The Philadelphia Department of Public Health (PDPH) Division of Disease Control conducts weekly influenza surveillance using chief complaints from Emergency Departments, influenza-like illness visit data, laboratory-based surveillance and institutional surveillance during flu season. The results of this surveillance are posted here every Friday in the season.

Click here for more information on Influenza, including how and when to report a case and other disease guidance.

Click here to download the 2017-2018 influenza season summary report in a printable format.

Click here to download the last weekly report of influenza activity (from May 12, 2019 through May 19, 2019) in a printable format.


Febrile/flu-like illnesses increased slightly across all age groups. The number of influenza positive specimens reported from our sentinel hospital laboratory surveillance network remained low, as only 3 specimen was positive for flu A and one specimen was positive for flu B. There was 1 report of severe influenza (Philadelphia resident, positive by rapid test, PCR or culture, and hospitalized for = 24 hrs.) during this time frame, a hospitalization due to influenza A. Twenty-nine influenza-associated deaths have been reported so far this season. There were no influenza outbreaks (= 1 case of laboratory confirmed influenza) reported in a long term care facility during week 20.

Febrile/Flu-like Illnesses at Philadelphia Emergency Departments 2017-2018 Data Compared to 4 Year Historical Weekly Averages Laboratory-based Surveillance for Influenza A: Philadelphia, 2013/2014 through 2017/2018 Seasons

Laboratory-based Surveillance for Influenza A: Philadelphia, 2013/2014 through 2017/2018 Seasons


The Pennsylvania Department of Health (PADOH) has reported “local” influenza activity, which is defined by CDC as outbreaks of influenza or increases in influenza-like-illness and recent laboratory confirmed influenza in a single region of the state. According to PADOH, influenza activity has continued to decrease during the past week in all state regions and is below the epidemic threshold. The highest influenza activity was reported in the northeast region. From 9/30/18 to 5/11/19, there have been 98,453 laboratory confirmed cases of influenza (positive by rapid test, PCR, or culture). The majority of influenza throughout the state has been identified as influenza A (94,059 reports, 95.5%). One hundred fifty-seven influenza-associated deaths have been reported so far this season, including two pediatric deaths.

United States

Influenza activity continued to decrease in the U.S. during week 20. Influenza A(H1N1)pdm09 viruses predominated from October to mid-February and Influenza A(H3N2) viruses have been more commonly identified since late February. Small numbers of influenza B viruses have also been reported. Regional activity was reported by Puerto Rico and Arizona, while local activity was reported by 8 states. Sporadic activity was reported by 36 states, D.C, and the U.S. Virgin Islands. No influenza activity was reported by four states. The percentage of respiratory specimens that tested positive for influenza decreased for reporting U.S. clinical laboratories. Specifically, 12,244 specimens were tested at US clinical laboratories and 470 (3.7%) specimens tested positive for influenza. Of those positive, 260 (55.3%) specimens tested positive for influenza A and 210 (44.7%) specimens tested positive for influenza B. Among the 42 positive influenza specimens received by public health laboratories for confirmatory testing and subtyping during week 20, 27 (64.3%) were influenza A and 15 (35.7%) were influenza B. Of the 27 influenza A specimens subtyped, 6 (23.1%) were subtyped as A(H1N1)pmd09 and 20 (76.9%) were subtyped as A/H3N2. Since September 30, 2018, CDC has antigenically characterized 2,637 influenza viruses [1,207 influenza A(H1N1)pdm09, 990 influenza A(H3N2), and 440 influenza B viruses] collected by U.S. laboratories. The majority of influenza A viruses collected were antigenically similar to the cell-grown reference viruses representing the 2018-2019 Northern Hemisphere influenza vaccine viruses, although genetic diversity exists for the H3N2 viruses. Of the influenza B lineages, all of the Yamagata lineage viruses matched the vaccine strain however, antigenically distinct subclades have emerged for the Victoria lineage. The majority of influenza viruses tested show susceptibility to oseltamivir and peramivir. All influenza viruses showed susceptibility to zanamirvir. One hundred eleven influenza-associated pediatric deaths have been identified nationally this season, two during week 20.

Updated: 06/26/2019