RSV (Respiratory Syncytial Virus)

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.

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.

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.

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.

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.