Influenza Surveillance Before and During a Pandemic

1
Influenza Surveillance Before and During a
Pandemic

• Daniel B. Jernigan, MD MPH
• Deputy Director
• Influenza Division
• National Center for Immunization
• and Respiratory Diseases
• CCID

2
Seasonal Influenza - Burden

• Significant Annual Disease Burden in U.S.
• Infects 5 20 of the US population
• 200,000 hospitalizations
• 36,000 deaths
• Annual public health challenge
• Vaccination 218 M now recommended
• Each season we start over

3
Seasonal Influenza - Surveillance

• Surveillance is critical to monitor
• Where and which type of flu is circulating
• Intensity and impact of flu activity
• Effectiveness of vaccines and antivirals
• Novel strains with pandemic potential to assure
  rapid intervention

4
Surveillance for Influenza

• Tracking the Virus
• Tracking Clinical Illness
• Tracking Mortality
• Tracking Cases during a Pandemic

5
Surveillance for Influenza

• Tracking the Virus
• Tracking Clinical Illness
• Tracking Mortality
• Tracking Cases during a Pandemic

6
Tracking the Virus

• CDC-Sponsored Laboratory Network
• WHO Collaborating Laboratories
• National Respiratory and Enteric Virus
  Surveillance System (NREVSS)
• 130 participating labs
• Average of 175,000 tests done per year
• For the 2006-07 season
• 23,181 typed as influenza A or B
• 6,035 subtyped (e.g., H3N2, H1N1)
• Antiviral resistance is monitored

7
Tracking the Virus
WHO-NREVSS Laboratory Surveillance Updated Week
20 (May 13 19, 2007)
8
Tracking the Virus

• Novel Influenza Virus Surveillance
• New CSTE reportable condition
• Improves reporting of strains of pandemic
  potential
• Facilitates early initiation of appropriate
  public health responses

9
Surveillance for Influenza

• Tracking the Virus
• Tracking Clinical Illness
• Tracking Mortality
• Tracking Cases during a Pandemic

10
Tracking Clinical Illness Outpatient
Sentinel Provider Network

• Monitor Influenza-Like Illness (ILI)
• 2,400 healthcare providers in 50 states
• 12 million patient visits each year
• Subset provides clinical specimens

11
Tracking Clinical Illness Hospitalizations and
Severe Disease

• Emerging Infections Program (EIP)
• Population-based surveillance
• Children and adults with lab-confirmed flu
• 60 counties in 12 metro areas in 10 states (CA,
  CO, CT, GA, MD, MN, NM, NM, NY, OR, TN)
• New Vaccine Surveillance Network (NVSN)
• Population-based surveillance
• Children lt5 yrs with lab-confirmed flu
• Three counties in OH, TN, NY

12
Tracking Clinical Illness State-Level
Influenza Activity

• Weekly report from state epidemiologists
• Rank flu activity into 6 levels based on
• ILI
• Lab-confirmed cases

13
Surveillance for Influenza

• Tracking the Virus
• Tracking Clinical Illness
• Tracking Mortality
• Tracking Cases during a Pandemic

14
Tracking Mortality Death Record Reporting

• Weekly reports from vital statistics offices
• In place for 40 years
• New efforts to migrate to electronic death record
  reporting

122 Cities Mortality Reporting System
15
Tracking Mortality Death Record Reporting
122 Cities Mortality Reporting System
Epidemic Threshold
Seasonal Baseline
2004
2005
2006
2003
21 30 40 50 10 20 30
40 50 10 20 30
40 50 10 20 30 40
50 10 20
Updated Week 20 (May 13 19, 2007)
16
Tracking Mortality Pediatric Deaths

• Pediatric mortality associated with influenza
• Nationally notifiable disease
• Initiated after 2003-04 season when over 150
  children died of influenza
• Lab-confirmed cases under 18 yrs due to influenza
  should be reported to public health authorities

17
Surveillance for Influenza

• Tracking the Virus
• Tracking Clinical Illness
• Tracking Mortality
• Tracking Cases during a Pandemic

