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 April 16, 2017 through April 22, 2017) in a printable format.


There were 28 cases of severe influenza (Philadelphia resident, positive by rapid test, PCR or culture, and hospitalized for = 24 hrs.) in Philadelphia during week16. Influenza A activity has reached baseline levels (data not shown). Influenza B activity has declined for the past two weeks. Influenza-like illnesses (ILI) at emergency departments and pediatric ambulatory clinics also declined for week 16. There have been a total of 30 outbreaks (= 1 case of laboratory confirmed influenza) in long-term care facilities for the 2016-2017 season. Seventeen 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 04/09-04/15 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 - April 22, 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 16. The flu activity code is “regional.” The highest flu activity was reported in the southeast region of the state. From 10/02/16 to 4/22/17, there were 69,249 flu cases (positive by rapid test, PCR, or culture). There were 50,247 (72.6%) Influenza A cases,18,759 (27.1%) Influenza B cases and 243 (0.4%) unknown cases. 571 cases made up the season-to-date influenza sub-typing results from state public health labs. Influenza A/H3 made up 85.5% of the positive cases followed by Influenza B/Victoria (6.1%), Influenza B (4.7%),and other (7.9%). Four influenza-associated deaths were reported this week bringing the total count to 141 for the 2016-2017 flu season, including three pediatric influenza-associated deaths.

United States

Flu activity decreased in the U.S. during week 16. The percentage of respiratory specimens that tested positive for influenza in clinical laboratories decreased. 14,889 specimens were tested at clinical laboratories and 1,426 (9.6%) specimens tested positive for influenza. 366 (25.7%) specimens tested positive for Influenza A and 1,060 (74.3%) specimens tested positive for Influenza B. 597 specimens were tested at public health labs and 215 (36.0%) 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. Six influenza-associated pediatric deaths were reported to CDC during week 15, bringing the total count to 83 for the 2016-2017 flu season. Between 10/01/16 and 4/22/17, a cumulative rate of 62.7 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported. The proportion of people visiting their health care provider for influenza-like illness (ILI) was 1.8%, which is below the national baseline of 2.2%. Four states experienced low ILI activity. Delaware, New Jersey, Pennsylvania and 43 states experienced minimal ILI activity. Seven states, including Delaware, reported that the geographic spread of influenza was widespread. New Jersey, Pennsylvania and 9 other states reported regional influenza activity. Washington, DC and 19 states reported local influenza activity. Thirteen states reported sporadic activity.

Updated: 04/28/2017