Influenza Surveillance in the United States Oliver Morgan, PhD MSc Division of Emerging Infections...

Influenza Surveillance in the United States

Oliver Morgan, PhD MScDivision of Emerging Infections and Surveillance Services

Dr. Lyn Finelli, Scott Epperson

Influenza Division

Centers for Disease Control and Prevention

Objectives of Influenza Surveillance

• Determine which influenza viruses are circulating; where are they circulating; when are they circulating

• Determine intensity and impact of influenza activity

• Detect unusual events– Infection by unusual viruses– Unusual syndromes caused by influenza viruses– Unusually large/severe outbreaks

Influenza Surveillance

• Responsibility for national influenza surveillance rests with CDC

• State and local public health departments are our primary partners

• Review of surveillance held in 2006 & 2007 with Council of State and Territorial Epidemiologists (CSTE)– Build a system that is useful on the local level and

builds to national level surveillance

The Five Categories of Influenza Surveillance

• Viral Surveillance• Mortality Surveillance • Hospitalization Surveillance• Outpatient Illness Surveillance• Summary of the Geographic Spread of Influenza

http://www.cdc.gov/flu/weekly/


• Viral Surveillance– WHO (World Health Organization) and NREVSS

(National Respiratory and Enteric Virus Surveillance System) Collaborating Laboratories

– Novel influenza A virus surveillance

• Mortality Surveillance • Hospitalization Surveillance• Outpatient Illness Surveillance• Summary of the Geographic Spread of Influenza

Viral Surveillance

• Viral surveillance is the foundation for influenza control efforts– Identify changes in circulating strains

• Future vaccine strain selection• Assess current vaccine match• Identify viruses with pandemic potential

– Establish seasonality• Timing of active surveillance• Timing of influenza control activities

Virologic Surveillance in the U.S.• ~150 participating laboratories

– Specimens collected during routine patient care – Weekly reports

• # specimens tested• # positive for influenza: type, subtype, age

• Novel influenza A reporting– Made nationally notifiable condition in 2007

• WHO Collaborating Labs– ~ 85 labs– Maintained by ID/CDC– State health dept.,

universities, large tertiary care hospital labs, and DoD

– Subtype influenza A – Report age data– Send subset of isolates to

CDC for further testing

• NREVSS labs– ~ 65 labs– Maintained by DVD/CDC– Hospital labs– Report data on other

respiratory viruses– Less likely to subtype

influenza A viruses– Don’t report age data– Data incorporated into flu

surveillance since 97-98

U.S. Virologic Surveillance:Participating Labs

Viral Strain Surveillance

• WHO labs submit subset of isolates to CDC strain surveillance lab

• Detailed antigenic characterization• Sequencing of some isolates• Antiviral resistance testing

– Adamantanes - when needed– Neuraminidase inhibitors - large subset

U.S. WHO/NREVSS Collaborating Laboratories National Summary, 2008-09

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40 42 44 46 48 50 52 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35

Week

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55A (Pandemic H1N1)

A (Unable to Subtype)A (H3)

A (H1)A (Subtyping not Performed)

BPercent Positive


• Viral Surveillance• Mortality Surveillance

– 122 Cities Mortality Reporting System– Influenza-Associated Pediatric Deaths

• Hospitalization Surveillance• Outpatient Illness Surveillance• Summary of the Geographic Spread of Influenza

122 Cities Mortality Reporting System

• Purpose: monitor P&I related mortality in a timely manner

• Weekly reports from vital statistics offices in 122 US cities– Total # of death certificates filed– # with pneumonia or influenza listed anywhere

• ~ 1/4 of US deaths

Pneumonia and Influenza Mortalityfor 122 U.S. Cities

Week Ending 07/04/2009

4

6

8

10

21 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20 30 40 50 10 20

Surveillance Weeks

% o

f All

Dea

ths

Due

to P

&I

2007 200820062005 2009

Epidemic Threshold

Seasonal Baseline

Pediatric Influenza-Associated Mortality Reporting

• In June 2004, CSTE adopted proposal to make influenza-associated death in a person <18 yrs. a nationally notifiable condition.– Reporting began in October 2004– Data reported weekly in MMWR and FluView

