2019/2020 Influenza Season Data
The Pennsylvania Department of Health monitors influenza 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 2019-2020 season, the influenza surveillance season began on Sept. 29, 2019, and will run through May 16, 2020. Updated influenza activity data will be posted on this web page every Tuesday throughout the influenza surveillance season. These updates will provide a summary on:
- When and where influenza activity is occurring;
- Current trends in influenza as compared to previous seasons; and
- 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.
Flu Activity Code: WIDESPREAD (week 12 ending 3/21/2020)
*The flu activity code is a characterization of the geographic spread of influenza in Pennsylvania. It does not indicate how severe the influenza season is. Rather, it indicates how much of Pennsylvania is experiencing influenza activity. The level of activity is classified based on CDC definitions below, which are used by all 50 states to characterize influenza activity.
No Activity|| No laboratory-confirmed cases of influenza and no reported increase in the number of cases of ILI.|
SPORADIC|| Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI|
LOCAL|| Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state|
REGIONAL|| Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state, with recent laboratory evidence of influenza in those regions|
WIDESPREAD || Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state, with recent laboratory evidence of influenza in the state|
Influenza surveillance data presented below reflect influenza activity during the time period referred to above. Data may change from week to week as numbers are adjusted for late reporting, misclassification of cases, and errors in classifying county or state of residence.
Pennsylvania Weekly Influenza Report
- Flu activity has decreased over the past few weeks but is still high.
- Percent outpatient visits related to influenza like illness has increased over past few weeks in outpatient clinics and emergency departments.
- The code for the geographic spread is ‘WIDESPREAD’ for week 12 that ended on 3/21/2020, which is the highest on a scale of five geographic spread levels
influenza A(H1N1) pdm09 is the most detected flu virus, however Influenza B/Victoria, and A(H3N2) viruses cocirculate in the community. The predominant viruses vary by region of the state and age group
- A total of 128,736 laboratory-confirmed influenza cases have been reported season to date. Confirmed reports were received from 67 Counties out of the 67 Counties.
- A total of 3,153 flu associated hospitalizations and 100 flu associated deaths have been reported season-to-date, including one pediatric influenza associated mortality.
Confirmed Influenza Laboratory Tests Received by PA DOH Surveillance
Table 1. Influenza Cases (positive by rapid test, PCR, or culture) Reported in Pennsylvania, 9/29/2019 to 3/21/2020 (n=128,736) - Cases by County and Influenza Type¥
|County||Influenza Type ||TOTAL|
|County Not Reported||174||173||4||351|
(*) 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 (n=422)
Table 2: Season-To-Date Influenza-Associated Deaths by Age
Influenza-associated Death |
65 + ||68|
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