Brian Rha, MD, MSPH Medical Epidemiologist, Division of Viral Diseases

Centers for Disease Control and Prevention

Severe Acute Respiratory Infection Surveillance in the Americas (SARInet) Meeting

Cancun, Mexico

28–30 April 2015

Estimating RSV Disease Burden in the United States

National Center for Immunization and Respiratory Diseases

Division of Viral Diseases

Respiratory Syncytial Virus (RSV)

Common cause of acute respiratory infections • Most infected in 1st year of life

• Virtually all children infected by 2 years of age

• Repeat infections affect older children and adults

Most common cause of lower respiratory tract infections among infants • Manifests as bronchiolitis or pneumonia

Diagnosis using rapid tests of respiratory specimens • Antigen assays

• Reverse transcriptase-polymerase chain reaction (RT-PCR) assays

Clinical Manifestations – Primary Infection

Most have upper respiratory tract symptoms

20–30% develop lower respiratory tract disease • Bronchiolitis and/or pneumonia

• Most do not require hospitalization

• Symptoms: tachypnea, cough, labored breathing, wheezing, crackles

Fever may be absent

Young infants may present with apnea, irritability, poor feeding

Relationship with subsequent development of recurrent wheezing unclear

* http://sites.path.org/vaccinedevelopment/files/2011/12/RSV-snapshot-March2015.pdf

Approaches to Estimating RSV Hospitalization Burden

Retrospective analysis of national hospitalization data

• Hospital discharge data from national survey/insurance databases

• Estimates often rely on RSV proportions from prospective studies

Prospective active population-based surveillance

• Establishment of surveillance sites to capture cases

• Denominator data to yield rate information

• RSV diagnoses based on sensitive diagnostic tests (PCR)

Hospital Discharge Data from National Hospital Discharge Survey (NHDS) — US, 1997–2006

Discharge diagnoses codes (ICD-9-CM) • All lower respiratory tract illness (LRTI)

• Children less than 5 years of age

“RSV-associated” hospitalizations • All RSV-specific coded hospitalizations year-round

• 30% of wintertime unspecified acute bronchiolitis

• 20% of wintertime unspecified pneumonia

Average annual hospitalization rates calculated • Denominator data from US census data

• Stratified by age group

* Stockman et al. Pediatr Infect Dis J 2012; 31: 5–9

Annual Average RSV-Associated Burden by Age Group

<5 years of age: 172,000 RSV-associated hospitalizations

<1 year of age: 126,000 RSV-associated hospitalizations

(32 per 1000 infants)

* Stockman et al. Pediatr Infect Dis J 2012; 31: 5–9

New Vaccine Surveillance Network (NVSN):

Acute Respiratory Illness (ARI) Surveillance

CDC-sponsored multi-site collaborative project

Prospective surveillance for ARI in 2000–2009

Site locations in 3 US counties • Rochester, Nashville, and

Cincinnati areas

Study population: children <5 years of age

Inpatient and outpatient settings

NVSN ARI Surveillance: Hospitalized Burden of RSV

Enrollment criteria: Children <5 years of age admitted with diagnoses of acute respiratory infection* • *Illness presenting with one or more of the following symptoms: Fever,

cough, earache, nasal congestion, rhinorrhea, sore throat, vomiting after coughing, wheezing, and labor, rapid or shallow breathing

Patients interviewed, had medical records reviewed, and tested for respiratory viral pathogens • Nasal and throat swab

Hospitalization rates calculated using denominator data • US census data

• Birth certificate data

NVSN ARI Surveillance: Hospitalized Burden of RSV

Years Denominator Data Source Age group

Average annual rate of RSV-associated hospitalization

Months Rate/1000 children (95% CI)

2000–20041 US Census <60 3.0 (2.8–3.4)

0–5 16.9 (15.3–18.5)

2000–20052 Birth Certificates

<24 5.2 (4.8–5.7)

0–2 17.9 (15.7–20.1)

3–5 8.0 (6.6–9.5)

6–11 3.9 (3.2–4.7)

1. Hall et al. N Engl J Med 2009; 360: 588–98 2. Hall et al. Pediatrics 2013; 132:e341–e348

Characteristics of Hospitalized Patients (<5 Years of Age, US 2000–2004)

Variable RSV-positive

(N = 564)

%

Age <6 months 58

O2 supplementation 95

Length of stay (median days) 2

Bronchiolitis discharge diagnosis 70

High risk condition 34

Premature >1 month 16

* Hall et al. N Engl J Med 2009; 360: 588–98

Summary

RSV a significant cause of morbidity among children <5 years of age in the US • Hospitalization rates highest in young infants

Retrospective analysis of national databases can yield useful estimates

Population-based surveillance is needed for most accurate estimates of burden • Important to assess impact of case definitions

Thank You www.cdc.gov/rsv

For more information please contact Centers for Disease Control and Prevention

1600 Clifton Road NE, Atlanta, GA 30333 Telephone: 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348 Visit: www.cdc.gov | Contact CDC at: 1-800-CDC-INFO or www.cdc.gov/info

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

National Center for Immunization & Respiratory Diseases

Division of Viral Diseases