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 December 31, 2017 through January 6, 2018) in a printable format.


Febrile/flu-like illnesses at emergency departments increased for adults (18 years and older) while activity declined for children and adolescents. Sentinel hospital laboratory surveillance for influenza A or B continued to detect increases among respiratory specimens for both types. There were 41 reports of severe influenza (Philadelphia resident, positive by rapid test, PCR or culture, and hospitalized for = 24 hrs.) during this time frame, of which 34 (82.9%) of hospitalizations were due to influenza A. Two influenza-associated deaths were reported so far this season. There was 1 influenza outbreak (= 1 case of laboratory confirmed influenza case) reported in a long term care facility for week 01.

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, the southeast region is experiencing the greatest amount of influenza activity. From 10/1/17 to 1/6/18, there have been 11,530 reports of influenza (positive by rapid test, PCR, or culture). The majority of influenza throughout the state has been identified as influenza A (10,054 reports, 87.2%). There have been 18 influenza related deaths have been reported this season, including one pediatric death, with 12 deaths occurring during week 1.

United States

Influenza activity continued to increase throughout the U.S. during week 01. Widespread transmission was reported in 49 states, while 1 state and Guam reported regional activity. Local activity was reported by the District of Columbia. The percentage of respiratory specimens that tested positive for influenza remained constant during week 01. Specifically, 41,712 specimens were tested at US clinical laboratories, and 10,320 (24.7%) specimens tested positive for influenza. Of those positive, 8,628 (83.6%) specimens tested positive for influenza A and 1,692 (16.4%) specimens tested positive for influenza B. Among the 1,398 positive influenza specimens received by public health laboratories for confirmatory testing and subtyping, 1,202 (86%) were influenza A and 196 (14%) were influenza B. Of the influenza A specimens, 1,021 (84.9%) were subtyped as H3N2. During October 1, 2017-January 6, 2018, CDC has antigenically or genetically characterized 836 influenza viruses [138 influenza A(H1N1)pdm09, 474 influenza A(H3N2), and 224 influenza B viruses] collected by U.S. laboratories. The majority of influenza viruses collected were characterized antigenically and genetically as being similar to the cell-grown reference viruses representing the 2017-2018 Northern Hemisphere influenza vaccine viruses. Among 164 Influenza A(H1N1)pdm09 samples tested for resistance to neuraminidase inhibitors, 2 (1.2%) were resistant to oseltamivir and 2(1.2%) 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 20 influenza-associated pediatric deaths have been identified nationally this season, 7 during week 01. 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: 01/12/2018