By Mike Blaivas, MD, MBA, FACEP, FAIUM, Chief Medical Officer

RSV (respiratory syncytial virus) is a term many physicians have known for years, and most have largely ignored. Until approximately 3 years ago, unless you were an Emergency Medicine Physician like me or in a pediatrics related field, RSV was essentially irrelevant. Most children were thought to have had RSV by age 2 and if they got it later it rarely caused significant illness. If physicians accidentally ordered an RSV test in an adult, they would probably be ridiculed by the hospital laboratory and if a positive result came back, it would then be dismissed.

For those on the front lines in the emergency department, RSV was a wild card illness. Most kids with it had a runny nose and mild fever, requiring nothing but Tylenol. But occasionally, we would see a child with severe bronchiolitis from the virus and they could literally die in hours if not given intensive care measures including being put on a ventilator. In fact, some still died despite this. Unfortunately, some young children seemed okay one day when seen in the ED and would be near death a day or two later.

We always knew this virus could be deadly, but we never realized that it was also a problem for older adult patients. There was some early research suggesting this was a problem, but for the rank and file it wasn’t until many older patients started to get tested for RSV unintentionally. This happened when we ordered respiratory infection panels or tests looking for a broad range of infections in sick patients who did not have any apparent bacterial infection.  Now we know the virus can be deadly to older frail patients as well as kids and infection is not just for toddlers and younger. Fortunately, there may be something to do about it as well.

There are two types or subgroups of RSV, A and B. More is known about type A than B, because it is easier for researchers to study.  RSV targets the upper respiratory tract and attaches to epithelial cells or the inner lining cells of the nose and throat. When infected by RSV, these cells get inflamed which causes damage to cells and results in congestion, cough, runny nose and sneezing. Occasionally, the virus can travel to the lower respiratory tract or trachea and lungs causing inflammation there. In infants and young children so much swelling and mucous production can occur in the trachea and lungs that the airways are actually plugged up causing trouble breathing, sometimes severe. This is what gets some of the littlest children in so much trouble.

Testing for RSV has evolved considerably in the last few years. The old gold standard was to perform a viral culture, but the results took several days to get back. Sincere there was no specific medication to treat RSV the delay didn’t impact treatment but allowed an infected child to spread the virus to others. The current gold standard is called RT-PCR or just PCR. This is the testing type all other tests are compared to. These include rapid antibody and antigen tests, which pick up the virus between 74 and 86% of the time when the virus was actually present in the sample. These results are consistent with differences in accuracy between molecular type tests like PCR and the rapid tests in other viruses like the Flu and Covid-19. Samples for these tests can range from the dreaded nasopharyngeal swab to lower nose swabs, throat swabs and even sputum (spit) tests.

Unlike a few years ago, where there were not treatments for RSV specifically, even for kids so sick we put them on ventilators; we now have some options to directly target the virus. It’s important to note that most children infected with RSV will still just have a runny nose, mild congestion, cough and maybe fever, thus requiring nothing except for Tylenol or ibuprofen.  Our best direct treatment and prevention option for young children have catchy names like Nirsevimab and Palivizumab. These are monoclonal antibody treatments that bind to specific proteins on the RSV virus itself. This is not new technology, but essentially clones one antibody, that successfully interferes with the virus, into millions of antibodies. When injected into a human, they seek out RSV viruses sticking to them and interfering with virus activity. Like most such antibody treatments, they have to be administered before the patient is really sick, or it may be too late to make a difference. Right now, the CDC recommends monoclonal antibody administration for infants under 8 months of age who are at risk for RSV due to time of year or other factors. Kids between 8 and 19 months of age with special risks can also benefit from an antibody treatment to prevent severe disease. The effects of these shots last for several months, but they don’t start working immediately.

There are several RSV vaccines available, and the number is likely to grow in the upcoming years. Currently, the CDC recommends one of two RSV immunizations for adults 60 years or older who may choose to receive it after discussion with their physician. There is one vaccine option for pregnant women during week 32 to 36 of their pregnancy, which is expected to lead to protection of the newborn.

The concept of adults being “at risk from a kid virus” is something new for medicine. However, a study in 2022 suggested that RSV caused almost 160,000 hospitalizations and from 9,500 to 13,000 deaths in patients over 65 years of age. This is a relatively new realization for the house of medicine as a whole and attention on this topic is critical. One of the reasons this has not been well known in the past is lack of good testing options and little testing in adults. The first and last RSV test I ever received was on a pediatrics rotation in medical school during which I was pretty sure my professor poked a hole in the top of my nose all the way into my brain. Luckily, much better sample collection options exist now.

From an academic side of things, it will be interesting to watch infection patterns change as more children are protected by RSV vaccines. While it might greatly reduce severe RSV infections in kids, it may make room for other viruses to slide in. We have seen similar changes from other pediatric vaccines and it’s simply a natural part of targeting specific diseases of childhood. Interestingly, there is growing scientific study evidence that preventing lower respiratory tract infection in young children may reduce hospitalizations later in childhood from other respiratory related problems and have long term benefits such as improved lung health and lower antibiotic use. We may have finally entered an era where we can combat and control RSV, saving thousands of young and old alike. The key now is the broad availability of very accurate testing options to pick up infections as early as possible.

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The AscencioDx® Covid-19 Test and The AscencioDx® Molecular Detector have not been FDA cleared or approved, but have been authorized for emergency use by FDA under an EUA for use by authorized laboratories. This product has been authorized only for the detection of nucleic acid from SARS-CoV-2, not for any other viruses or pathogens. The emergency use of this product is only authorized for the duration of the declaration that circumstances exist justifying the authorization of emergency use of in vitro diagnostics for detection and/or diagnosis of COVID-19 under Section 564(b)(1) of the Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 360bbb-3(b)(1), unless the declaration is terminated or authorization is revoked sooner.