Number of Influenza-Associated Pediatric Deaths by Week of Death

Week ending 07/04/2009

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9

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2005

-40

2005

-46

2005

-52

2006

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2006

-12

2006

-18

2006

-24

2006

-30

2006

-36

2006

-42

2006

-48

2007

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2007

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2007

-14

2007

-20

2007

-26

2007

-32

2007

-38

2007

-44

2007

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-04

2008

-10

2008

-16

2008

-22

2008

-28

2008

-34

2008

-40

2008

-46

2008

-52

2009

-05

2009

-11

2009

-17

2009

-23

Week of Death

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eath

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Deaths Reported Current Week

Deaths Reported Previous Weeks

Pandemic Influenza A (H1N1) Deaths Reported Current Week

Pandemic Influenza A (H1N1) Deaths Reported Previous Weeks


• Viral Surveillance• Mortality Surveillance• Hospitalization Surveillance

– Emerging Infections Program (EIP)– New Vaccine Surveillance Network (NVSN)

• Outpatient Illness Surveillance• Summary of the Geographic Spread of Influenza

Hospitalization Surveillance

• Emerging Infections Program

– All ages– Lab tests as part of routine

patient care– Chart reviews

• New Vaccine Surveillance Network

– 0 – 4 year olds– Children admitted with fever

or acute respiratory illness are swabbed and tested

– Culture and PCR– Chart reviews

• Population-based surveillance for laboratory confirmed influenza related hospitalizations


• Viral Surveillance• Mortality Surveillance• Hospitalization Surveillance• Outpatient Illness Surveillance

– U.S. Influenza Sentinel Provider Surveillance Network (ILINet)

• Summary of the Geographic Spread of Influenza

Outpatient Influenza Surveillance (ILINet)

• ~2,400 healthcare providers in 50 states

• Weekly reports

– Total # of patient visits

– # visits for influenza-like illness (ILI) by age group

• ILI = fever 100 ºF (37.8 ºC) and cough or sore throat, in absence of a known cause other than influenza

• Early, peak, and late season

Percentage of Visits for Influenza-like Illness (ILI) Reported by ILINet

Week ending 07/04/2009

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3

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40 42 44 46 48 50 52 1 3 5 7 9 11 13 15 17 19 21 23 25

Surveillance Week

% o

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isits

fo

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I

2006-07* 2007-08* 2008-09 National Baseline

Note: There was no week 53 during the 2006-07 and 2007-08 seasons, therefore the week 53 data point for those seasons is an average of weeks 52 and 1.


• Viral Surveillance• Mortality Surveillance• Hospitalization Surveillance• Outpatient Illness Surveillance• Summary of the Geographic Spread of Influenza

Geographic Spread of Influenza

• Weekly reports from State and territorial epidemiologists

• Assessment of overall influenza activity at state level– None, sporadic, local, regional, or widespread– Incorporates virologic and ILI data– Only system reporting state-level data

• Allows local interpretation of surveillance data

Influenza Surveillance Challenges

• Not everyone with influenza accesses healthcare

• Can’t distinguish influenza from other respiratory viruses on clinical criteria– Most cases are not tested / lab confirmed

• Volume – can’t test all respiratory cases

• Not all cases will test positive– Many cases with severe influenza-related complications

(hospitalization or death)– Timing of sample collection not optimal

• Surveillance reports must be timely

Goals of Pandemic Influenza Surveillance

1. Identify and track viruses/strains

2. Describe clinical infections

3. Determine who is affected and the severity of the pandemic

4. Detect the onset and duration of the pandemic and the geographic spread

5. Guide interventions

6. Provide information to partners

Pandemic Influenza Intervals

DAccel-eration

CInitiation

EPeak

TransmissionF

DecelerationG

Resolution

BRecognition

AInvestigation

Pandemic Surveillance Framework

• Pandemic intervals as framework• Develop interval-specific surveillance strategy based on

information we need for action• Use combinations of surveillance systems to collect the

