What is the History of Respiratory Syncytial Virus (RSV) infection in the U.S. and other countries?

Respiratory Syncytial Virus (RSV) was initially identified in 1955 by JA Morris in laboratory chimpanzees housed at Walter Reed Army Institute of Research in Maryland.¹ The chimpanzees, which were used in polio vaccine research, exhibited symptoms of respiratory illness.² Morris was able to confirm that the viral agent, which was initially named Chimpanzee Coryza Agent (CCA), was contagious when he exposed a second group of chimpanzees to the infection.³

In February 1956, a laboratory worker was purposely exposed to the infected chimpanzees and developed symptoms that included a low-grade fever, runny nose, cough, and headache. The lab worker initially tested negative for antibodies, but positive two weeks later. Additionally, blood samples taken from young adults living near Walter Reed Army Medical Center but most infants and children were negative. Antibodies, however, were detected in young adults, of which eight were dwelling in the same army barracks as the initial laboratory worker.⁴

Robert Chanock, a pediatrician and virologist, from Johns Hopkins University began research to isolate a novel pathogen believed to be causing severe respiratory illness in infants While researching, Chanock discovered two additional agents in babies with croup and pneumonia that were identical to CCA.⁵ Johns Hopkins is located within a 30-mile radius of Walter Reed Army Institute, where CCA was initially identified.

Due to the similarity of the novel pathogens to CCA and its characteristics, Chanock suggested the virus be renamed “Respiratory Syncytial” virus.⁶ In 1960, the virus was found in over 50 percent of the young babies diagnosed with pneumonia or bronchiolitis in the Washington D.C. area and in 12 percent of older infants and young children and labeled as a “respiratory pathogen of major significance during early life”.⁷ By the early 1960s, the virus was identified in Australia and attributed to an epidemic of lower respiratory illness in infants.^{8 9}

By the early 1980s, RSV was considered the most significant lower respiratory infection in infants and children under the age of two, with most presenting with bronchiolitis and pneumonia. Most outbreaks were reported in the late fall and spring in the U.S. and lasted between two and five months.¹⁰

Public health officials report that between four and five million children develop RSV infection each year, ¹¹ with approximately 2.1 million resulting in outpatient treatment, between 58,000 and 80,000 requiring hospitalization, and between 100 and 300 deaths. Additionally, the virus is estimated to be responsible for between 60,000 and 120,000 hospitalizations and between 6,000 and 10,000 deaths in adults 65 years of age and older.¹²

Prior to 2020, the seasonality of RSV was well established in the U.S., with the season onset ranging from mid-September to mid-November, with the peak from late December to mid-February, and the off-set concluding in mid-May. Since 2020, however, there has been a shift in RSV infection patterns, with the southern U.S. experiencing an increase in cases in the spring and peaking in July. Health officials attribute the change in RSV patterns to disruptions from the COVID-19 pandemic.

Globally, researchers report that in 2019, there were an estimated 33 million lower respiratory infections associated with RSV, 3.6 million RSV hospitalizations, and 26,300 in hospital deaths related to RSV. Additionally, researchers estimated that approximately 101,400 RSV-associated deaths also occurred in children under the age of five years.¹³

IMPORTANT NOTE: NVIC encourages you to become fully informed about Respiratory Syncytial Virus (RSV) and the Respiratory Syncytial Virus (RSV) vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.

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