Summary and Impact of the 2012-2013 Influenza Season Steve Forest, - - PDF document

▶
summary and impact of the 2012 2013 influenza season
SMART_READER_LITE
LIVE PREVIEW

Summary and Impact of the 2012-2013 Influenza Season Steve Forest, - - PDF document

Sep 14, 2022 249 likes •466 views

10/3/2013 Summary and Impact of the 2012-2013 Influenza Season Steve Forest, MPH Epidemiology Research Associate Allegheny County Health Department Objectives Explain the epidemiology of seasonal influenza Discuss the 2012-13

slide-1
SLIDE 1

10/3/2013 1

Summary and Impact of the 2012-2013 Influenza Season

Steve Forest, MPH Epidemiology Research Associate Allegheny County Health Department

Objectives

  • Explain the epidemiology of seasonal

influenza

  • Discuss the 2012-13 influenza season from a

national and state perspective

  • Describe the 2012-13 influenza season impact
  • n Allegheny County

INFLUENZA REVIEW

Summary and Impact of the 2012-2013 Influenza Season

slide-2
SLIDE 2

10/3/2013 2

What is Influenza?

  • Highly infectious viral illness
  • Single-stranded RNA virus of the

Orthomyxoviridae family

  • 3 types: A,B,C
  • Subtypes of type A determined by hemagglutinin

(H) and neuraminidase (N)

– H1, H2, and H3 have a role in virus attachment to cells – N1 and N2 have a role in virus penetration into cells

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

Influenza Virus Strains

  • Type A

– humans and other animals – moderate to severe illness – all age groups – Has subtypes determined by surface antigens hemagglutinin and neuraminidase – H1N1 and H3N2 have co-circulated since 1977

  • Type B

– humans only – milder disease – primarily affects children

  • Type C

– rarely reported in humans – no epidemics

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

Influenza Virus Nomenclature

  • The nomenclature to

describe the type of influenza virus is expressed in this order:

– 1) virus type – 2) geographic origin – 3) strain number – 4) year of isolation – 5) virus subtype

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

slide-3
SLIDE 3

10/3/2013 3

Influenza Clinical Features

  • Incubation period 2 days (range 1-4 days)
  • In general, only about 50% of infected persons

will develop the classic clinical symptoms of influenza which includes:

– Abrupt onset of fever, muscle aches, sore throat, nonproductive cough, headache

  • Severity of illness depends on prior experience

with related variants

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

Influenza Complications

  • Most Commonly

– Secondary bacterial pneumonia – Exacerbation of underlying chronic health conditions

  • Less Commonly

– Primary viral pneumonia – Reye syndrome – Myocarditis

  • Death 5-10 per 10,000 cases

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

Impact of Influenza

  • Highest rates of complications and hospitalization

among young children and adults > 64 years

  • On average, >200,000 hospitalizations per year and

23,000 deaths are related to influenza

  • 90% of flu-related deaths occur in adults older than

64 years

  • Greater number of hospitalizations during type A

(H3N2) epidemics

  • The cost of a severe epidemic has been estimated to

be $12 billion

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

slide-4
SLIDE 4

10/3/2013 4 Month of Peak Influenza Activity United States, 1976-2008

Vaccination Schedule

  • Optimal time to vaccinate is BEFORE flu

activity picks up in community

  • Adults achieve peak antibody protection in 2

weeks

  • Vaccine may be given as soon as it is available
  • Providers should continue to offer vaccine

throughout flu season

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

Flu Vaccine Effectiveness

  • Flu vaccine effectiveness is affected by:

– Similarity of the vaccine strains to the circulating strains – Age and health status of the recipient

  • Flu vaccines are effective in protecting against

illness up to:

– 90% of healthy people ages 6 months to 64 years – 30-40% of adults older than 64 years

  • Among adults older than 64 years, the vaccine is:

– 50%–60% effective in preventing hospitalization – 80% effective in preventing death

Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Wolfe S, Hamborsky J, eds. 12th ed., second printing. Washington DC: Public Health Foundation, 2012.