data necessary to address the goals of surveillance for each interval

• Feasible and sustainable approach to pandemic surveillance

Interval AInvestigation

Interval AReporting Frequency

WHO & NREVSS Collaborating Laboratories

Weekly

Novel Influenza A Virus Infections Daily

122 Cities Mortality Reporting System

Weekly

Influenza Associated Pediatric Mortality

Daily

EIP Influenza Surveillance Network Bi-Weekly

New Vaccine Surveillance Network Bi-Weekly

State and Territorial Epidemiologists Report

Weekly

Sentinel Provider Surveillance Network

Weekly

Aggregate case reporting NR

DC E F G

BA

Triggers Identification of human cases of novel influenza A

Federal Actions Maintain surveillance Support investigation/containment Characterize viruses

Interval BRecognition

Interval BReporting Frequency

WHO & NREVSS Collaborating Laboratories (subset)

Daily


122 Cities Mortality Reporting System (web-based)

Daily


Daily

EIP Influenza Surveillance Network Bi-Weekly

New Vaccine Surveillance Network Bi-Weekly


Weekly

Sentinel Provider Surveillance Network (subset)

Daily

Aggregate Case Reporting NR

Triggers Confirmation of human cases and demonstration of efficient and sustained human to human transmission

Federal Actions Maintain surveillance Deploy responders Evaluate case fatality ratio and PSI

DC E F G

BA

Interval CInitiation

Interval CReporting Frequency


Daily



Daily


Daily

EIP Influenza Surveillance Network Weekly

New Vaccine Surveillance Network Weekly


Daily


Daily

Aggregate Case Reporting NR

Triggers Laboratory confirmed human cases detected in any state

Federal Actions Maintain surveillance Conduct lab confirmation and characterize viruses Deploy responders/SNS Evaluate case fatality ratio and PSI

DC E F G

BA

Interval DAcceleration

Interval DReporting Frequency


Daily

Novel Influenza A Virus Infections Daily-NR


Daily


Daily




Daily


Daily

Aggregate Case Reporting Daily

Triggers Multiple laboratory confirmed cases in a state without epi-link

Federal Actions Maintain surveillance Conduct lab confirmation and characterize viruses (targeted) Studies of clinical course Evaluate case fatality ratio and PSI

DC E F G

BA

Interval EPeak Transmission

Interval EReporting Frequency


Daily

Novel Influenza A Virus Infections NR


Daily


Daily




Daily


Daily

Aggregate Case ReportingDaily-Weekly

Triggers >10% specimens submitted from states + for pandemic strain

Federal Actions Continue virologic characterization Maintain surveillance Transition to surveillance for mortality and syndromic disease

DC E F G

BA

Interval FDeceleration

Interval FReporting Frequency


Daily



Daily


Daily




Daily


Daily

Aggregate Case ReportingDaily-Weekly

Triggers <10% specimens submitted from states + for pandemic strain

Federal Actions Continue virologic characterization Maintain surveillance for mortality and syndromic disease

DC E F G

BA

Interval GResolution

Interval GReporting Frequency


Weekly



Weekly


Daily




Weekly


Weekly

Aggregate Case Reporting Weekly-NR

Triggers <1% specimens submitted from states + for pandemic strain during a two-week period

Federal Actions Return to routine virologic testing Maintain surveillance for mortality and syndromic disease

DC E F G

BA

Pandemic Surveillance

DAccel-eration

CInitiation

EPeak

TransmissionF

DecelerationG

Resolution

BRecognition

AInvestigation

Rapid spread within a jurisdiction Multiple lab-confirmed cases w/o an epi link

?

