Steve Halasey, CLP.

Steve Halasey, CLP.

According to the US Centers for Disease Control and Prevention (CDC), the exact timing and duration of the northern hemisphere’s flu season varies every year, but usually peaks between December and February.

CDC should know. For more than 30 years, the agency has been collecting, compiling, and analyzing information about influenza activity in the United States, and now produces a weekly report about flu outbreaks throughout the extended period of flu activity from October through mid-May. To gather the information necessary for such tracking, CDC relies on the US influenza surveillance system, a collaborative effort involving CDC and many partners in state and local health departments, public health and clinical laboratories, vital statistics offices, physicians, clinics, and emergency departments.

CDC’s flu surveillance system collects information in five categories: virologic surveillance (including surveillance for novel influenza viruses), outpatient illness, mortality, hospitalization, and geographic spread. Taken together, the reports of the surveillance network enable CDC to:

  • Find out when and where influenza activity is occurring.
  • Track influenza-related illness.
  • Determine what influenza viruses are circulating.
  • Detect changes in influenza viruses.
  • Measure the impact influenza is having on hospitalizations and deaths in the United States.

According to the agency, such a comprehensive and timely overview of influenza activity is an essential public health activity for a variety of reasons. Influenza viruses are constantly changing—sometimes very rapidly—so ongoing data collection and characterization of the strains is essential for preventing flu pandemics. National responses to emerging pandemic strains are triggered by surveillance data.

Moreover, treatment of individual patients for influenza is also guided by laboratory surveillance. Varying segments of the population are affected by influenza and may require targeted interventions. To keep up with changes in the flu virus in circulation, vaccines must be administered annually and are updated regularly based on surveillance findings of antiviral resistance. (For more information on current testing methodologies for influenza, access CLP’s free webcast “Influenza Testing Today: Keeping Up with a Moving Target.”) 

Through the end of October, CDC has reported that overall seasonal flu activity is low in all regions of the United States. The proportion of people visiting their healthcare providers for influenza-like illness is 1.4%, which is below the national baseline of 2.1% for this time of year. Of the 29 influenza-positive tests reported to CDC by public health laboratories, 23 were influenza A viruses (with H3 strains predominating), and six were influenza viruses.

How can CDC’s information be so precise and timely? Take a look at the two articles on flu and respiratory virus diagnostics in this issue of CLP, and you’ll get a pretty good idea of the originating source for all of this activity.

Without advanced flu diagnostics and the clinical laboratories that perform flu testing, we would all know a lot less about this major threat to public and individual health. And such a lack of information could turn even a slow-starting and mild flu season into a big problem.

Now, I’m off to get my flu shot for the year. How about you?

Steve Halasey
Chief Editor, CLP
[email protected]
(626) 219-0199