Understanding Viral Shedding in RSV

Author: Sanofi

Editorial Team

Viral shedding involves the release of infectious virions (virus particles) from an infected host into the environment, facilitating transmission to new hosts. Viral shedding is crucial for maintaining infections within populations.¹ In this article, we’ll be exploring viral shedding in the context of respiratory syncytial virus (RSV) infection.

How does viral shedding work?

The first step of viral shedding is when the virus enters the body and infects host cells.¹ The virus particles are then released from the infected cells primarily via budding, exocytosis, or cell death.^2,3

For example, RSV virions undergo budding. After replication, RSV virions are assembled near the plasma membrane, where F proteins may bind and attract M proteins, starting filament budding. Filament formation may also begin inside the cell, with vesicles developing into filaments and loading with nucleocapsids before fusing with the plasma membrane.^4,5 This process leads to the release of new viral particles from various cellular membranes.^5,6

These newly released virions may either infect other healthy cells or be dispersed into the environment through actions such as coughing, sneezing, or other similar occurrences that infect healthy individuals.⁶

Keep learning about RSV pathophysiology

Viral shedding signs and symptoms

Symptoms of viral shedding usually refer to those associated with the underlying condition, such as in RSV.⁷

For example, symptoms of RSV normally appear from Day 3 through to Day 8 and can include coughing and runny nose. This is typically the time around which viral shedding could potentially occur.^8,9

Asymptomatic viral shedding can also occur, which is when the virus is present in the absence of clinical signs or symptoms.¹⁰

Viral shedding and transmission

Viral shedding and contagion are closely intertwined. People with a viral infection are most contagious during the peak shedding period. This increases the risk of viral transmission, especially in close-contact environments such as daycare centers and healthcare facilities.^10,11

Persistent or prolonged viral shedding may increase the possibility of transmission.^1,7

For example, prolonged shedding of RSV not only enhances the possibility of RSV transmission but also makes these individuals potential vectors for community-wide infection. These factors underscore the importance of considering prolonged viral shedding in the management and prevention of RSV infection and its impact on infants.⁷

About RSV transmission and incubation

How long does viral shedding last?

The duration of viral shedding varies depending on the type of virus, the host, and whether the patient is symptomatic or asymptomatic.⁶

For example, adults will shed RSV for 3 to 7 days following the infection, while infants generally shed for up to 14 days in mild infections, although this could be as long as 3 weeks in infants with severe infection and several months for those who are immunocompromised.⁶

The duration of RSV viral shedding is estimated to be longer in symptomatic individuals compared with asymptomatic individuals, approximately 13 days versus 7 days, respectively.¹⁰

How to reduce viral shedding and prevent disease spread

An understanding of viral shedding kinetics and changes in infection risk over time could inform prevention of disease spread.¹²

The change in viral shedding from the estimated time of infection, together with the risk of transmission in the household setting, shows that the initial week after the exposure to an RSV case is important for preventing RSV transmission.¹²

Read more on how to prevent the transmission of RSV or keep learning about RSV pathophysiology.

Frequently asked questions

When does viral shedding occur?

Where does viral shedding occur?

What is viral load vs viral shedding?

Does viral shedding decrease over time?

References

1. Louten J. Virus transmission and epidemiology. Essential Human Virology. 1st ed. Academic Press; 2016:71-92. 2. Ryu WS. Virus life cycle. Molecular Virology of Human Pathogenic Viruses. Academic Press; 2017:31-45. 3. Payne S. Virus interactions with the cell. Viruses. 1st ed. Academic Press; 2017:23-35. 4. Förster A, Maertens GN, Farrell PJ, Bajorek M. Dimerization of matrix protein is required for budding of respiratory syncytial virus. J Virol. 2015;89(8):4624-4635. 5. Battles MB, McLellan JS. Respiratory syncytial virus entry and how to block it. Nat Rev Microbiol. 2019;17(4):233-245. 6. Kaler J, Hussain A, Patel K, Hernandez T, Ray S. Respiratory syncytial virus: A comprehensive review of transmission, pathophysiology, and manifestation. Cureus. 2023;15(3):e36342. 7. Okiro EA, White LJ, Ngama M, Cane PA, Medley GF, Nokes DJ. Duration of shedding of respiratory syncytial virus in a community study of Kenyan children. BMC Infect Dis. 2010;10:15. 8. Symptoms and care of RSV. Centers for Disease Control and Prevention. August 30, 2024. Accessed December 10, 2024. https://www.cdc.gov/rsv/symptoms/index.html 9. Eiland LS. Respiratory syncytial virus: diagnosis, treatment and prevention. J Pediatr Pharmacol Ther. 2009;14(2):75-85. 10. Munywoki PK, Koech DC, Agoti CN, Bett A, Cane PA, Medley GF, et al. Frequent asymptomatic respiratory syncytial virus infections during an epidemic in a rural Kenyan household cohort. J Infect Dis. 2015;212(11):1711-1718. 11. Barker J, Stevens D, Bloomfield SF. Spread and prevention of some common viral infections in community facilities and domestic homes. J Appl Microbiol. 2001;91(1):7-21. 12. Otomaru H, Sornillo JBT, Kamigaki T, et al. Risk of transmission and viral shedding from the time of infection for respiratory syncytial virus in households. Am J Epidemiol. 2021;190(12):2536-2543. 13. Zhang L, Peeples ME, Boucher RC, Collins PL, Pickles RJ. Respiratory syncytial virus infection of human airway epithelial cells is polarized, specific to ciliated cells, and without obvious cytopathology. J Virol. 2002;76(11):5654-5666. 14. DeVincenzo JP, Wilkinson T, Vaishnaw A, et al. Viral load drives disease in humans experimentally infected with respiratory syncytial virus. Am J Respir Crit Care Med. 2010;182(10):1305-1314. 15. Walsh EE, Peterson DR, Kalkanoglu AE, Lee FEH, Falsey AR. Viral shedding and immune responses to respiratory syncytial virus infection in older adults. J Infect Dis. 2013;207(9):1424-1432.

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