212672 An outbreak of pandemic (H1N1) influenza in an elementary school, Pennsylvania, 2009

Wednesday, November 11, 2009: 1:05 PM

Tiffany L. Marchbanks, MPH , Division of Infectious Disease Epidemiology, Pennsylvania Department of Health, Harrisburg, PA
Achuyt Bhattarai, MD , Division of Foodborne, Bacterial, and Mycotic Diseases, US Centers for Disease Control and Prevention, Atlanta, GA
Mària Moll, MD, FACP , Division of Infectious Disease Epidemiology, Pennsylvania Department of Health, Harrisburg, PA
Ryan Fagan, MD , Division of Foodborne, Bacterial, and Mycotic Diseases, US Centers for Disease Control and Prevention, Atlanta, GA
Stephen Ostroff, MD , Bureau of Epidemiology, Pennsylvania Department of Health, Harrisburg, PA
Samir Sodha, MD, MPH , Enteric Disease Epidemiology Branch, Centers for Disease Control and Prevention, Atlanta, GA
Brent Ennis, BA , Bureau of Community Health Systems, Southeast District Office, Pennsylvania Department of Health, Reading, PA
Phyllis Britz, RN, BSN , Bureau of Community Health Systems, Southeast District Office, Pennsylvania Department of Health, Reading, PA
David Swerdlow, MD , Division of Foodborne, Bacterial, and Mycotic Diseases, US Centers for Disease Control and Prevention, Atlanta, GA
Background: In May, 2009, an outbreak of 2009 pandemic H1N1 influenza occurred among elementary school A (K-4th grade) students in a semi-rural area in southeastern Pennsylvania. Rapidly increasing absenteeism among the 456 students prompted the first school closure in Pennsylvania. An investigation was conducted to assess extent of infection and patterns of transmission among students and household contacts.

Methods: A telephone survey of parents or guardians of students at School A was conducted using a standardized questionnaire to collect information on influenza-like illness (ILI) (defined as fever and a cough and/or sore throat) among students and household members. Influenza was confirmed at the Pennsylvania state public health laboratory.

Results: Among the 1157 persons in 270 (78%) households surveyed, 129 (11%) reported ILI. 37 cases were laboratory confirmed. Among the 337 School A students, 78 (23%) had ILI compared to 6% of school A household contacts (relative risk, 3.72; 95% confidence interval, 2.68 to 5.17). The proportion with ILI was highest among 4th graders (40%), with two of the four classes disproportionately affected with rates of 62% and 50%. Only 3% of ill students received antiviral treatment. Absenteeism levels returned to baseline when the school reopened after a one week closure.

Discussion: ILI was much more frequent among the School A students than their household members. Distribution of illness differed within grades at the school, and among classrooms within grades. Absenteeism returned to normal post-closure. Understanding the patterns of transmission will aid in developing prevention and control measures at schools.

Learning Objectives:
Describe transmission of Influenza A/H1N1 (novel) virus in an elementary school. Discuss school closure in response to a Influenza A/H1N1 (novel) virus outbreak.

Keywords: Infectious Diseases, Epidemiology

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I am a CDC/CSTE Applied Epidemiology Fellow assigned to the PA Department of Health. I assisted in the Influenza A/H1N1 (novel) virus outbreak investigation at the elementary school.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.

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