RSV (Respiratory Syncytial Virus)
When it is RSV season (late autumn until early spring) and your doctor wants to determine whether your runny nose, congestion, coughing and/or difficulty breathing are due to RSV or to other causes
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 that typically begin in November or December and disappear in early spring. In these high-risk groups, RSV can cause pneumonia and bronchiolitis. Affected patients may have symptoms such as severe coughing, difficulty breathing, and high fevers.
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, but rapid RSV antigen testing is by far the most popular. Rapid RSV antigen tests are frequently performed on-site, in the doctor’s office or the emergency room, with most results available within an hour. In some cases, the sample may be collected and sent to a laboratory for a more sensitive testing method. Results of these RSV tests are usually available the same day.
Occasionally, samples will be sent to detect the virus’s genetic material. These tests have the advantage of identifying not only the RSV virus but also other respiratory viruses that may be present. The main disadvantages of these tests are that they are not available in every laboratory and that the results take longer than the rapid RSV test. This makes them less clinically useful for evaluating an individual patient, but they can be useful for documenting that RSV or another virus, such as influenza, has reached a community and for identifying outbreaks in particular populations, such as a nursing home, school, or neighbourhood.
How is the sample collected for testing?
Sample collection technique is critical in RSV testing. The best and most frequently used sample is a nasopharyngeal aspirate. Gentle suction is applied via a nostril to obtain the aspirate.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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 exclusively during “cold and flu season” – late autumn to early spring. 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?
Not currently, although it is considered a high priority by researchers.
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 is a short-term drug therapy that is given to some high-risk patients. It does not prevent or cure RSV infection, but it minimizes lower respiratory tract involvement, reducing the need for hospitalization in affected patients. This 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
Health Protection Agency (Respiratory syncytial virus)
CDC, National Center for Infectious Diseases: Respiratory Syncytial Virus
MedlinePlus Health Information, Medical Encyclopedia: Respiratory syncytial virus
March of Dimes: Respiratory Syncytial Virus (RSV)
KidsHealth for Parents: Respiratory Syncytial Virus
American Academy of Pediatrics: RSV, When It’s More Than Just a Cold