To help diagnose a respiratory syncytial virus (RSV) infection; to help determine whether or not RSV is circulating in your community
Respiratory Syncytial Virus (RSV) Testing
When it is RSV season (late fall through early spring in the U.S.) and an infant, an elderly person, or a person with a weakened immune system has a moderate to severe respiratory infection and symptoms such as runny nose, congestion, coughing and/or difficulty breathing
Usually a nasal aspirate or nasal wash; occasionally a nasopharyngeal (NP) swab
Respiratory syncytial virus (RSV) is a very contagious, common viral respiratory infection. RSV testing detects the presence of respiratory syncytial virus in nasal secretions to help diagnose the infection.
Most people recover from an RSV infection without any specific treatment or having to see a healthcare practitioner to get tested. However, testing may be done for infants, young children with heart or lung problems, the elderly, and people with weakened immune systems because they are particularly vulnerable. In these high-risk groups, RSV can cause pneumonia and bronchiolitis, a condition that causes inflammation of the small airways of the lungs.
Signs and symptoms of RSV infection are similar to those of other respiratory infections and usually appear 4 to 6 days after someone comes into contact with the virus. Signs and symptoms may include:
- Runny nose
- Coughing, sneezing
- Reduced appetite
- In very young infants, the only symptoms may be irritability, sluggishness (inactivity), and difficulty breathing
According to the Centers for Disease Control and Prevention (CDC), almost everyone has been infected with RSV by the time they are 2 years old. It is the most common cause of lower respiratory tract infections in young children in the U.S. and globally.
Though usually causing a mild illness, RSV can be serious in some children and adults. Each year in the U.S., RSV leads to about:
- 2.1 million outpatient visits and 57,000 hospitalizations among children younger than 5 years old
- 177,000 hospitalizations and 14,000 deaths among adults older than 65 years
The World Health Organization (WHO) estimates that globally there may be as many as 30 million RSV lower respiratory infections in children younger than 5 years old, resulting in than 3.4 million hospitalizations each year.
RSV that tends to be seasonal, causing community epidemics in the fall, winter, and spring. Outbreaks typically begin to occur in November or December and decrease by early spring.
Sample collection technique is critical in RSV testing. The best and most frequently used sample is a nasal aspirate or wash. A syringe is used to push a small amount of sterile saline into the nose, then gentle suction is applied (for the aspirate) or the resulting fluid is collected into a cup (for a wash).
Sometimes, a nasopharyngeal (NP) swab is used, although it is not preferred because the amount of virus obtained on a swab is usually low. The NP swab is collected by having a person tip his or her head back, then a Dacron swab (like a long Q-tip) is gently inserted into one of the nostrils until resistance is met (about 1 to 2 inches in), then rotated several times and withdrawn. This is not painful, but it may tickle a bit and cause the person's eyes to tear.
No test preparation is needed.
- How is it used?
Respiratory syncytial virus (RSV) testing is usually used during the RSV season to help diagnose the infection in people with moderate to severe symptoms and lower respiratory tract infection. It is primarily ordered for infants between the ages of 6 months and 2 years, the elderly, and those with weakened (compromised) immune systems, such as those who have pre-existing lung disease or who have had an organ transplant.
RSV testing is not routinely performed for older children and the rest of the general population 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 may be used to document and track the spread of RSV in the community. Public 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 people. Those with mild symptoms may only be tested for RSV if it is necessary to help track its spread. Influenza testing may also be done if both viruses are known to be present in the community.
A few types of RSV tests are available for use:
- Rapid RSV antigen testing—this is by far the most common test. Rapid RSV antigen tests are frequently performed on-site, in the healthcare practitioner'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.
- RSV RT-PCR—this is a molecular test that detects the genetic material of the virus. It is generally more sensitive than antigen testing or viral culture. It may be used in conjunction with other tests to detect other viral infections that may cause signs and symptoms similar to RSV.
- Viral cultures—these are used to grow and identify the RSV virus. Viral cultures can identify the RSV virus and other respiratory viruses that may be present. Availability of viral cultures is decreasing as most laboratories adopt molecular assays to detect viral infections. Viral cultures are costly and more difficult to perform and take days to provide a result, which makes them less clinically useful for evaluating an individual.
Other tests that may be done in conjunction with RSV testing include:
- Influenza tests
- Group A strep test, to detect the streptococcal bacteria that causes strep throat
- When is it ordered?
RSV tests are ordered almost exclusively during "cold and flu season" – late fall to early spring. They are ordered when someone, usually an infant or elderly person, has a serious lower respiratory infection and signs and symptoms, such as:
- Severe coughing
- Rapid breathing (primarily in infants)
- Runny, stuffy nose
- Sore throat
Testing must be done within the first few days of infection and the appearance of signs and symptoms because detectable amounts of virus are usually shed during the early phase of infection.
When RSV has already been identified in the community, a healthcare practitioner may order a rapid RSV test to confirm the suspected diagnosis in a symptomatic person.
- What does the test result mean?
If an RSV test is positive, then it is likely that the person has a respiratory syncytial virus infection. A positive test can also confirm the presence of RSV in the community. A positive RSV test cannot, however, tell a healthcare practitioner how severe a person's symptoms are likely to be or how long ago the patient was infected. Symptoms usually appear 4-6 days after infection.
Negative RSV tests may mean that the person tested has something other than RSV or that there is not sufficient virus in the sample to be detected. This may be due to either a poor specimen collection or because the person is not shedding detectable levels of virus into his or her 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 resolve 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 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 are not routinely used to diagnose RSV infections but may be used by public health officials to track RSV infections.
- 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 bacteria – so antibiotic therapy is not indicated or helpful.
- What is the treatment for RSV?
There is no specific treatment for RSV. Care for a person with RSV is primarily supportive, to minimize pain and fever and ease breathing.
There is a short-term drug therapy that is given to some high-risk people. It does not prevent or cure RSV infection, but it lowers the risk of RSV infecting the lower respiratory tract, reducing the need for hospitalization. This immunotherapy, called palivizumab, may be given to newborns in the intensive care nursery to protect them during RSV season. Premature infants can be especially vulnerable to RSV.