Mono-Gram - Influenza Season Winding Down 4/8/15

Influenza Season Winding Down

The masking period for Mono County healthcare workers who did not receive an influenza vaccination has now ended. However, influenza continues to circulate at low levels.

Throughout the year, public health conducts screening of all Sierra Park Family Medicine and Pediatrics visits for influenza-like illness (ILI), which is defined as a documented (by history or exam) fever of >=100 degrees F, accompanied by a cough and/or sore throat, not explained by another diagnosis (e.g., strept throat or RSV).

The accompanying chart shows that ILI visits to Sierra Park Family Medicine have a baseline of <1%, with Pediatrics at about 2%. We saw our uptick during Christmas week, largely in the visitor population. Once they left, it took another few weeks for our locals to show a peak of illness. This happened in January, about a month before the usual peak in February. Last week was the first week that we are back to near baseline levels.

Early in the season it was a type A H3N2 strain that predominated. About 75% of the H3N2 viruses that were circulating had drifted from the strain in the vaccine. Evidence showed poor coverage in the vaccine for this strain, which is particularly hard on the very young and very old. Our experience mirrors this, as virtually all of our hospitalizations at Mammoth Hospital for influenza and/or pneumonia were in the very young or the very old. The hospitalization rate nationwide for the >65 year old age group was the highest recorded since this type of record keeping began in 2005.

So far this season in the US, there have been 116 pediatric deaths reported (less than age 18 years). The range since 2004 has been from 37 to 171 pediatric deaths. The importance of vaccination, including vaccination of adults who are around children, is emphasized by these two very concerning facts:

  • 46% had no recognized underlying health problems
  • 80% of pediatric deaths occurred in unvaccinated children

The usual flu season is 13 weeks in length. This year, having started and peaked relatively early, it is expected to last longer. If current trends continue, our flu season in Mammoth will have been 15 weeks long. Statewide, influenza B has been the predominant strain since the beginning of March. This is typical for the end of the flu season. The strains circulating are covered by the vaccine.

The strains in next years’ vaccine have been selected, and production is underway. We will work with you in doing everything we can to protect ourselves, our families, our patients, and our community.