Influenza Surveillance - South Dakota Health Department

South Dakota Surveillance

Surveillance summaries are posted weekly at this site during the flu season.

Information from CDC's 2/8/2008 Press Conference
on Vaccine Effectiveness and Tamiflu resistance

84% of all the viruses that have been typed have been Influenza A
More than half have been H1N1, 96% of these match the strain in the 07/08 Influenza vaccine
Less than half have been H3N2, 87% of these do not match the strain in the 07/08 Influenza vaccine
16% of all the viruses that have been typed have been Influenza B, 93% are of a lineage that does not match the 07/08 Influenza vaccine.
While a less than ideal virus match between viruses in the vaccine and those circulating in the community can reduce vaccine effectiveness, we know from past influenza studies that the vaccine can still protect enough to make illness milder or prevent flu-related complications.
4.5% of the influenza viruses have been shown to be resistant to Tamiflu.
All of the resistant viruses are among the subtype A (H1N1) and if you just look at that subtype, 8.1% are resistant to Tamiflu.
There has not been any resistance yet among the A (H3N2) viruses or among the B viruses tested this year.

The CDC & South Dakota Department of Health recommend people take the following steps to protect against influenza.

Get a flu shot. Vaccination now can still provide protection against influenza this season since different influenza viruses can circulate as late as May. Vaccine is still available – contact the Department of Health or your local clinic.
Practice the common sense hygiene measures of the department’s “Stop It, Don’t Spread It” campaign – wash your hands often, cover coughs and sneezes to keep germs from spreading and stay home when sick.
Take antiviral drugs if your doctor says to. Antiviral drugs are an important second line of defense against influenza and they can be used to treat or prevent influenza virus infection.

National Surveillance Information

During week 14 (March 30 – April 5, 2008), influenza activity continued to decrease in the United States. The proportion of deaths attributed to pneumonia and influenza has been above the epidemic threshold for 13 consecutive weeks. The proportion of outpatient visits for influenza-like illness (ILI) and the proportion of outpatient visits for acute respiratory illness (ARI) were below national baseline levels. ILI decreased in all nine regions compared to week 13, but remained above the region-specific baselines in the East North Central and West North Central regions. The proportion of outpatient visits reported for ARI was below all region and age-specific baselines. 6 states reported widespread influenza activity; 11 states reported regional influenza activity; 23 states reported local influenza activity; and 10 states reported sporadic influenza activity.
See the CDC website for weekly surveillance reports during influenza season.

Definitions

*SD reports influenza activity to the Centers for Disease Control and Prevention using the following CDC definitions.

Influenza-like illness	Fever >=100° F and cough or sore throat
No Activity	Overall clinical activity remains low and there are no lab confirmed cases
Sporadic Activity	Isolated cases of lab confirmed influenza in the state; Influenza-Like-Illness (ILI) activity is not increased.
Local Activity	Increased ILI within a single region** AND recent (within the past 3 weeks) laboratory evidence of influenza in that region. ILI activity in other regions is not increased.
Regional Activity	Increased ILI in ≥2 but less than half of the regions AND recent (within the past 3 weeks) lab confirmed influenza in the affected regions.
Widespread Activity	Increased ILI and/or institutional outbreaks (ILI or lab confirmed) in at least half of the regions AND recent (within the past 3 weeks) lab confirmed influenza in the state.