slide-5
SLIDE 5

10/3/2013 5

2012-13 Flu Vaccine Effectiveness

  • Overall, in 2012-13, influenza vaccination reduced the risk

for medical visits resulting from

– Influenza A and B by 56% – Influenza A (H3N2) alone by 47% – Influenza B alone by 67%

  • The preventive benefits against influenza B were consistent

across all age groups

  • The preventive benefits against influenza A (H3N2) viruses

also were largely consistent for persons aged 6 months–64 years, but the benefit was not significant among adults

  • ver 64 years
  • Nevertheless, flu vaccine still remains the best preventive

tool available

Centers for Disease Control and Prevention. Interim Adjusted Estimates of Seasonal Influenza Vaccine Effectiveness – United States, February 2013. MMWR 2013;62:119-123.

Laboratory Diagnosis of Flu

  • A flu infection cannot be diagnosed accurately on signs

and symptoms alone, lab testing can confirm the diagnosis

  • Molecular detection (PCR)

– Considered the gold standard for influenza diagnosis – RT-PCR is the most sensitive method for the detection of influenza virus

  • Virus isolation (culture) and rapid culture assays

– Allows for full antigenic characterization, which is needed for determining vaccine match – Requires an average of 4.5 days to obtain results – Rapid culture assays can produce results in 18–40 hours

Centers for Disease Control and Prevention. Manual for the surveillance of vaccine-preventable diseases. Centers for Disease Control and Prevention, Atlanta, GA, 2008.

Laboratory Diagnosis of Flu

  • Antigen detection (Rapid Influenza Diagnostic Test)

– Results are available in as little as 15 minutes – RIDT are not very accurate when flu incidence in the community is low

  • Serology (antibody tests)

– Requires paired serum specimens collected several weeks apart – Nowadays there is no clinical utility to these tests – they should not be done – Diagnosis of influenza CANNOT be made from a single serum sample

Centers for Disease Control and Prevention. Manual for the surveillance of vaccine-preventable diseases. Centers for Disease Control and Prevention, Atlanta, GA, 2008.

slide-6
SLIDE 6

10/3/2013 6

Lab Based Surveillance

  • Three main types of labs:

– Commercial (Quest Diagnostics, LabCorp, etc.) – Hospital-based – Public Health Laboratories

  • Labs provide confirmation of RIDTs
  • Some labs test for novel or variant strains
  • Labs report positive test results to PA-NEDSS

PA-NEDSS

  • PA-NEDSS electronically transmits disease reports from

hospitals, laboratories, and physicians to state, district, county and municipal health departments

  • This surveillance system helps control flu by:

– Monitoring prevalence of circulating strains – Detecting new strains for vaccine formulation – Estimating influenza-related morbidity, mortality and economic loss – Rapidly detecting outbreaks

  • ACHD investigates positive flu cases who are

hospitalized, died, or pregnant, or live in a Long-Term Care Facility (LTCF)

Centers for Disease Control and Prevention. Manual for the surveillance of vaccine-preventable diseases. Centers for Disease Control and Prevention, Atlanta, GA, 2008.

Confirmed vs. Suspect

  • In Allegheny County, positive flu cases that are

investigated are further classified as confirmed or suspect

– Confirmed

  • Tested positive via culture or PCR

– Suspect

  • Tested positive via Rapid Influenza Diagnostic Test
slide-7
SLIDE 7

10/3/2013 7

Please keep in mind that laboratory-confirmed cases represent only a fraction of the total public health burden of influenza, as most people with the flu are diagnosed and treated empirically and do not have lab tests performed to determine the cause of their illness.

