Influenza, 2009 Danae Bixler, MD, MPH Division of Infectious Disease Epidemiology.

Influenza, 2009

Danae Bixler, MD, MPHDivision of Infectious Disease

Epidemiology

Objectives

• Summarize 2009 respiratory outbreaks in West Virginia

• Review recently released information on novel influenza A (H1N1)– Epidemiology– Outbreaks– Hospitalizations

• Review an outbreak of Streptococcal pharyngitis

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Respiratory Outbreaks, 2009(provisional)

• 53 outbreaks reported by 31 (56%) counties– 25 (47%) 2009 influenza A (H1N1)– 9 (17%) Influenza-like illness– 5 (9%) Influenza A– 5 (9%) Upper respiratory illness– 3 (6%) Group A Streptococcus– 2 (4%) Influenza B– 4 other …

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2009 Influenza A (H1N1)

• April 24, 2009 MMWR– 2 human cases of swine-origin influenza in

Southern California• No history of swine contact• ILI in family contacts

• May 1, 2009 MMWR– Cases in California, Texas• Not linked to each other• Not linked to outbreak in Mexico

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2009 Influenza A (H1N1)NEJM, 2009; 361:115

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H1N1 Descriptive EpidemiologyEuro Surveill, 2009: 14(22):pii=19232

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H1N1 Descriptive EpidemiologyEuro Surveill, 2009: 14(22):pii=19232

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Pediatric Hospitalization, ArgentinaNEJM, 2010, 362:45

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Pediatric Hospitalization, ArgentinaNEJM, 2010, 362:45

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Household TransmissionNEJM, 2009, 361:2628

May 28, 2009:• 938 probable/confirmed H1N1 case reports– 533 (57%) households had two to six members

• 216 (41%) households without missing information– 600 household contacts.

• Acute respiratory illness = 2 or more of: – Fever– Cough– Sore throat or – Runny nose

• Secondary cases occurred within 7 days.

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Transmission of Acute Respiratory Illness in Households

•Median age in households = 26 years•Median age of secondary cases = 16.5 years•AR = 28% in households with 2 members•AR = 9% in houssholds with 6 members

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Variable Estimated Odds Ratio(95% CI)

P Value

Age of household contact

0-4 years 3.52 (1.55 – 7.97) 0.003

5-18 years 2.01 (1.11 – 3.63) 0.03

19-50 years 1.00

> 51 years 0.41 (0.08 – 2.04) 0.28

Doubling of household size 0.27 (0.14 – 0.52) <0.001

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WEST VIRGINIA EXPERIENCE2009 Influenza A (H1N1)

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Approach to Influenza Outbreak Investigation

1. Prepare for field work2. Establish the existence of an outbreak2. Establish the existence of an outbreak3. Verify the diagnosis3. Verify the diagnosis4. Construct a working case definition4. Construct a working case definition5. Find cases systematically and record information5. Find cases systematically and record information6. Perform descriptive epidemiology7. Develop hypotheses8. Evaluate hypotheses epidemiologically9. As necessary, reconsider, refine, and re-evaluate hypotheses10. Compare and reconcile with laboratory and/or environmental studies11. Implement control and prevention measures11. Implement control and prevention measures12. Initiate or maintain surveillance12. Initiate or maintain surveillance13. Communicate findings13. Communicate findings

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Line list # 1

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Line list # 6

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General Measures for Congregate Settings with Healthy Individuals…

(CDC)

• Keep / send ill persons home• Encourage– Respiratory etiquette– Hand hygiene

• Routine environmental cleaning• Leave policies– Don’t require MD note– Don’t reward perfect attendance

• Educate persons with underlying conditions

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Control of Influenza in Long Term Care

• Pre-season immunization of patients and staff• Isolation of ill persons• Secure the diagnosis rapidly– 8-10 specimens from recently ill persons

• Begin antiviral prophlaxis according to recommendations

• Continued surveillance to assess impact of control measures

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OUTBREAKS IN THE CURRENT LITERATURE

2009 Influenza A (H1N1)

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Outbreak in a New York City High SchoolNEJM, 2009 361:2628

• Thursday, April 23, 2009– 100 of 2686 high school students ill– Fever, headache, dizziness, sore throat, respiratory

symptoms• Friday, April 24, 2009: health department team

dispatched– NP and OP specimens– School event for April 24 cancelled

• Sunday, April 26: CDC confirmed H1N1• April 25-May 3: School closed

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MethodsNEJM, 2009 361:2628

• NP swabs for RT-PCR• On-line survey of students– Recruitment by mass e-mail– Phone contact for persons with worsening illness

• Case = fever + cough or sore throat

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•119 confirmed cases•2 hospitalized with LOS = 1 day

NEJM, 2009 361:2628

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•124 laboratory-confirmed cases•105 (85%) reported ILI•5 (4%) laboratory-confirmed cases without ILI

NEJM, 2009 361:262832

EpidemiologyNEJM, 2009 361:2628

Incubation Period Duration of Illness

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•5% developed symptoms by 0.9 days•50% by 1.4 days•95% by 2.2 days

Summary: incubation period = 1-2 days

•50% recovered by 6 days•75% recovered by 9 days

Summary: recovery takes as much as 1-2 weeks

NYC Schools Influenza Outbreak Investigation

1. Prepare for field work1. Prepare for field work2. Establish the existence of an outbreak2. Establish the existence of an outbreak3. Verify the diagnosis3. Verify the diagnosis4. Construct a working case definition4. Construct a working case definition5. Find cases systematically and record information5. Find cases systematically and record information6. Perform descriptive epidemiology6. Perform descriptive epidemiology7. Develop hypotheses8. Evaluate hypotheses epidemiologically9. As necessary, reconsider, refine, and re-evaluate hypotheses10. Compare and reconcile with laboratory 10. Compare and reconcile with laboratory and/or environmental studiesstudies11. Implement control and prevention measures11. Implement control and prevention measures12. Initiate or maintain surveillance12. Initiate or maintain surveillance13. Communicate findings13. Communicate findings

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Influenza A 2009 (H1N1) in Nursing Homes

MMWR, 2010; 59:74-77.

