 1

When diseases are described as sporadic in medical contexts it means that the disease is occurring in single cases here and there and scattered groups of cases. For the flu it can indicate the beginning of an epidemic before cases are widespread or it can be describing when the cases are slowing down and the flu is beginning to have run its course and the epidemic may be coming to an end. Since influenza viruses tend to spread in multiple outbreaks (in "waves"), it may also indicate that at least that particular wave of the outbreak is in the final stages.

This term has a specific definition from the Centers for Disease Control and Prevention (CDC) for use in their "Influenza Like Illness" (ILI) surveillance reports. Definitions from the CDC are provided below. See the related links section below for a link to the full information from CDC on how the weeky surveillance reports of ILI are developed, etc.

From the CDC:

Summary of the Geographic Spread of Influenza - State health departments report the estimated level of spread of influenza activity in their states each week through the State and Territorial Epidemiologists Reports. States report influenza activity as no activity, sporadic, local, regional, or widespread. These levels are defined as follows:

• No Activity: No laboratory-confirmed cases of influenza and no reported increase in the number of cases of ILI.

• Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

• Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.

• Regional:Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions.

• Widespread:Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.