To find out if respiratory syncytial virus (RSV) is causing the respiratory symptoms of the person, particularly children, elderly people and those who are immunocompromised. The test can also help to let healthcare professionals know whether the RSV season has started.
RSV (Respiratory Syncytial Virus)
When someone is experiencing runny nose, sneezing, coughing along with a raised temperature and /or difficulty in breathing and RSV is suspected. The RSV season is usually late autumn to early spring (November to March in the Northern Hemisphere), but people can be infected at any time of the year.
No test preparation is needed
RSV testing is used to detect respiratory syncytial virus, a common viral respiratory infection. RSV tends to be seasonal, causing community epidemics in young children, older adults, and immunocompromised patients. In these high-risk groups, RSV can cause deep seated lung infections such as pneumonia and bronchiolitis (inflammation of the small airways in the lungs). Affected people may have symptoms such as severe coughing, difficulty breathing, and high fevers. The season usually begins in the late autumn and continues into the spring. This would be late November through to the end of March in the Northern Hemisphere. (Note that the usual seasonal pattern was disrupted in 2020 and 2021 due to the lockdowns used to reduce the spread of COVID-19).
RSV testing detects virus that is being shed in the respiratory/nasal secretions of an infected person. Since detectable amounts of virus are usually only shed for the first few days of an infection, most testing must be done during this time period. There are several methods to test for the virus. There is a rapid ‘lateral flow’ test, which can be carried out by staff on the ward. This looks for virus particles in the sample and is quick and easy to do. A result would usually be ready within 30 minutes to an hour.
When the patient has symptoms suggesting RSV infection, but the rapid lateral flow test is negative, a sample might be sent to the laboratory for further investigations. The main laboratory test looks for the genetic code of the virus and it is better at picking up the virus when it is present in smaller amounts. The other advantage of sending the sample to the laboratory, is that the tests there are usually set up to test for other common respiratory viruses. That extra information can be very useful because someone might have similar symptoms but be infected with a different virus. The results from these types of test will usually be available on the same day that the sample was collected.
Not every hospital has a specialised virology laboratory to do these more detailed tests for the RSV genetic code, so the samples from patients who need this test might have to be sent to a laboratory at a different site. However, there are now machines which are effectively mini-laboratories which can do the genetic code testing, but which are small enough to fit on a table. Some hospitals are starting to use those to test for some viruses including RSV.
How is it used?
RSV testing is usually used during the RSV season to help diagnose patients who have moderate to severe symptoms and lower respiratory tract involvement. It is primarily requested on infants (between the ages of 6 months and 2 years), elderly patients, and those with compromised immune systems, such as those who have pre-existing lung disease or who have had an organ transplant. Older children and the rest of the general population are not routinely diagnosed or tested because most of them will experience only relatively mild upper respiratory infections with symptoms such as a runny nose, sneezing, coughing, sore throat, and fever. RSV testing is also used to document and track the spread of RSV in the community. Since most cases of RSV are self-limiting, community health efforts are focused on containing and preventing the spread of RSV as much as possible to minimize the chance of spreading the virus to high-risk patients. Treatment of RSV is primarily supportive, minimizing pain and fever and easing breathing. Those with mild symptoms may only be tested for RSV if it is necessary to help track its spread. RSV testing is frequently requested along with influenza testing if both viruses are known to be present in the community. These tests are used to detect the presence of RSV or influenza and to evaluate the likelihood that an individual patient’s symptoms may be due to one of these viruses or to another cause, such as a bacterial infection.
When is it requested?
RSV tests are requested almost during “cold and flu season” – late autumn to early spring or when there is a possible outbreak of this infection. They are requested when a patient, usually an infant or elderly person, complains with a lower respiratory infection and symptoms such as wheezing, severe coughing, rapid breathing (primarily in infants), fevers, headaches, a runny stuffy nose, and a sore throat. When RSV has already been identified in the community, the doctor may request a rapid RSV test to confirm the suspected diagnosis in the symptomatic patient. If influenza is also in the community, RSV testing may be requested along with influenza testing to determine which virus the patient has. The doctor may also order bacterial tests, such as a send a throat swab for bacterial culture (to check for group A streptococcus, the bacteria that cause streptococcal sore throat), when the cause of the infection is unclear.
What does the test result mean?
If a rapid RSV test is positive, then it is likely that the patient has respiratory syncytial virus. A positive viral culture or genetic viral test can confirm the presence of RSV in the community. A positive RSV test cannot, however, tell a doctor how severe a patient’s symptoms are likely to be or how long ago they were infected. Symptoms usually appear 4-6 days after infection. Negative rapid RSV tests may mean that you have something other than RSV or that there is not sufficient virus in the specimen to allow it to be detected. This may be due to either a poor specimen collection or because you are not shedding detectible levels of virus into your respiratory secretions. Adults tend to shed less virus than infants do, and those who have had RSV for several days will shed less than those with a more recent infection.
Is there anything else I should know?
Most RSV infections will go away within 1 or 2 weeks. People can be re-infected with different strains of RSV from year to year, although subsequent infections tend to be less severe than the first/primary infection. Since most RSV infections are mild, symptoms from these re-infections are usually attributed to “a cold.” These cases of RSV are usually not formally diagnosed and are often treated by the patient with over-the-counter cold remedies for symptom relief.
Is there a blood test for RSV?
There are blood tests for RSV antibodies – the immune system’s response to the virus. These tests can detect previous exposure to RSV, but they are not usually considered clinically useful for diagnosing an active case of RSV.
Is there a vaccine like the 'flu' shot to prevent RSV?
Are antibiotics useful when I have RSV?
No, RSV is due to a virus – not a bacteria – so antibiotic therapy is not indicated or helpful. There are some antiviral treatments available to treat RSV infection, but they are usually only needed for high risk patients. There are several antiviral drugs which and an immunotherapy treatment. These drugs do not prevent or cure RSV infection, but minimize lower respiratory tract involvement, reducing the need for hospitalization in affected patients. Immunotherapy may be given to neonates in the intensive care nursery to protect them during RSV season. Premature infants can be especially vulnerable to RSV.
Elsewhere On The Web
Public Health England, Guidance Respiratory syncytial virus (RSV): symptoms, transmission, prevention, treatment
MedlinePlus Health Information, Medical Encyclopedia: Respiratory syncytial virus
March of Dimes: Respiratory Syncytial Virus (RSV)
KidsHealth for Parents: Respiratory Syncytial Virus