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Novel Influenza A (H1N1): Impact on Schools, Spring, 2009

30 July 2009

Francisco Averhoff MD, MPHCommunity Measures Task Force

Division of Global Migration and QuarantineCenters for Disease Control and Prevention

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Basis for Recommendations: Non-Pharmaceutical Interventions (NPIs)

• Evidence from 1918 pandemic

• Epidemiologic studies

• Modeling

• Common Sense

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Non-Pharmaceutical Interventions (NPIs)*

• Isolation and treatment of ill persons• Voluntary home quarantine of

household contacts• Dismissal of students from school and

social distancing and daycare closure• Workplace/community social distancing

* Targeted Layered Containment (TLC):The sum likely to be greater than the parts…

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Factors that Impact Transmission and Reproductive Rate (Ro)*

• Infectiousness of the infected• Susceptibility of uninfected• Interactions, contact and behaviors of

the population- target of interventions

* Goal is Ro < 1, results in decreasing epi curve and end of outbreak/epidemic

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Effect of R on Hypothetical Epidemic Curves

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Community-Based Non Pharmaceutical Interventions (NPIs)

1. Delay disease transmission and outbreak peak2. Decompress peak burden on healthcare infrastructure3. Diminish overall cases and health impacts

DailyCases

#1

#2

#3

Days since First Case

Pandemic outbreak:No intervention

Pandemic outbreak:With intervention

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Collins SD, Frost WH, Gover M, Sydenstricker E: Mortality from influenza and pneumonia in the 50 largest cities of the United States First Edition Washington: U.S. Government Printing Office 1930.

1918 Death Rates: Philadelphia v St. Louis

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Summary NPIs • Nonpharmaceutical interventions (NPIs) likely to be

effective in mitigating influenza pandemic

– Effectiveness unknown, will depend on implementation and compliance with interventions

– Multiple, early, interventions started early (targeted, layered containment) likely more effective than single intervention

– May be the only interventions available early in pandemic

– Consequences of interventions need to be considered

– Additional research needed

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Challenges, Spring, 2009• April, 2009: Early emergence of H1N1 in US, lack of

data on severity (suggestion from Mexico early of “moderate-high” severity) resulted in:

– Need for national school closure surveillance system– Need to develop/implement NPI policies with

insufficient data– School closure guidance/policies that deviated from

USG planning and required modifications with additional data

– Need to develop other/unanticipated NPI guidance: Public/mass gatherings, Post-Secondary Schools, Correctional Facilities, Summer Camp, Child Care, Other

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School Closure Surveillance, Spring 2009

• Methods– Definition

• Public/private, K-12• Dismissal/Closure >= 1 day• Attributed/associated novel influenza A or ILI

– April 27 – June 12, 2009– Media + state/local education website reviews– Direct reports to CDC, DOEd– Confirmation with district

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School Closures, Spring 2009

• Results: April 27 – June 12– 35 States and DC >= 1 school– 1351 (1%) schools dismissed/closed >= 1

day• Mean 3.8 days (range 1 – 9 days)• 5137 total days of school lost

– 824,000 students affected (3,170,000 student-days school lost)

QuarantineTM13Source: ED and CDC Confirmed School Closing Reports released each weekday at 2:00pm

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Number of school and student dismissals related to novel influenza A (H1N1), United States,

April 27 – June 12, 2009

May 5 - School dismissal

not recommended

May 1 - School dismissal

recommended for 14 days

Apr 27 - School dismissal

recommended for 7 days

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Schools Closed

Students Affected

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Schools Closed

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June 17 – Endedschool dismissal

surveillance

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Observations

• Schools Responsive to CDC Recommendations– Pre-emptive dismissal/closure rarely employed – Sporadic– Impact on disease?

• Severity: Pandemic Severity Index (PSI): 2 or less– High Risk Persons at risk for hospitalization and death (eg

Asthma)

• Transmission: < seasonal influenza– Highest in school age– Maybe some protection with older age– Predominant modes: contact vs. droplet vs. air?

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ESSENCE: Total ILI and ILI among 5-17 year olds, Counties A and B, 2009

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1/1/09 1/29/09 2/26/09 3/26/09 4/23/09 5/21/09

ILI

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County A County A age 5-17 County B County B age 5-17

* Influenza-like illness, chief complaint of emergency department visits reported to ESSENCE

Spring break H1N1 school closureWinter break(County A)

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Proportion of 5-17 year olds with ILI: comparison when schools open or closed,

Counties A and B, Jan – June 2009

50%50%School Open

75% 25%School Closed

Other Ages5 – 17

year olds

RR= 0.5 95% CI: [0.47, 0.53] p=.0001

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Ongoing NPI Studies (CDC)

• School Closure/Dismissal & Other– Effectiveness – KAB including Adherence to Recommendations

• Ill students/teachers stay home• Quarantine• Re-congregation • Hygiene

• Consequences of School Closure– economic and other

• Other & Community NPIs– Social Distancing

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Next Steps• Goals of interventions

– Reduce Morbidity and Mortality– Minimize Social Disruption

• Effectiveness of School Closure/Dismissal (Spring and Summer)– Review Spring experience (descriptive epidemiology)– Summer Camp experience– International experience

• Establish Surveillance & Monitoring for Fall– School dismissal/closure– Other– Real-time evaluation and feedback

• Effectiveness of NPIs – Isolation, Quarantine, Social Distancing (including School

Closure/Dismissal), Hygiene, PPE