Influenza Surveillance Archive

Monitoring Activities

Cases of ILI (fever >100 and cough or sore throat) are reported to the SNHD. The number of patients seen for any reason is also reported to the Health District so that the percentage of patients seen for ILI by age can be calculated.

The percentage of patients with ILI by age is analyzed weekly to determine whether there are increases in the occurrence of ILI and if there are changes in the distribution by age.

Since reports of ILI are based on clinical impression, it is important to determine whether there are cases of influenza in the community that have been confirmed by laboratory tests. A limited number of nasopharyngeal swabs are obtained on patients presenting with the above symptoms within 48 hours of symptom onset.

Cultures that are positive for influenza A or B are submitted to Nevada State Health Laboratory for subtyping. As noted above this information is needed to determine whether the current vaccine is effective against the influenza virus currently circulating and also to plan for the next year’s vaccine.

Results of information from clinical and laboratory reports are disseminated on a weekly basis to the participating sentinel sites, the Nevada State Health Division and to the Centers for Disease Control.

Influenza Vaccine Information

The vaccine strains chosen for the 2007-2008 season include A/Solomon Islands/3/2006 (H1N1)-like, an A/Wisconsin/67/2005 (H3N2)-like virus and a B/Malaysia/2506/2004-like virus; however, manufactures may substitute A/Wisconsin/67/2005 with A/Hiroshima/52/2005 and B/Malaysia/2506/2004 for B/Ohio/1/2005. These strains were chosen because they are predicted to be representative of the 2007-2008 influenza season and have favorable growth in eggs.

The influenza vaccine is generally safe. Persons with severe allergic reactions to eggs should not receive influenza vaccine, since the vaccine is prepared from influenza viruses grown in eggs. The most common side effect is mild soreness at the injection site. Serious side effects such as life-threatening allergic reactions or Guillain-Barre syndrome are rare (fewer than 1-2 cases per million vaccine recipients); however persons with a past history of Guillain-Barre syndrome or with allergy to thimerosal (a preservative) should not receive the vaccine. Anyone currently ill with fever >101°F should delay immunization.

The SNHD administers the inactivated influenza vaccination at a cost of $30.00 per person. For further information regarding influenza vaccine, please visit our Flu Vaccine webpage or call our Immunization Program at (702) 759-0850.

2006-2007 Clark County Statistics

It is important to note that cases reported as ILI may not actually have influenza since the diagnosis is made by a health professional based on symptoms and is not dependent on laboratory tests. Symptoms of ILI, (fever > 100°F and a cough or sore throat), may also be present in persons presenting with other respiratory illnesses such as parainfluenza infections, respiratory synctial virus or adenovirus infections. Laboratory tests for confirmation of influenza are requested infrequently.

The figure below shows the percentage of ILI cases of all patients seen at participating sites for any reason in Clark County for the 2006-2007 surveillance season.