Influenza: City flu vs. Country flu?

A recent news article reveled that my hometown, Butler County (PA), has the 3rd highest number of reported flu cases in the state with 121 reported cases.

I find that surprising given that our population is no where near the top of the list of the 67 counties that comprise Pennsylvania.

I don't think Butler County can have more influenza cases than Philadelphia County.

A couple of factors may be responsible for this disproportionate ranking:

  • Many hospitals, given flu activity is widespread, may be making clinical diagnoses of influenza rather than running diagnostic tests
  • The rapid influenza antigen test, which is used in many smaller hospitals (including in Butler), detects about a half of flu cases

In general, influenza diagnostics are very limited because of the unreliability of rapid antigen tests coupled with the fact that influenza PCR is done at few institutions and, when available, has a long turn-around-time.

However, I do recommend people avail themselves of whatever influenza diagnostics they have available in order to have some estimate available of influenza spread, alert infection control regarding hospitalized influenza patients, and to emphasize the need for antiviral treatment--which should not be withheld based on a negative rapid antigen test.