Did you get sick last winter with flu-like symptoms such as a runny nose and headaches? It could have been respiratory syncytial virus (RSV), a common winter virus affecting both children and adults.

Viral shedding refers to how a virus can exit our body, like when we talk or cough. When this happens, there’s a chance that we can infect someone else, even if we don’t show symptoms.^1,2,3 The amount of time a person spends shedding a virus depends on factors such as age. Typically, adults shed less RSV than children, and for a shorter period of time.⁴ Studies suggest that the average shedding time for this group is 1-2 weeks.^3,5 However, in immunocompromised adults, this can take far longer, up to 168 days.^1,6,7

What is RSV?

It is one of the most common viruses affecting the human population, with most people being infected at least once by age two. It’s passed from one person to another by close contact, like shaking hands with an infected person. It can also be transmitted by droplets and bodily fluids. The disease can live on surfaces such as counters for 4-7 hours. The incubation period (time between the virus entering the body and symptoms showing) is 3-5 days. 

This disease appears every year in the UK and other temperate climates, with peak infection occurring during December. This may be because cold weather increases our susceptibility to infection.⁸ It’s also been suggested that people gathering indoors to avoid the cold might make it easier to spread the virus.² Once in the body, this disease affects the upper respiratory tract and may spread to the lower tract to cause bronchiolitis or pneumonia. However, this rarely occurs in adults, making it more difficult to diagnose precisely. 

Symptoms

Some symptoms experienced by adults may include:

• Cough
• Congested and/or runny nose
• Sneezing
• Croup
• Ear infections
• Fever
• Fatigue
• Lack of appetite

Risk factors

In typical adults, this usually presents as a mild illness, with flu-like symptoms. It’s also possible to be infected with RSV and be asymptomatic. However, some risk factors may increase the chances of a severe infection. These include:

• COPD
• Cardiopulmonary and cardiovascular disease
• Smoking or being around someone who smokes
• Being admitted to a hospital during the peak of RSV season
• Having a compromised immune system
• Vitamin D deficiency²

How do we become infected?

The virus can bind receptors on the surface of our cells, and two surface proteins, G and F, play a key role in this process. RSV is classified into the A and B types based on the type of G protein it contains. The G protein helps the virus to attach to the human host cell, while the F protein allows the protein coating the virus to attach to the membrane of the human cell. 

Once this is done, the virus can enter the cell. The virus can then use the genetic material within our cells (DNA and RNA) to produce thousands of copies of itself. This results in the cell bursting, releasing these viral particles throughout the body. These can be expelled using the same routes that the virus entered the body, enabling shedding to occur.⁹

A study in 2019 suggests that RSV might interfere with the body’s immune response, meaning you can get re-infected throughout your life.¹⁰ However, being infected may help reduce the severity of future infections.¹¹

RSV shedding in adults

It’s important to understand how long shedding occurs, as this determines how long you may be infectious and what measures you can take to prevent disease transmission. Shedding duration depends on factors like intensity of infection, age, and whether you are symptomatic.^1,3 In a 2014 study, the average time for a person over 15 to shed RSV was 9 days, with people presenting symptoms taking twice as long as those who didn’t. 

Many studies have also looked at the viral shedding periods for immunocompromised patients, including those who have received a transplant or have cancer. They are particularly susceptible to severe infection due to:

• Being inside hospitals, where RSV outbreaks can occur
• A reduced immune system (due to treatment and/or disease) makes the body more susceptible to other infections

A study from the COVID-19 pandemic in France found asymptomatic patients shed RSV longer, without a difference between RSV-A and RSV-B infections.¹ However, research in Germany found a slight difference in shedding times: 18.5 days for RSV-A and 25.5 days for RSV-B.⁷

RSV shedding can begin 1-2 days after symptoms appear and decrease after 5-6 days.⁵ Hospitalised patients were observed to shed for nearly 2 weeks, while those managing symptoms at home shed for around 10 days.⁵ In patients with blood cancer, shedding can range from 5 to 50 days.⁶

How do we detect shedding?

Because of how mild RSV cases tend to be in the adult population, many cases go undiagnosed. However, in serious cases, a nose and throat swab may be taken for lab diagnostics. These may include tissue culture or PCR.

Tissue culture

This approach involves isolating the virus from the provided sample and infecting suitable cells in the lab. RSV causes the infected cells to burst, forming clear areas called plaques on the Petri dish. By counting these plaques and considering the dilution levels of the virus, we can estimate the amount of virus being shed. However, tissue culture may not be very sensitive in adults, as they generally shed less virus.⁴

PCR

This technique is far more sensitive, as it involves increasing the number of desired viral genetic material in a series of cycles. Once this has been done, we can compare the fluorescence signal from the sample to a calibration standard and determine how much viral RNA (in this case) is present. However, not all RSV particles in the body necessarily cause infection. One disadvantage of this method is that it can’t tell the difference between the RNA from an RSV particle that can cause infection, versus that from a particle which does not cause infection.

Treatment and prevention

Most cases of RSV can be managed at home, as they present similar to a cold or flu. Over-the-counter medications may help alleviate some of the symptoms, although they are not a cure for the disease. To prevent spreading the virus, you can take the following steps:

• Wash hands regularly using warm water and soap for at least 30 seconds
• Cover all coughs and sneezes with your elbow 
• Clean surfaces which you have come in contact with regularly, and avoid touching surfaces such as public stair and escalator railings
• To prevent serious infection in infants, symptomatic individuals should avoid contact with newborns, premature infants, and children under two with heart or lung issues

In severe cases, the antiviral ribavirin may be used. However, we don’t fully understand its efficacy.² It has been suggested that starting ribavirin treatment earlier during infection increases its efficacy, compared to when used later on.²

Vaccine

Two vaccines, Abrysvo and Arexy, have been developed to protect against RSV. These are both one dose and can be used in those aged 60 and above.

Abrysvo

This is available in the UK on a prescription basis and is also available to those who are pregnant. This vaccine has been developed by Pfizer and contains the F surface proteins from both RSV-A and RSV-B. Once this vaccine has been administered, the body begins to produce an immune response against the F proteins. If the body later encounters RSV, it can recognise and respond to the virus, helping to prevent serious illness. Side effects include:

• Muscle aches
• Tiredness
• Headache
• Pain where the injection was given

Arexvy

This is another prescription-only vaccine and is only suitable for those aged 60 and above. Unlike Abrysvo, this uses the F protein mixed with an adjuvant, which helps the immune system generate helper T cells that recognise the surface protein. When the body comes across RSV again, the immune system should be able to fight the infection effectively. This vaccine is effective against RSV-A and RSV-B. Side effects include:

• Headache
• Muscle aches
• Fatigue
• Pain in joints

Summary

RSV is a common virus affecting the respiratory tract, especially in young children and vulnerable adults. It spreads through close contact and respiratory droplets, with peak infection in winter. Symptoms include cough, congestion, and fever, but the virus can cause bronchiolitis and pneumonia in high-risk groups.

Adults typically shed the virus for 1-2 weeks, but this can take longer in the immunocompromised. Detection involves tissue culture or more sensitive PCR tests. To prevent infection, good hygiene practices should be observed. Treatment mainly requires symptom management, though severe cases may use the antiviral ribavirin. Vaccines have also been developed for those over 60 to prevent serious illness.