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 last weekly report of influenza activity (from February 11, 2018 through February 17, 2018) in a printable format.


During week 7, febrile/flu-like illnesses at emergency departments increased for adults and for children < 5 years of age, while they remained level for children and adolescents ages 5-17 years. Sentinel hospital laboratory surveillance for influenza A and B detected increases among respiratory specimens for both influenza types. There were 140 reports of severe influenza (Philadelphia resident, positive by rapid test, PCR or culture, and hospitalized for = 24 hrs.) during this time frame, of which 91 (65%) of hospitalizations were due to influenza A. Twenty– one influenza-associated deaths were reported so far this season, one during week 07. There were 5 influenza outbreaks (= 1 case of laboratory confirmed influenza case) reported in a long term care facility for week 07.

Febrile/Flu-like Illinesses 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 influenza activity that is increasing in at least half the regions of the state. According to PADOH, although influenza activity is still widespread, it has decreased in all the state regions except the southeast region. From 10/1/17 to 2/17/18, there have been 74,247 reports of influenza (positive by rapid test, PCR, or culture). The majority of influenza throughout the state has been identified as influenza A (57,684 reports, 77.7%). There have been 135 influenza related deaths reported this season, including two pediatric deaths, with 28 deaths occurring during week 07.

United States

Influenza activity remained constant throughout the U.S. during week 07. Widespread activity was reported in 48 states and Puerto Rico, while 2 states (Hawaii and Oregon) , the District of Columbia, and Guam reported local activity. The percentage of respiratory specimens that tested positive for influenza decreased slightly during week 07. Specifically, 54,063 specimens were tested at US clinical laboratories, and 13,730 (25.4%) specimens tested positive for influenza. Of those positive, 7,987 (58.2%) specimens tested positive for influenza A and 5,743 (41.6%) specimens tested positive for influenza B. Among the 985 positive influenza specimens received by public health laboratories for confirmatory testing and subtyping, 636 (64.6%) were influenza A and 349 (35.4%) were influenza B. Of the influenza A specimens, 469 (73.7%) were subtyped as H3N2 and 143 (22.5%) were subtyped as A(H1N1)pmd09. During October 1, 2017-February 17, 2018, CDC has antigenically or genetically characterized 1,599 influenza viruses [350 influenza A(H1N1)pdm09, 779 influenza A(H3N2), and 470 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 2017-2018 Northern Hemisphere influenza vaccine viruses, although some genetic diversity exists for the H3N2 viruses. The majority of influenza B viruses were antigenically similar although a minority (41.1%) of the Influenza B Victoria viruses appear not to be similar. Among 467 Influenza A(H1N1)pdm09 samples tested for resistance to neuraminidase inhibitors, 4 (0.9%) were resistant to oseltamivir and 4(0.9%) were resistant to peramivir. No Influenza A(H1N1)pdm09 viruses were resistant to zanamivir. No Influenza A(H3N2) and Influenza B viruses were resistant to oseltamivir, zanamivir, and peramivir. A total of 97 influenza-associated pediatric deaths have been identified nationally this season, 13 during week 07. Two novel infections of influenza A (1 H3N2v and 1 H1N1v) were identified this season in persons who reported direct contact with swine. No human to human transmission has been identified.

Updated: 02/23/2018