18
Tracking Cases during Pandemic

• Case-Contact Tracing Activity
• For early response using CDC-OMS
• Detect cases for isolation/treatment
• Detect contact for quarantine/prophylaxis
• State Pandemic Influenza Summary Reports
• Regular reports during pandemic
• Aggregate case counts

19
(No Transcript)
20
Pandemic Influenza Definition

• Novelty severe infection with an influenza A
  virus for which there is no existing immunity in
  the population
• Efficiency clinical attack rates are in the
  range of seasonal influenza
• Sustainability transmission from person to
  person to person is maintained

21
Pandemic Influenza Burden

• Appear in the human population periodically
• H5N1 is a likely candidate, but is not a pandemic
  virus yet
• Past pandemics fatality
• 1918 40-50 million deaths, 500K in US
• 1957 2 million deaths, 70K in US
• 1968 1-4 million deaths, 34K in US

22
Federal Pandemic Plans

• National Strategy for Pandemic Influenza
• Homeland Security Council Implementation Plan for
  the National Strategy for Pandemic Influenza
• HHS Pandemic Influenza Plan
• Community Strategy for Pandemic Influenza
  Mitigation (pandemicflu.gov)

23
Potential Strategies to Decrease the Impact of a
Pandemic

• Slow spread (Buy time)
• Decrease illness and death
• Antiviral treatment and isolation for people with
  illness
• Quarantine for those exposed
• Social distancing, School closures
• Vaccine when available

24
Pandemic Severity Index
25
Importance of Mortality Data During a Pandemic

• Early in pandemic emergence
• Determine Case Fatality Ratio to categorize
  severity
• Availability of data uncertain
• WHO
• Ministries of Health
• Vital registrars in US
• Rapid investigation of outbreak
• At peak transmission of pandemic
• Virologic and case-based tracking unlikely to be
  possible
• Mortality and ILI monitoring can provide
  estimates of pandemic activity

26
Surveillance during a Pandemic

• Consider a simplified pandemic curve
• How would surveillance for influenza need to
  change as the pandemic progresses

27
Surveillance during a Pandemic

• Different communities will be at different
  intervals during the pandemic
• State or community level planning may need a
  locally-defined trigger
• National curve is simply summation of state/local
  curves

28
Surveillance during a Pandemic

• Pandemic Intervals
• A) Introduction
• B) Acceleration
• C) Peak Transmission
• D) Deceleration
• E) Resolution

29
Surveillance during a Pandemic
Introduction Interval

• Virologic Surveillance
• Real Time Reporting
• Increased Testing
• Pandemic Case Investigation
• Case/Contact intervention
• State reporting
• Mortality Reporting
• Daily if possible (electronic!)
• Clinical Illness Monitoring
• Daily reports from Super Sentinel Providers

30
Surveillance during a Pandemic
Acceleration Interval

• Virologic Surveillance
• Real Time Reporting
• Shifting to Sampling Testing
• Clinical Illness Monitoring
• Daily ILI reports from Super Sentinel Providers
• Utilize syndromic surveillance data if available
• Mortality Reporting
• Daily if possible (electronic!)
• Pandemic Case Investigation
• Case/Contact intervention slows
• State reporting of aggregate data

31
Surveillance during a Pandemic
Peak Transmission Interval

• Mortality Reporting
• Daily if possible (electronic!)
• Clinical Illness Monitoring
• ILI reports from Sentl Provs
• Synd. Surv. data if available
• Pandemic Aggregate Reports
• Case/Contact tracing stops
• State activity maps are reported
• Virologic Surveillance
• Real Time Reporting
• Decreased numbers of tests

32
Conclusions

• Influenza surveillance in the US is accomplished
  through a collection of systems to track viruses,
  clinical illness, and mortality.
• These existing systems, along with additional
  case investigation and reporting systems, will be
  used during a pandemic.
• Systems will vary in use according to the
  pandemic intervals
• Improvements in mortality reporting and other
  surveillance systems will improve pandemic
  preparedness.

33
Thank You

• Daniel B. Jernigan, MD MPH
• DJernigan_at_cdc.gov
• Deputy Director
• Influenza Division
• National Center for Immunization
• and Respiratory Diseases, CCID