Respiratory Syncytial Virus

Background

The Respiratory Syncytial Virus (RSV) was first identified in chimpanzees in 1956, and then identified as . It wouldn’t be until 1981 that a better understanding of the virus was achieved through genetic sequencing of the virus. That advancement led to a leap in research into a vaccine against the disease it causes.

According to the Centers for Disease Control and Prevention (CDC), infections with RSV can cause as many as “2.1 million outpatient visits (non-hospitalization) visits among children younger than 5 years old;” “60,000 to 160,000 hospitalizations among adults 65 years and older;” “6,000 to 10,000 deaths among adults 65 years and older;” and “100-300 deaths in children younger than 5 years old.”

Currently, there are . The CDC compiles the information from those networks in . As of 2023, the latest report notes that “RSV circulation was historically low during 2020–21, and began earlier and continued longer during 2021–22 than during pre-pandemic seasons. The 2022–23 season started later than the 2021–22 season, but earlier than pre-pandemic seasons, suggesting a return toward pre-pandemic seasonality.”

Symptoms and Causative Agent

, the symptoms of RSV disease include:

• Runny nose
• Decreased appetite
• Coughing
• Sneezing
• Fever
• Wheezing

RSV is an RNA virus from the family of viruses in the genus. The virus has two subgroups: A and B. There are also RSV strains that cause infection in cows, sheep, and mice. Genetically, RSV is a close relative of other respiratory viruses like human metapneumovirus, parainfluenza, and measles.

According to Collins et al., cited below, virus particles measure between 100 and 350 nanometers (billionths of a meter) that can exist as filaments 60 to 200 nanometers in diameter and 10 nanometers long. Like other viruses, RSV enters the cell and sheds its protein coat. Its RNA (genetic material) is then copied into a corresponding messenger RNA (mRNA) strand. The host cell machinery then takes up that mRNA to produce virus proteins that are then assembled into new virus particles. After enough virus particles are created, the cell develops “surface projections” and binds to other cells. These bound cells are known as syncytia, which gives the virus its name.

The immune system reacts to syncytial cells by destroying them, or they are destroyed during viral replication. It is this destruction and immune response that cause symptoms. When the cells and tissues are damaged enough, the condition can be life-threatening.

Transmission

Transmission of RSV occurs through . This can happen when an infected person coughs, sneezes, or talks, releasing tiny droplets into the air that can be inhaled by others. The virus can also be spread by touching a surface contaminated with the virus, and then touching one's nose, mouth, or eyes.

As with other respiratory pathogens, hand washing helps prevent infection with RSV. People infected with RSV should cover their coughs and sneezes, and avoid close contact with people who are not infected. It is especially important to take precautions around people at high risk of severe disease from RSV, like the young, the old, and those with preexisting medical conditions.

Treatment and Care

There is no specific treatment for RSV, only supportive treatment to manage symptoms and complications.

Complications

The most severe is death due to respiratory failure. If the infection is deep within the lungs, bronchiolitis and pneumonia may develop. (According to CDC, RSV is the “most common cause of bronchiolitis and pneumonia in children younger than 1 year of age.”) In older adults, RSV can cause severe respiratory disease that requires oxygen or . If the condition is severe enough, may be necessary to assist in breathing. However, most hospitalized cases recover quickly.

Available Vaccines

On May 3, 2023, the Food and Drug Administration (FDA) . The results of a clinical trial of the vaccine were . In , FDA stated it “is requiring the company to conduct a postmarketing study to assess the signals of serious risks for Guillain-Barré syndrome and ADEM. In addition, although not an FDA requirement, the company has committed to assess atrial fibrillation in the postmarketing study.” 

The .The vaccine will be included in the .

Resources and Additional Readings

• Morris, J. A., R. E. Blount Jr, and RE13359460 Savage. "Recovery of cytopathogenic agent from chimpanzees with goryza." Proceedings of the Society for Experimental Biology and Medicine 92.3 (1956): 544-549.
• ROBERT CHANOCK, BERNARD ROIZMAN, RUTH MYERS, RECOVERY FROM INFANTS WITH RESPIRATORY ILLNESS OF A VIRUS RELATED TO CHIMPANZEE CORYZA AGENT (CCA): ISOLATION, PROPERTIES AND CHARACTERIZATION, American Journal of Epidemiology, Volume 66, Issue 3, November 1957, Pages 281–290, 
• Papi, Alberto, et al. “Respiratory Syncytial Virus Prefusion F Protein Vaccine in Older Adults.” NEW ENGLAND JOURNAL OF MEDICINE, vol. 388, no. 7, Massachusetts Medical Society, 2023, pp. 595–608, doi:10.1056/nejmoa2209604.
• Collins PL, Fearns R, Graham BS. Respiratory syncytial virus: virology, reverse genetics, and pathogenesis of disease. Curr Top Microbiol Immunol. 2013;372:3-38. doi:10.1007/978-3-642-38919-1_1