• 3 nursing home outbreaks:– ILI attack rates:• Residents: 6% - 28%• Staff: 5% - 40%

– Control• Oseltamivir prophylaxis• Droplet precautions• Hand hygiene and cough etiquette• Restrict new admissions and visitors

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Influenza Prevention and Control Guidelines for Nursing Homes

MMWR, 2010; 59:74-77.• VaccinateVaccinate health-care personnel against seasonal influenza and 2009

pandemic influenza A (H1N1). Vaccinate residents of long-term--care facilities for seasonal influenza and offer 2009 H1N1 as this vaccine becomes widely available.

• Instruct all residents and staff members to use respiratory hygiene respiratory hygiene and cough etiquettecough etiquette.

• Restrict ill visitors and ill health-care personnel Restrict ill visitors and ill health-care personnel from the facility.• Continue active surveillance and use influenza testing Continue active surveillance and use influenza testing for new cases of

acute respiratory illness and influenza-like illness.• To the extent possible, segregate ill residents segregate ill residents from unaffected residents

and maintain appropriate levels of isolationappropriate levels of isolation. • When influenza is detected in the facility, administer influenza antiviral administer influenza antiviral

treatmenttreatment to ill residents and influenza antiviral prophylaxis and influenza antiviral prophylaxis to unaffected residents. Unaffected health-care personnel should be offered influenza antiviral prophylaxis.

SOURCES: CDC. Interim guidance on infection control measures for 2009 H1N1 influenza in healthcare settings, including protection of healthcare personnel; October 14, 2009. Available at http://www.cdc.gov/h1n1flu/guidelines_infection_control.htm. Carman WF, Elder AG, Wallace LA, et al. Effects of influenza vaccination of health-care workers on mortality of elderly people in long-term care: a randomised controlled trial. Lancet 2000;355:93--7.

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http://www.cdc.gov/h1n1flu/guidelines_infection_control.htm

GROUP A STREPTOCOCCAL PHARYNGITIS

Langiappe

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GAS Pharyngitis

• Acute pharyngotonsillitis– Fever– Sore throat

• Complications– Scarlet fever– Rheumatic fever– Acute glomerulonephritis– Purulent complications: otitis media, sinusitis,

peritonsillar and retropharyngeal abcesses, suppurative cervical adenitis

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GAS Pharyngitis

• Transmission: – Person-to-person– Foodborne– No fomite or zoonotic transmission

• Colonization– 15% of asymptomatic children– Persist for months– Transmission is minimal

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GAS pharyngitis diagnosis

• Who should be tested?– Acute onset– Fever– Clinical signs and symptoms or exposure• Pharyngeal exudate• Pain on swallowing• Enlarged tender anterior cervical nodes

• Do not test children with viral syndrome:– Coryza, conjunctivitis, hoarseness, cough, etc.

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Line List

Grade FeverSore Throat

Rapid Positive

Culture Positive Student/Staff

Diagnosis Date

K y y y y Student 5/1/2009

K y y y Student 5/1/2009

1 y y y Student 5/1/2009

K y y y y Student 5/3/2009



3 y y y y Student 5/4/2009



y y y Staff 5/4/2009

y y y Staff 5/4/200941

GAS Pharyngitis Outbreak Investigation

1. Prepare for field work1. Prepare for field work2. Establish the existence of an outbreak2. Establish the existence of an outbreak3. Verify the diagnosis3. Verify the diagnosis4. Construct a working case definition4. Construct a working case definition5. Find cases systematically and record information5. Find cases systematically and record information6. Perform descriptive epidemiology6. Perform descriptive epidemiology7. Develop hypotheses8. Evaluate hypotheses epidemiologically9. As necessary, reconsider, refine, and re-evaluate hypotheses10. Compare and reconcile with laboratory 10. Compare and reconcile with laboratory and/or environmental studiesstudies11. Implement control and prevention measures11. Implement control and prevention measures12. Initiate or maintain surveillance12. Initiate or maintain surveillance13. Communicate findings13. Communicate findings

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Conclusions

• We survived … (the 1st wave).• Experience with seasonal influenza

surveillance / outbreak investigation was an excellent model for pandemic response

• Outbreak investigation is good practice for the next public health emergency

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For most basic outbreaks:

2. Establish the existence of an outbreak2. Establish the existence of an outbreak3. Verify the diagnosis3. Verify the diagnosis11. Implement control and prevention 11. Implement control and prevention

measuresmeasures12. Initiate or maintain surveillance12. Initiate or maintain surveillance13. Communicate findings13. Communicate findings

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Influenza, 2009 Danae Bixler, MD, MPH Division of Infectious Disease Epidemiology.

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