Respiratory syncytial virus (RSV): symptoms, transmission, prevention, treatment

Updated 16 September 2021

Respiratory syncytial virus (RSV) is an enveloped RNA virus, in the same family as the human parainfluenza viruses and mumps and measles viruses. RSV is one of the common viruses that cause coughs and colds in winter.


RSV is transmitted by large droplets and by secretions from contact with an infected person. The virus can survive on surfaces or objects for about 4 to 7 hours.

The incubation period - the delay between infection and the appearance of symptoms - is short at about 3 to 5 days.

When RSV circulates

In temperate climates such as the UK, RSV occurs regularly each year. Epidemics generally start in October and last for 4 to 5 months, peaking in December. The sharp winter peak varies little in timing or magnitude, in contrast to influenza virus infection which is much less predictable in its timing.

Risks of RSV infections

For most people, RSV infection causes a mild respiratory illness. For a small number of people who are at risk of more severe respiratory disease, RSV infection might cause pneumonia or even death.

RSV is the most common cause of bronchiolitis in infants. Over 60% of children have been infected by their first birthday, and over 80% by 2 years of age. The antibodies that develop following early childhood infection do not prevent further RSV infections throughout life. The full extent to which adults are affected by RSV remains unknown.

The NHS website has more information on RSV bronchiolitis and when to seek help.

High-risk groups

The very young (under 1 year of age) and the elderly are at the greatest risk. While most RSV infections usually cause mild illness, infants aged less than 6 months frequently develop the most severe disease such as bronchiolitis and pneumonia, which may result in hospitalisation. Children born prematurely, or with underlying chronic lung disease, and the elderly with chronic disease are also at increased risk of developing severe disease.

Only a minority of adult infections are diagnosed, as RSV is not widely recognised as a cause of respiratory infections in adults. Elderly patients are frequently not investigated microbiologically, as there are fewer viruses present in their respiratory secretions compared with children. This results in the number of adult infections being underestimated.

Symptoms and diagnosis

RSV infection causes symptoms similar to a cold, including rhinitis (runny nose, sneezing or nasal congestion), cough, and sometimes fever. Ear infections and croup (a barking cough caused by inflammation of the upper airways) can also occur in children. RSV is the leading cause of bronchiolitis, an infection of the small airways in the lung, in babies and infants which make breathing harder and cause difficulty feeding.

During the RSV season a laboratory diagnosis is not always necessary as infection can be managed. Specific laboratory tests to confirm RSV require a sample to be taken from the nose and throat.

The Respiratory virus unit (RVU) provides laboratory services for respiratory virus infections including RSV.


There’s no specific treatment suitable for general use, and treatment is therefore aimed at supporting the patient and relieving symptoms. Ribavirin is an anti-viral drug licensed for treatment of RSV infection which is sometimes used in the management of severe illness. Its effectiveness is not established, and it may be associated with toxicity.


Transmission can be reduced through standard infection control practices such as respiratory hygiene, hand washing with soap and warm water, and cleaning of surfaces. Ideally, people with colds should avoid close contact with newborn babies, infants born prematurely (before 37 weeks), children under 2 born with heart or lung conditions, and those with weakened immune systems. Smoking around young children is a risk factor for severe RSV infection.


See the chapter about RSV immunisation in Immunisation against infectious disease: the Green Book.

Palivizumab, a monclonal antibody therapy, is licensed in the UK for the prevention of serious lower respiratory tract infection caused by RSV in infants at high risk of infection.

Human metapneumovirus

Human metapneumovirus (hMPV) is a respiratory pathogen closely related to RSV. It is associated with a range of illnesses from mild infection to severe bronchiolitis and pneumonia. Symptoms may include a runny nose, cough, temperature, sore throat, and wheezing. Like RSV, hMPV is thought to be a seasonal virus occurring mostly during the winter months. However, the number of people which suffer from hMPV each year is still to be determined.

HMPV infection occurs in infants and young children with studies suggesting that nearly everyone has had hMPV infection by the age of 5 years old. However, hMPV has also been found in older children and adults suggesting re-infection may occur later on in life.

UK Health Security Agency (UKHSA) activity

Information about levels of RSV activity in the UK is reported by the UKHSA throughout the winter period.

Read the latest respiratory reports.