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 5, 2019 through May 11, 2019) in a printable format.


Febrile/flu-like illnesses decreased among adults and people ages 5-17 years, but increased among children ages 0– 4 years. The number of influenza positive specimens reported from our sentinel hospital laboratory surveillance network remained extremely low, as only 1 specimen was positive for flu A and no specimens were positive for flu B. There were 2 reports of severe influenza (Philadelphia resident, positive by rapid test, PCR or culture, and hospitalized for = 24 hrs.) during this time frame, both of which were 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 19.

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 19. 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 four states, while local activity was reported by 16 states. Sporadic activity was reported by 28 states, D.C, and the U.S. Virgin Islands. No influenza activity was reported by two states. The percentage of respiratory specimens that tested positive for influenza decreased for reporting U.S. clinical laboratories. Specifically, 13,661 specimens were tested at US clinical laboratories and 506 (3.7%) specimens tested positive for influenza. Of those positive, 308 (60.9%) specimens tested positive for influenza A and 198 (39.1%) specimens tested positive for influenza B. Among the 51 positive influenza specimens received by public health laboratories for confirmatory testing and subtyping during this week, 35 (68.6%) were influenza A and 16 (31.4%) were influenza B. Of the 32 influenza A specimens subtyped, 14 (43.8%) were subtyped as A(H1N1)pmd09 and 18 (56.3%) were subtyped as A/H3N2. Since September 30, 2018, CDC has antigenically characterized 2,612 influenza viruses [1,199 influenza A(H1N1)pdm09, 984 influenza A(H3N2), and 429 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 nine influenza-associated pediatric deaths have been identified nationally this season, three during week 19.

Updated: 05/17/2019