Influenza Season Update

As most of you know, this is a banner influenza year. We are seeing a lot of influenza activity in all communities and two interesting things are worth taking note of. First, we are seeing more influenza B than usual. Our influenza B rates are running up to 50% of all influenza isolates (usually we see closer to 25-30%) and perhaps more importantly we are seeing a mismatch between the strains in the vaccine and the strains circulating in the community. The CDC is estimating that 57% of circulating strains are mismatched. These are: A/Brisbane/10/2007-like which is an antigenically distinct variant of the A/Wisconsin/67/2005-like, the H3 component of the 2007-8 vaccine, and B/Ohio/01/2005-like, ann antigenically distinct variant of the B/Malaysia/2506/2004-like , the influenza B component of the 2007-2008 vaccine. We will know more as the season comes to a close, but for now influenza is still going strong. Hospitalization rates for children are tracked by the CDC and appear to be similiar to previous years. All of this information and more is available on the CDC website (http://www.cdc.gov/flu/weekly/fluactivity.htm) as well as the local LA County Health Department website (http://lapublichealth.org/acd/Flu_Sea_Surveillance.htm).

High Influenza Activity in Southern California

We continue to have very high numbers of positive influenza tests. In contrast to previous years, and as mentioned previously, we are seeing more influenza B than usual. Early indicators from the CDC report that there may be a mismatch of both influenza B and influenza A (H3) strains, but interpret these cautiously as this is based on a small number of early isolates. I would also like to provide you with a link to the LA County surveillance link and will place this a permanent link on our website.
This is a terrific site that tracks influenza and influenza like illnesses and hospital admissions in LA County. It is a wonderful complement to our raw data site! The link can be accessed at:

http://lapublichealth.org/acd/Flu_Sea_Surveillance.htm