South Carolina Influenza Activity and Surveillance:
2008-2009 Season
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1. SC Flu Activity Status for MMWR Week 1 (January 4-January 10): SPORADIC
Influenza vaccine never covers all circulating strains of influenza, but does make illness milder or prevent the flu in most cases. CDC stresses that it is never too late to vaccinate.
- Map of positive cultures by county (updated 1/10/2009)
Interpretation: SC Viral Isolate Activity: Three positive cultures have been reported thus far. The BOL has tested 88 specimens from October 4, 2008 to January 10, 2008.
Map of positive rapid influenza tests by county (updated 1/10/2009)
Interpretation: There were 55 positive tests reported from January 4 - January 10. Update from MMWR Week 53 (12/28-1/03): There were 44 positive tests reported.- Report of SC positive rapid influenza tests in the 2006-07 and 2007-08 seasons. (pdf)
- Map of ILI activity by county (updated 1/10/2009)
Interpretation: ILI Activity Status (South Atlantic ILI baseline is 2.2%): BELOW baseline in the Upstate (.48%) Midlands (.53%) and along the Coast (2.0%). State ILI is .72%.
- 2007-08 weekly ILI activity compared to 2008-09 weekly ILI activity (updated 1/10/2009)
- Previous weekly influenza surveillance reports
- 2007-2008 Flu Maps
- 2006-2007 Flu Maps
- 2005-2006 Flu Maps
- 2004-2005 Flu Maps
US Influenza Activity: www.cdc.gov/flu/weekly
Current pandemic phase, as defined by the World Health Organization
(WHO), is:
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Human infection(s) with a new subtype but no human-to-human spread, or at most rare instances
of spread to a close contact.
2. What does “influenza activity” mean?
State health departments report the estimated level of influenza activity in their states each week. 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 Influenza-like Illness (ILI).
- Sporadic: Small numbers of laboratory-confirmed influenza cases or a single influenza outbreak has been reported, but there is no increase in cases of Influenza-like Illness.
- Local: Outbreaks of influenza or increases in Influenza-like Illness cases and recent laboratory-confirmed influenza in a single region of the state.
- Regional: Outbreaks of influenza or increases in Influenza-like Illness and recent laboratory confirmed influenza in at least 2 but less than half the regions of the state.
- Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state.
3. How many cases of influenza do we have?
Surveillance cannot tell us how many cases of influenza there are in South Carolina because not everyone who has influenza goes to the doctor. Surveillance can tell us the trend of influenza in South Carolina. Based on previous years data, it is estimated that ten percent of the South Carolina population (about 400,000) will have influenza by the end of the season.
It is important to remember the following about influenza surveillance in the United States:
- The reported information answers the questions of where, when, and what influenza viruses are circulating. It can be used to determine if influenza activity is increasing or decreasing, but cannot be used to ascertain how many people have become ill with influenza during the influenza season.
- Other conditions commonly have influenza-like symptoms, but are not influenza. Unusual clusters of respiratory illness are reportable by hospitals and physician offices by phone based upon our current List of Reportable Conditions (pdf).
4. What is Influenza Surveillance?
Influenza surveillance allows South Carolina and the CDC to monitor influenza activity and see how it impacts the health of South Carolinians. Surveillance allows doctors to know the influenza activity in their community and make better diagnosis and treatment decisions for their patients.
South Carolina uses three different surveillance systems, each giving different types of information about influenza, but together they create a better overview of influenza activity in the state. This three-part surveillance system allows us to:
- Identify whether the influenza virus is the cause of influenza-like symptoms in people,
- Tell when the influenza virus first appears in the state, and also when it decreases,
- Where in the state the influenza virus is circulating, and
- Estimate how many actually have influenza of those that visit their physician with influenza-like illness (ILI).
Surveillance cannot tell us exactly how many cases of influenza there are in the state because not everyone who gets the influenza goes to the doctor to get tested. The types of Influenza virus that infect people often change every influenza season. Influenza surveillance can tell us what new influenza virus types are in South Carolina. We use the new influenza virus information to help make vaccines for next year’s influenza season.
5. How do we get surveillance information?
Three pieces to the puzzle, three “sources of data”:
Positive Influenza Viral Cultures
Why do we do viral cultures? Virus culture is the gold standard in confirming cases of influenza type -A and -B because it is more sensitive than rapid influenza tests. Identification of the particular strain of influenza is available only through this method, and can aid in outbreak tracking. Viral culture can also be used to identify other viruses that cause clinical symptoms similar to influenza.
What does a positive culture mean? A positive culture result indicates that the influenza virus has been isolated from a swab of the patient's throat, and confirms an influenza infection.
Rapid Influenza Testing
Why do we do Rapid Influenza Testing? Rapid influenza tests are mostly used in doctors’ office settings and emergency departments. Rapid flu tests are a tool that can help quickly diagnose influenza in a patient with symptoms, usually within 30 minutes.
What does a positive rapid flu test mean? Positive rapid flu tests indicate flu virus is present. A positive test tells us that a person’s symptoms are being caused by the influenza virus and not by any of the other respiratory viruses that cause influenza-like symptoms. Depending on the brand of rapid influenza test kit used, a positive test can tell if the influenza virus present is type A, type B, or both. Of course, a doctor uses a positive test result, as well as other clinical information to make a decision on the best treatment.
Influenza-like illness (ILI) reports
Why do we use sentinel providers? Influenza-like Illness (ILI) is defined as having a fever > 100°F AND cough and/or sore throat when there is no other cause found for having those symptoms. Health care providers who volunteer to report ILI cases are called Sentinel providers. Sentinel providers report weekly the percentage of their patients presenting with ILI. This is critical for monitoring the impact of influenza in South Carolina.
What does an ILI report mean? An influenza-like illness report means it is likely the person has influenza even if the doctor does not perform a lab test that day. If influenza is already known to be in that person’s community their symptoms are more likely to be caused by influenza.
6. Information for health care professionals
- Archived Health Alert Network surveillance
- CDC Flu Website
- World Health Organization (WHO) – International Avian influenza information
- South Carolina Influenza (Flu) Plan
7. Avian Influenza information
- (CDC) Avian Flu Website
- Avian Influenza Information - Clemson Livestock and Poultry Health
- Health Care Professional Information - (CDC) Avian flu site
- (DHEC) Avian Flu Information
- South Carolina's Mass Casualty plan includes the state's plans for the Strategic National Stockpile and Pandemic Influenza.
- DHEC Public Health Preparedness
- U.S. Government Avian and Pandemic Flu Information
9. NEW World Health Organization Stages of a Pandemic (CDC) - Pandemic Response Phase Definitions
10. Links to other resources for information about influenza
- SC Health Alert Network - for the latest advisories and updates about influenza
- Centers for Disease Control and Prevention (CDC) – Influenza resources
- Centers for Disease Control and Prevention (CDC) – Current National Influenza Activity
- Centers for Disease Control and Prevention (CDC) – Traveler’s Health
- Centers for Disease Control and Prevention (CDC) – General Immunization information
- U.S. Food and Drug Administration (FDA) – Vaccine Information
- World Health Organization – International influenza information
- General Influenza (Flu) Immunization Information (DHEC)