2022/2023 Influenza Season Data

Note: PA DOH continuously conducts flu surveillance throughout the year. Currently, flu activity is at interseasonal levels, which is relatively low. As a result, the flu activity report will be paused until the next flu season when flu activity is expected to increase.

It is important to note that the influenza case counts presented on this page are restricted to only those cases that have had a positive laboratory test for flu (by rapid test, DFA, PCR or culture) reported to the PADOH. These case counts represent only a fraction of the actual burden of illness due to influenza occurring in the commonwealth at any given time. This is because most persons with influenza do not go to the doctor or are not tested or reported. Influenza spread and severity varies widely from season to season. It is estimated that five to 20 percent (600,000 to 2,400,000) of Pennsylvanians get the flu each year, and 120 to 2,000 die from complications of influenza.

Week 17 (Ending 4/29/2023)

Pennsylvania Weekly Influenza Report Summary:

• Seasonal influenza activity in Pennsylvania and the United States is low.
• Influenza A and B are identified by laboratory testing. While the most frequently reported and subtyped influenza virus this season is A(H3N2), the predominant type in the past few weeks has been Influenza B.
• A total of 186,611 laboratory-confirmed influenza cases have been reported season to date. Confirmed reports were received from the 67 state counties.
  
• The percent of emergency department visits associated with influenza-like illness is low at this time.
  
• A total of 169 confirmed influenza-associated deaths have been reported during the current season.
  

Confirmed Influenza Laboratory Tests Received by PA DOH Surveillance

Table 1. Influenza Cases (positive by rapid test, PCR, or culture) Reported in Pennsylvania, 10/02/2022 to 4/29/2023 (n=186,611) - Cases by County and Influenza Type*¥

(*) Numbers smaller than 5 have been replaced with an asterisk

(¥) Influenza counts are provisional and may change as more information is received

(**) Test results may identify influenza Type A, influenza Type B, or influenza without specifying Type A or B. Some tests only give a positive or negative result and can-not identify influenza type.

Figure 1. Number of Pa. Influenza Cases by Week of First Report

Figure 2: Comparison of PA-NEDSS Influenza Cases (All Types) in Current Season to the Eight Previous Seasons

Figure 3: Season-to-date Influenza Sub-Typing Results From State Public Health Lab

Table 2: Season-To-Date Influenza-Associated Deaths by Age

Syndromic Surveillance

The Pennsylvania Department of Health's syndromic surveillance system receives data on visits to emergency departments (EDs) from most hospitals in the state.  The system looks at the reason for visiting the ED and determines if ED visits were likely due to influenza-like illness (ILI). The graph displays ED visits due to ILI as a percentage of total ED visits. This provides yet another way for the Department of Health to monitor influenza and ILI in the state. 

Figure 4: season-to-date Influenza-Like Illness (ILI) Emergency Visits

Figure 5: season-to-date Influenza-Like Illness (ILI) Emergency Visits by community health districts 

Figure 6: season-to-date Influenza-Like Illness (ILI) Emergency Visits by age groups

World Health Organization (WHO) and National Respiratory & Enteric Virus Surveillance System (NREVSS) Collaborating Laboratories

Thirteen clinical virology laboratories in Pa. are WHO and/or NREVSS collaborating laboratories for influenza surveillance.

These labs report weekly the number of respiratory specimens tested and the number positive for influenza types A and B to CDC. Some labs also report the influenza A subtype (H1 or H3) and influenza B lineage (Victoria or Yamagata). Because denominator data is provided, the weekly percentage of specimens testing positive for influenza is calculated.

Figure 7: Influenza Test Results Reported to the National Respiratory and Enteric Virus Surveillance System (NREVSS) Select Pennsylvania Laboratories, Season to date