Flu cases in Arizona continue to rise

The Arizona Department of Health Services (ADHS) has released updated information about influenza activity in Arizona. According the ADHS, Arizona is in week 6 of the flu season.

Influenza activity highlights:

  • The numbers in this report are based on processed cases. There are a large number of reports that are still being processed.
  • 968 laboratory-confirmed cases of influenza were reported in the past week, from 15 counties. 22,917 cases have been reported this season, with laboratory-confirmed cases identified in 15 counties.
  • 19,807 (86%) reports this season are influenza A, 2,846 (12%) are influenza B, and 264 (2%) are of unknown type.
  • New data from the death certificate database were not available. To date, 461 pneumonia and influenza deaths were identified this season.
  • Two influenza-associated pediatric deaths have been reported for the 2017–2018 season in Maricopa County residents. One case was PCR positive for influenza A (H3), and one for influenza B/Victoria.

Laboratory-Confirmed Influenza Activity by Season

This past week there were 968 laboratory confirmed cases, over 100 more cases compared to the same week last season. There have been a total of over 19,500 more cases to date this season compared to last season.

15 counties had a laboratory confirmed case in the past three weeks

The age groups most affected by influenza vary somewhat season-to-season, depending in part on the circulating influenza types and subtypes and any existing immunity in the community. Variations in age groups of reported influenza cases can also be caused by differences in laboratory testing and reporting practices year-to-year.

A larger percentage of individuals 50 years and older are being affected by influenza this 2017–2018 season compared to the average of the five previous seasons.

Influenza types and subtypes

There are two main types of influenza – Type A and Type B – that cause illness in people. Influenza A viruses can be further divided into subtypes such as A (H1), or A (H3). While most tests can distinguish between influenza A and B, only specialized testing such as that done at the State Public Health Laboratory and a few other labs around the state can differentiate subtypes. Viral culture or molecular testing (reverse transcriptase polymerase chain reaction or RT-PCR) are the methods used to identify subtypes; knowing the type and subtype of the influenza viruses circulating can help health professionals make the best treatment and vaccination decisions.