INFLUENZA SURVEILLANCE – UNITED STATES

Summary and Impact of the 2012-2013 Influenza Season

slide-8
SLIDE 8

10/3/2013 8

National Baseline

INFLUENZA SURVEILLANCE – PENNSYLVANIA

Summary and Impact of the 2012-2013 Influenza Season

slide-9
SLIDE 9

10/3/2013 9

Source: http://www.portal.state.pa.us/portal/server.pt/document/1353506/2012_13_season_data_pdf

Week 3

Flu Impact - Pennsylvania

  • For the 2012-13 flu season, the Pennsylvania

Department of Health reported:

– 44,00 lab positive flu cases – 3,600 hospitalizations – 200 deaths – 560 outbreaks of influenza in long-term care facilities resulting in more than 3,000 illnesses and 100 deaths among adults older than 64 years

Source: http://www.portal.state.pa.us/portal/server.pt/document/1353506/2012_13_season_data_pdf Source: http://www.portal.state.pa.us/portal/server.pt/document/1353506/2012_13_season_data_pdf

2012-13 Flu Season 2009-10 Flu Season

slide-10
SLIDE 10

10/3/2013 10

Source: http://www.portal.state.pa.us/portal/server.pt/document/1353506/2012_13_season_data_pdf

INFLUENZA SURVEILLANCE – ALLEGHENY COUNTY

Summary and Impact of the 2012-2013 Influenza Season

50 100 150 200 250 300 350 400 450 500 40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Number of Cases Week of Test Date Cases of Influenza A, B, and Other/Unspecified in Allegheny County For 2012-2013 Flu Season: 3,967 Total Cases (Data Ending Week 36 – September 7, 2013) Suspect Confirmed

Week 3

slide-11
SLIDE 11

10/3/2013 11

50 100 150 200 250 300 350 400 450 500 40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38

Number of Cases Week of Test Date Confirmed and Suspect Cases of Influenza A, B, and Other/Unspecified in Allegheny County 2008-09 Flu Season to 2012-13 Flu Season (Data Ending Week 36 – September 7, 2013)

2008-2009 2009-2010 2010-2011 2011-2012 2012-2013 2012-13 50 100 150 200 250 300 350 400 450 40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Number of Cases MMWR Week Cases of Confirmed and Suspect Influenza A and Influenza B in Allegheny County For 2012-2013 Flu Season: 3,960 Total Cases (Data Ending Week 36 – September 7, 2013)

Influenza A Influenza B

FLU SUMMARY FOR ALLEGHENY COUNTY – PREGNANCIES

Summary and Impact of the 2012-2013 Influenza Season

slide-12
SLIDE 12

10/3/2013 12

Flu Pregnancy

  • 17 pregnant women tested positive for the flu
  • 14 (82%) tested positive for Flu A
  • Influenza-like illness

– 13 (76%) reported cough – 8 (47%) reported fever > 100° F – 6 (35%) reported sore throat

  • 10 (59%) had unknown/blank seasonal flu

vaccine status

Note – the number of cases is current as of July 31st.

FLU SUMMARY FOR ALLEGHENY COUNTY – OUTBREAKS

Summary and Impact of the 2012-2013 Influenza Season

Outbreaks

  • Outbreak = 1 or more LTCF residents test positive for

flu

  • The Allegheny County Health Department learns about
  • utbreaks at LTCF in 1 of 3 ways:

– LTCF contacts us directly after 1 or more residents tests positive for the flu – ACHD receives via fax or mail a reportable disease form from LTCF – Weekly Cluster Reports generated by the Pennsylvania Department of Health

  • ACHD follows up with the facility to help control the

spread of the outbreak

slide-13
SLIDE 13

10/3/2013 13

Outbreaks

  • 53 outbreaks in 2012-

13 involving 36 facilities and 170 patients

– 41 influenza A outbreaks – 10 influenza B outbreaks – 2 influenza, unknown

  • utbreaks
  • 20 outbreaks resulted in

39 hospitalizations

  • Outbreaks lasted an

average of 10 days

20% 43% 6% 14% 16% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Number of Patients Ill per Outbreak

Outbreaks – Facility Type

78% 12% 6% 4% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Skilled Nursing Personal Care Independent Living Assisted Living

Outbreaks – Actions Taken

90% 80% 73% 67% 67% 63% 63% 63% 39% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

slide-14
SLIDE 14

10/3/2013 14 FLU SUMMARY FOR ALLEGHENY COUNTY – HOSPITALIZED CASES

Summary and Impact of the 2012-2013 Influenza Season

Flu Hospitalizations – Gender

58% 42% Female Male 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Note – the number of cases is current as of July 31st.