Surveillance Realities

• Few hospitalizations and deaths– Rethink our strategy

• Mild to moderate clinical illness

• Age distribution of cases and persons hospitalized similar to that of seasonal H1N1

Surveillance Realities

• Needed to re-focus surveillance– ILINet has been our lifeline to influenza activity

– Aggregate reports and line listed data• Limited by testing practices

– Need for information about burden of illness and clinical spectrum• Community Household Surveys

– Need for information about what states are doing and can do• Rapid Survey of Surveillance Activities in states• ILINet, other systems, lab and testing

Surveillance Planning

• Dynamic situation– Information requirement modulated by

• pandemic interval• severity of illness• planning public health interventions (vaccine, hospital surge,

stockpile)• hypothesized “mixed” season with 5 viruses circulating• hypothesized increase in transmissibility of the virus


• Summer– Option 1 Current Strategy

• Weekly aggregate reporting• ILINet (subset)• Automated syndromic systems• WHO/NREVSS daily (subset)

– Option 2 Scale back• D/C weekly aggregate reporting (states post case counts?)• ILINet Weekly• WHO/NREVSS weekly


• Fall– Option 1 Continue Current Summer Strategy

• Weekly aggregate reporting• ILINet daily (subset)• Automated syndromic systems (BioSense, etc)• WHO/NREVSS daily (subset)

– Option 2 Scale Up• Return to daily line listed case reporting or web based CRF

– Staggered reporting of CRF• Hospitalization case reporting (long or shorter form)

– First “200” or EIP if widespread• Other systems daily

Next steps

• Convene CSTE working group comprised of state Epidemiologists and surveillance coordinators

Additional Information

• CDC/Influenza Division FluView surveillance report– Weekly from October through mid-May– http://www.cdc.gov/flu/weekly/fluactivity.htm

• General influenza information– http://www.cdc.gov/flu/

• Avian influenza information– http://www.cdc.gov/flu/avian/

• Pandemic influenza– http://www.pandemicflu.gov/

West SouthCentral - 7

Pacific - 9

Mountain - 8West NorthCentral - 4 East North

Central - 3 Mid Atlantic - 2

New England - 1

South Atlantic - 5

East South Central - 6

Pacific - 9

Influenza Surveillance Regions

Number of Specimens Tested for Influenza and Number Positive

Season All labs

# tested # positive

2002-03 96,871 9,841

2003-04 152,262 25,104

2004-05 186,478 24,501

2005-06 180,961 21,497

2006-07 189,415 23,941

2007-08 * 235,436 40,167

*data as of July 18, 2008

National Center for Health Statistics Mortality Data

• Provides a complete and more detailed record of cause of death

• > 99% of all deaths in the US• Separate record for each individual

– Basic demographic data– Date of death– Underlying & contributing causes of deaths

• Data used for special studies – Mortality estimates obtained from mathematical modeling

• Not available until ~ 2 yrs later

Growth of the Influenza Sentinel Physician Surveillance System

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1996-97 1997-98 1998-99 1999-2000

2000-01 2001-02 2002-03 2003-04 2004-05 2005-06 2006-07 2007-08

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enrolled physicians regularly reporting physicians patient visits

*

* As of 7/18/2008

Percentage of Visits for ILI Reported by Sentinel Providers,National Summary, 1997-98 – 2007-08

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97

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-08

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-18

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-47

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-05

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-15

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-44

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-02

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-12

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03

-41

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-51

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-09

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-48

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-06

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-16

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-15

Week

% o

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99-00 00-01 01-02 02-03 03-04 04-05 05-06 06-07 07-0898-9997-98

Influenza Activity Levels

• No Activity: No laboratory-confirmed cases of influenza and no reported increase in the number of cases of ILI

• Sporadic: Small numbers of laboratory-confirmed influenza cases or a single influenza outbreak has been reported, but there is no increase in cases of ILI

• Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state

• Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least 2 but less than half the regions of the state

• Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state

. .. ..

Current Status of WHO System

• >175,000 isolates/yr (600 to 1200 M cases)• WHO CCs receive 6,500 – 8,000 samples/yr.• WHO CCs and NICs sequence HA of 1,000

samples/yr; complete genomes now sequenced (e.g, members of GIP sequenced complete genomes of 20 H5N1 viruses in few weeks)

• >290 M doses of influenza vaccine w/wide

2007-08 Surveillance Summaries

U.S. WHO/NREVSS Collaborating Laboratories National Summary, 2007-08

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B

Percent Positive

Influenza Surveillance in the United States Oliver Morgan, PhD MSc Division of Emerging Infections...

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