1. Surveillance in a Pandemic: Situational Awareness
and Assessing Severity
Daniel B. Jernigan, MD MPH
Deputy Director, Influenza Division
National Center for Immunization and Respiratory Diseases 1

2. Objectives
Describe the US experience with surveillance and situational awareness during the 2009 pandemic
Identify some things that worked and some that could be improved
Describe the challenges of measuring severity in an emerging pandemic

3. First Cases Prompt Investigation
MMWR
First Cases Prompt Investigation
April 21 report of two cases in Southern California
Both cases seen as outpatients, both recovered
April 24 report of link with cases in Mexico
Same virus, different sense of “severity” or potential impact
Cases prompted a cascade of activity
Enhanced surveillance
Virus characterization

4. CDC Virologic Surveillance in the First Week
196,000
Specimens
Tested Over
the Season
35,000
Specimens
Tested in
One Week
2008
2009 4

5. Early Assessment April 28 May 1 Virus
CDC Posted PCR
Protocol on
WHO website
May 1
First Diagnostic Kits Shipped to
WHO Network and State Labs
To date: 2,125 kits to
432 labs in 142 Countries
Virus
Detected
Field Investigations and Enhanced Surveillance
April 27
CDC posts 40 gene sequences on GenBank
May 23
Vaccine Strain
Begins Shipping to
Manufacturers
May 7
Case Series (N=642) Published in NEJM

6. Early Estimate of Symptomatic Case Fatality Ratio Reed, Biggerstaff – CDC unpublished data

7. Making Situational Awareness Possible in the First Days
Early communication accelerated global response
Case-contact investigations and community surveys were critical for early characterization
Availability of diagnostics aided response
PCR devices in place or quickly deployed
Influenza Reagent Resource for distribution
Preparedness investments invaluable

8. Early Challenges Decisions need to be made on limited data
Estimating and monitoring impact is an ongoing process
Need to manage expectations of stakeholders and decision-makers
Pandemic planning called for severity estimates based on mortality alone; however,
may not be available
may not reflect the potential impact of the pandemic
are difficult to maintain with lab-confirmation

9. Pandemic Severity Index Benchmarked to Past Pandemic Mortality

10. During the Summer

11. CDC Virologic Surveillance During the Summer Months
ILI visits greatly increased above baseline
Notably in younger patients
Hospitalization rates point to increases in younger patients
PCR-confirmed case counting stopped
2008
2009 11

12. Situational Awareness from Campers A Personal Account
On Arrival at Camp
Cabin has 25 Campers

13. Situational Awareness from Campers A Personal Account
On Arrival at Camp
Cabin has 25 Campers
One Week Later
Cabin has 11 Campers

14. Observations from the Summer
Existing laboratory and epidemiologic infrastructure critical for sustained surge
New surveillance activities initiated
Aggregate hospitalization and deaths reporting
Reports from electronic health records
Serologic studies helpful for indicating immunity in older individuals
need more automated and rapid testing capacity
Uncertainty of potential changes in the virus required maintained vigilance and planning

15. Through the Fall Wave

16. CDC Virologic Surveillance through the Fall Wave
2008
2009 16

17. Death Hospital Clinics & ED’s
Assessing “severity” or “influenza impact” was accomplished using surveillance data
to monitor morbidity and mortality
to compare with prior seasons
to estimate numbers of cases
Death
Hospital
Clinics & ED’s

18. Visits for ILI surpassed prior seasons, notably among younger age groups
Schools
Start

19. 2009 H1N1 Hospitalizations varied by age and differed from previous seasons CDC Emerging Infections Program
* Pan H1N1 is for data from Sep 1, 2009 to Jan 21, 2010

20. Pneumonia and Influenza Mortality for 122 U. S
Pneumonia and Influenza Mortality for 122 U.S. Cities Aggregate data does not represent impact on those <65
H3N2
Fall
Wave

21. Number of Influenza-Associated Laboratory-Confirmed Pediatric Deaths
88 Pediatric Deaths
69 Pediatric Deaths 21

22. Number of Influenza-Associated Laboratory-Confirmed Pediatric Deaths
4 – 5 times more than
prior seasons
Since H1N1
344 Pediatric Deaths
88 Pediatric Deaths
69 Pediatric Deaths 22

23. Deaths Hospitalizations Cases
Characteristics of 2009 H1N1 Influenza April 15, 2009 to April 10, 2010
Deaths
12,470 (8.9K – 19.3K)
Hospitalizations
274,000 (195K – 403K)
Approximate Rate per 100,000 population
Cases
61,000,000 (43M – 89M)
0-4
5-24
25-49
50-64
≥65

24. Assessing Severity Assessments
Mortality alone does not reflect the full pandemic impact
90% of deaths generally among >65 yos
For H1N1, 90% among <65 yos
Lab-confirmed cases underreported
Estimates of years of potential life lost range 334K to 1.2M (Viboud PLoS Curr Influenza 2010)
Many difficult decisions need to be made early when limited data may be available

25. Next Steps for Severity Assessment
Efforts underway at WHO to identify new approach to severity assessment
CDC gathering input on a new framework drafted by Reed and Biggerstaff which allows for:
Data collection from early virologic and field investigations, as well as established systems
Assesment based on categories of transmission and clinical severity
Translation of the findings into context- appropriate recommendations

26. Thank You Acknowledgements
State and Local Health Departments
WHO and numerous international public health partners
CDC
Influenza Division Epidemiology and Laboratory Branches
Staff and guests assisting in the response