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

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

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

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

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

Early Estimate of Symptomatic Case Fatality Ratio Reed, Biggerstaff – CDC unpublished data

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

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

Pandemic Severity Index Benchmarked to Past Pandemic Mortality

During the Summer

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

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

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

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

Through the Fall Wave

CDC Virologic Surveillance through the Fall Wave 2008 2009 16

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

Visits for ILI surpassed prior seasons, notably among younger age groups 2009-10 2007-08 Schools Start 2006-07 2008-09

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

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 2005-06 2006-07 2007-08 2008-09 2009-10

Number of Influenza-Associated Laboratory-Confirmed Pediatric Deaths 2007-08 88 Pediatric Deaths 2008-09 69 Pediatric Deaths 21

Number of Influenza-Associated Laboratory-Confirmed Pediatric Deaths 4 – 5 times more than prior seasons Since H1N1 344 Pediatric Deaths 2007-08 88 Pediatric Deaths 2008-09 69 Pediatric Deaths 22

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

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

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

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