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2020/2021 Influenza Season Data

The Pennsylvania Department of Health monitors influenza activity, conducts laboratory testing and compiles reports on flu activity throughout the year but ramps up surveillance activities in the fall and winter. The official influenza surveillance season starts with the 40th week of the year (typically around the beginning of October) and ends on the 20th week of the following year (in May). For the 2020-2021 season, the influenza surveillance season will begin on Sept. 27, 2020, and will run through May 22, 2021. The department will stop updating this page as flu activity is very low at this time and will resume the updates in the beginning of the 2021-2022 flu season. The below final update from May 25, 2021 provided a summary on:

  1. When and where influenza activity is occurring;
  2. Current trends in influenza as compared to previous seasons; and
  3. What types and subtypes of influenza viruses are currently circulating. 

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 20 (Ending 5/22/2021)

Pennsylvania Weekly Influenza Report
Summary:

  • Flu activity was unusually low across the Commonwealth and nationally during this season. 
  • Influenza A and B are identified by laboratory testing.
  • A total of 3,664 laboratory-confirmed influenza cases have been reported season to date, this is 95% decrease from cumulative count of cases during the same week of the 2019-2020 flu season. Confirmed reports were received from 67 Counties of the 67 Counties.
  • Percent of outpatient visits associated with Influenza-Like Illness (ILI) has been low and is still below the state epidemic threshold however, the activity has increased slightly over the past few weeks.
  • A total of 45 influenza associated hospitalizations and 21 deaths have been reported in Pa during the current flu season.

Confirmed Influenza Laboratory Tests Received by PA DOH Surveillance

Table 1. Influenza Cases (positive by rapid test, PCR, or culture) Reported in Pennsylvania, 9/27/2020 to 5/22/2021 (n=3,664) - Cases by County and Influenza Type¥  

The numbers per county did not increase to a level that protects the confidentiality of the patients' health information, so the data will not be posted this season.

CountyInfluenza Type ​ ​TOTAL
ABU
County Not Reported    
ADAMS    
ALLEGHENY    
ARMSTRONG    
BEAVER    
BEDFORD    
BERKS    
BLAIR    
BRADFORD    
BUCKS    
BUTLER    
CAMBRIA    
CAMERON    
CARBON    
CENTRE    
CHESTER    
CLARION    
CLEARFIELD    
CLINTON    
COLUMBIA    
CRAWFORD    
CUMBERLAND    
DAUPHIN    
DELAWARE    
ELK    
ERIE    
FAYETTE    
FOREST    
FRANKLIN    
FULTON    
GREENE    
HUNTINGDON    
INDIANA    
JEFFERSON    
JUNIATA    
LACKAWANNA    
LANCASTER    
LAWRENCE    
LEBANON    
LEHIGH    
LUZERNE    
LYCOMING    
MCKEAN    
MERCER    
MIFFLIN    
MONROE    
MONTGOMERY    
MONTOUR    
NORTHAMPTON    
NORTHUMBERLAND    
PERRY    
PHILADELPHIA    
PIKE    
POTTER    
SCHUYLKILL    
SNYDER    
SOMERSET    
SULLIVAN    
SUSQUEHANNA    
TIOGA    
UNION    
VENANGO    
WARREN    
WASHINGTON    
WAYNE    
WESTMORELAND    
WYOMING    
YORK    
All    

(*) 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 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 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

The chart will be created when enough data are collected.

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

Age Influenza-associated Death
0-18 0
19-49 2
50-64 6
65 + 13
All 21

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 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 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

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

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