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 Feb. 10, 2019 through Feb. 16, 2019) in a printable format.


Febrile/flu-like illnesses increased slightly among adults, while declining slightly for children and adolescents. The number of influenza positive specimens reported from our sentinel hospital laboratory surveillance network increased as well, with 23% of all respiratory specimens being positive for influenza. All but one of the positive specimens were influenza A. There were 24 reports of severe influenza (Philadelphia resident, positive by rapid test, PCR or culture, and hospitalized for = 24 hrs.) during this time frame, all of which were due to influenza A. Thirteen influenza-associated deaths have been reported so far this season, one during week 07. There was one influenza outbreak (= 1 case of laboratory confirmed influenza) reported in a long term care facility during week 07.

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 “widespread” influenza activity, which is defined by CDC as outbreaks of influenza or increases in influenza-like-illness and recent laboratory confirmed influenza in at least half the regions in the state. According to PADOH, influenza activity has increased during the past week in all state regions with the highest influenza activity reported in the northwest and southeast regions. From 9/30/18 to 2/16/19, there have been 37,808 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 (36,654 reports, 96.9%). Forty-seven influenza-associated deaths have been reported so far this season, including one pediatric death.

United States

Influenza activity continued to increase throughout the U.S. during week 07. Widespread influenza activity was reported by 48 states and Puerto Rico, while regional activity was reported by one state. Local activity was reported by DC and sporadic activity was reported by one state and the US Virgin Islands. The percentage of respiratory specimens that tested positive for influenza increased for reporting U.S. clinical laboratories. Specifically, 38,208 specimens were tested at US clinical laboratories, and 10,210 (26.7%) specimens tested positive for influenza. Of those positive, 9,936 (97.3%) specimens tested positive for influenza A and 274 (2.7%) specimens tested positive for influenza B. Among the 1,075 positive influenza specimens received by public health laboratories for confirmatory testing and subtyping during this week, 1,058 (98.4%) were influenza A and 17 (1.6%) were influenza B. Of the 996 influenza A specimens subtyped, 529 (53.1%) were subtyped as A(H1N1)pmd09 and 467 (46.9%) were subtyped as A/H3N2. Since September 30, 2018, CDC has antigenically characterized 1,129 influenza viruses [626 influenza A(H1N1)pdm09, 381 influenza A(H3N2), and 122 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 some 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. Sporadic instances of oseltamivir resistant and peramivir resistant influenza A(H1N1)pdm09 has been identified. Forty-one influenza-associated pediatric deaths have been identified nationally this season, seven during week 07.

Updated: 02/22/2019