Flu Hospitalizations - Age Group

8% 17% 32% 14% 28% 1% 0% 14% 15% 69% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Birth to 4 5 to 17 18 to 49 50 to 64 >64 All Cases Hospitalized Cases

Note – the number of cases is current as of July 31st.

slide-15
SLIDE 15

10/3/2013 15

Flu Hospitalizations – Flu Type

84% 15% Type A Type B 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Note – the number of cases is current as of July 31st.

Flu Hospitalizations – Clinical Features

90% 65% 31%* 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Cough Fever Sore Throat

*Response Rate 60%. Note – the number of cases is current as of July 31st.

Flu Hospitalizations – Other Clinical Features

67%* 39% 19% 13% 9% 3% 2% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Average LOS = 15.8 days

*Response Rate 24%. Note – the number of cases is current as of July 31st.

slide-16
SLIDE 16

10/3/2013 16

Flu Hospitalizations – Risk Factors

80%* 73% 32% 25% 23%* 17% 12% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

*Response Rate <70%. Note – the number of cases is current as of July 31st.

Flu Hospitalizations – Treatments

85% 15% Yes No 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Tamiflu Prescribed*

*Response Rate 66%. Note – the number of cases is current as of July 31st.

Flu Hospitalizations – Protective Factors

63% 37% Yes No 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Received Seasonal Flu Vaccine*

*Response Rate 47%. Note – the number of cases is current as of July 31st.

slide-17
SLIDE 17

10/3/2013 17 FLU SUMMARY FOR ALLEGHENY COUNTY – DEATHS

Summary and Impact of the 2012-2013 Influenza Season

Flu Deaths – Gender

56% 43% 58% 42% 35% 65% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Female Male All Cases Hospitalizations Deaths

Note – the number of cases is current as of July 31st.

Flu Deaths – Age Group

8% 17% 32% 14% 28% 1% 0% 14% 15% 69% 0% 0% 10% 13% 77%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Birth to 4 5 to 17 18 to 49 50 to 64 >64 All Cases Hospitalizations Deaths

Note – the number of cases is current as of July 31st.

slide-18
SLIDE 18

10/3/2013 18

Flu Deaths – Flu Type

80% 20% 0% 84% 15% 1% 81% 10% 10% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Flu A Flu B Flu, Unspecified All Cases Hospitalizations Deaths

Note – the number of cases is current as of July 31st.

Flu Deaths – Clinical Features

65% 90% 31%* 77% 62%* 7%* 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Fever Cough Sore Throat Hospitalizations Deaths

*Response Rate <70%. Note – the number of cases is current as of July 31st.

Flu Deaths – Other Clinical Features

39% 19% 67%* 9% 13% 2% 0% 73% 70% 63%* 45%* 26%* 10%* 5%*

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Hospitalizations Deaths

*Response Rate <70%. Note – the number of cases is current as of July 31st.

slide-19
SLIDE 19

10/3/2013 19

Flu Deaths – Risk Factors

73% 80%* 32% 25% 12% 23%* 17% 90%* 67%* 41% 38%* 27%* 8%* 6%*

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Hospitalizations Deaths

*Response Rate <70%. Note – the number of cases is current as of July 31st.

Flu Deaths – Treatments

88% 12% Yes No 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Tamiflu Prescribed*

*Response Rate 52%. Note – the number of cases is current as of July 31st.

Flu Deaths – Protective Factors

67% 33% Yes No 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Received Seasonal Flu Vaccine*

*Response Rate 39%. Note – the number of cases is current as of July 31st.

slide-20
SLIDE 20

10/3/2013 20

Contact Information

Steve Forest, MPH Epidemiology Research Associate Office of Epidemiology and Biostatistics Allegheny County Health Department Work: (412) 578-8345 Fax: (412 578-8025 E-mail: sforest@achd.net