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 May 7, 2017 through May 13, 2017) in a printable format.


There were 6 cases of severe influenza (Philadelphia resident, positive by rapid test, PCR or culture, and hospitalized for = 24 hrs.) in Philadelphia during week19. Influenza A activity has reached baseline levels (data not shown). Influenza B activity declined again, and is approaching low, off season levels. Influenza-like illnesses (ILI) at emergency departments and pediatric ambulatory clinics remained at low levels for week 19. There have been a total of 30 outbreaks (= 1 case of laboratory confirmed influenza) in long-term care facilities for the 2016-2017 season. Twenty-one influenza-associated deaths have been reported for the season. No pediatric influenza-associated deaths have been reported.

Summary Table of Influenza and Influenza-like Illness Activity for Philadelphia

Surveillance Type Compared to Week of 04/30-05/06 Compared to 3 Year Seasonal* Mean
Hosp. ED Fever/flu visits -
Peds. Clinic ILI
Laboratory Influenza Surveillance
= Above 10% of comparison group
- = Equivalent to comparison group (-10% to +10%)
= Below 10% of comparison group
N/R = Data Not Reported

Philadelphia Hospitalized Influenza Cases By Age Group
October 1, 2016 - May 13, 2017

Philadelphia Hospital Influenza Cases by Age Group

Laboratory-based Surveillance for Influenza A: Philadelphia, 2013/2014 through 2016/2017 Seasons
Influenza-like illness at Philadelphia Emergency Departments and Pediatric Ambulatory Clinics, 2016-2017


Flu activity has peaked and continues to decline for week 19. The flu activity code is “sporadic.” Flu activity was low in all regions of the state. From 10/02/16 to 5/13/17, there were 70,447 flu cases (positive by rapid test, PCR, or culture). There were 50,508 (71.7%) Influenza A cases,19,693 (28.0%) Influenza B cases and 246 (0.3%) unknown cases. 585 cases made up the season-to-date influenza sub-typing results from state public health labs. Influenza A/H3 made up 83.4% of the positive cases followed by Influenza B/Victoria (7.5%), Other (5.0%) and Influenza B (4.1%). One influenza-associated death was reported this week. The influenza-associated death count is 145 for the 2016-2017 flu season, including four pediatric influenza-associated deaths.

United States

Flu activity decreased in the U.S. during week 19. The percentage of respiratory specimens that tested positive for influenza in clinical laboratories decreased. 9,528 specimens were tested at clinical laboratories and 415 (4.4%) specimens tested positive for influenza. 103 (24.8%) specimens tested positive for Influenza A and 312 (75.2%) specimens tested positive for Influenza B. 292 specimens were tested at public health labs and 81 (27.7%) specimens tested positive. Influenza B was the most frequently identified influenza virus that was reported by public health labs. The majority of recently circulating influenza viruses are susceptible to oseltamivir, zanamivir and peramivir. Although, rare sporadic instances of oseltamivir-resistant and peramivir-resistant influenza A (H1N1)pdm09 viruses and oseltamivir-resistant influenza A (H3N2) viruses have been detected worldwide. The proportion of deaths due to pneumonia and influenza was below the system-specific epidemic threshold for the National Center for Health Statistics Mortality Surveillance System. One influenza-associated pediatric death was reported to the CDC during week 19, bringing the total count to 92 for the 2016-2017 flu season. Between 10/01/16 and 5/13/17, a cumulative rate of 64.7 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported. The proportion of people visiting their health care provider for ILI was 1.3%, which is below the national baseline of 2.2%. Arizona experienced low ILI activity. Forty-seven states, including Delaware, New Jersey and Pennsylvania experienced minimal ILI activity. Five states reported that the geographic spread of influenza was regional. New Jersey and seven other states reported local influenza activity. Thirty-six states, including Delaware and Pennsylvania, reported sporadic influenza activity. Kansas reported no influenza activity.

Updated: 05/19/2017