Influenza Surveillance Program for 2007 - 2008

The Maryland Department of Health and Mental Hygiene (DHMH) collects and reports information on influenza activity in the state each year from October through mid-May (Weeks 40 through 20). This year, the yearly flu season begins on September 30, 2007, and ends on May 18, 2008.

Influenza Surveillance is designed to:

The five components of influenza surveillance in Maryland are:

1. Reports from the DHMH Laboratories Administration and Sentinel Laboratories.

The DHMH Laboratories Administration and Sentinel Laboratories report the number of respiratory specimens that test positive for influenza types A and B each week. These tests may include rapid diagnostic tests, real-time polymerase chain reaction (RT-PCR), immunofluoresence and viral culture. The laboratories also report demographic information such as the patient's age and gender from whom the sample was collected. A subset of the influenza viruses isolated in culture is sent to the Centers for Disease Control and Prevention (CDC) for further classification. The CDC determines the exact strain of the virus.
   
2. U.S. Influenza Sentinel Provider Surveillance Network.

The Maryland DHMH and select health care providers participate in a national surveillance program in collaboration with the CDC and other state health departments. Sentinel Providers report the total number of patients seen each week and the number of those patients with influenza-like illness (ILI) by age group. ILI is defined by CDC as fever greater than or equal to 100°F AND cough and/or sore throat (in the absence of a known cause). The percent of patient visits for influenza-like illness is calculated and reported. NOTE: National baseline ILI rates should not be applied to state or regional data.

Attention Healthcare Providers: DHMH is always interested in making the Maryland Sentinel Provider Network stronger through the recruitment and retention of sentinel providers. If you are a healthcare provider, please see the linked document below for information on how you can become a sentinel provider.

Information about the US Influenza Sentinel Provider Network and how you can join
   
3. State and Territorial Epidemiologists' Reports.

Maryland, along with the other state health departments, reports the estimated level of influenza each week to the CDC. Influenza activity is reported as no activity, sporadic, local, regional, or widespread, based on criteria applied to the collected information from laboratories, sentinel providers, and outbreak investigations. NOTE: The activity level is an indicator of geographic spread of activity not the strength or virulence of the current circulating strains.

Definition of Influenza Activity Levels
 
4. Outbreaks of Laboratory-Confirmed Influenza or Influenza-Like Illness.

Local health departments report outbreaks of laboratory-confirmed influenza or influenza-like illness in nursing homes and other institutional settings to DHMH. These reports are tallied from week to week and included in the weekly report for the state. And the number and location of the outbreaks is taken into consideration for determining the activity level of influenza in the state (SEE #3 ABOVE).

5. Cases of Influenza-Related Health Events

During the 2007-2008 season, the Emerging Infections Program in Maryland will be monitoring...

• Healthcare worker hospitalizations in the metropolitan Baltimore area caused by influenza, and
• Results of the flu vaccination program for school children.
• Summaries of any findings will be provided during the season as they become available.
  

It is important to remember the following about influenza surveillance:

All influenza reporting by laboratories and health care providers is voluntary. The reported information answers some questions of where, when, and which influenza viruses are circulating. The information is not representative of the state’s population. Therefore, it cannot be used to tell how many people have become ill with influenza during the season or project the exact distribution within the state.

REPORT FOR WEEK 18 (4/27/08 – 5/3/08):

LAB REPORTS – RAPID TESTS: This week, a total of 91 rapid influenza tests were performed by 11 sentinel laboratories.* Of these, 3 (3.3%) tests were positive. This represents a similar percent positive from last week (3.3%). NOTE: The DHMH Laboratory confirmed the season’s first case on 12/6/07, making all cases with a positive rapid influenza test count as confirmed cases for surveillance purposes. *NOTE: Thirteen participating labs in 7 counties did not report their observations as of the deadline of this report. LAB REPORTS – REFERENCE TESTS: The DHMH Laboratory reported 0 influenza isolate this week. PCR and viral isolation methods are considered to be “reference tests” or the “gold standard”; their results are more reliable than the rapid screening tests, whose positive predictive value is dependent on prevalence. *(Based on information from the World Health Organization, available at www.who.int/csr/disease/avian_influenza/guidelines/RapidTestInfluenza_web.pdf) To date this season, there have been 3638 lab-confirmed influenza cases in Maryland (3408 rapids, and 230 by DHMH Lab). Note: This is a revised count, compared to last week.	Click on graph to enlarge Click on graph to enlarge
INFLUENZA LIKE ILLNESS (ILI) REPORTS – This week, the median ILI percent reported by sentinel providers in Maryland was 0.9%. This is below the state baseline of 4.15%. However, only 5 of 32 providers reported their information. NOTE: Twenty-seven participating providers in 12 counties did not report their activity as of the publication deadline for this report.	Click on graph to enlarge
Based on the information gathered through the influenza surveillance program, the activity level for Maryland is “LOCAL” for Week 18.	Maryland Influenza Activity Levels: Week Ending Reported Influenza Activity 05/03/08 Local 04/26/08 Local 04/19/08 Local 04/12/08 Sporadic 04/05/08 Widespread 03/29/08 Regional 03/22/08 Regional 03/15/08 Regional
No outbreaks of influenza/influenza-like illness in institutional settings were reported to DHMH during Week 18. To date, 60 institutional outbreaks of influenza and/or ILI have been reported to DHMH. Of these, 32 (53%) have been outbreaks of ILI, and 28 (47%) have been outbreaks of lab-confirmed influenza.	Click on graph to enlarge
Influenza Hospitalizations Reported to DHMH – During week 18, NO hospitalizations due to influenza were reported to DHMH. To date, a total of 597 hospitalizations due to influenza have been reported to DHMH. Of these, 189 (32%) have been pediatric admissions, and 408 (68%) have been adults. To date, there has been ONE PEDIATRIC DEATH associated with influenza in a Maryland resident reported to DHMH.	Click on graph to enlarge
Download the weekly flu surveillance report