Respiratory Syncytial Virus (RSV) is a common and contagious pathogen that causes respiratory tract infections in people of all ages. Most children contract RSV by age two, and reinfection is frequent throughout adulthood. The illness typically presents with cold-like symptoms but can progress to serious lower respiratory tract diseases, such as bronchiolitis or pneumonia, especially in infants and older adults. The significant nasal congestion and discharge associated with RSV often raise the question of whether the virus transforms into a true sinus infection.
How RSV Affects the Upper Respiratory System
RSV primarily targets the epithelial cells lining the upper airways, causing an inflammatory response known as rhinitis. This inflammation results directly from the virus infecting the nasal passages, leading to typical cold symptoms. A hallmark of upper respiratory RSV infection is often profuse mucus production, resulting in a persistent runny nose (rhinorrhea).
Nasal congestion and discharge are part of the body’s defense mechanism against the virus. Inflammation causes the mucous membranes to swell, narrowing the nasal passages and creating stuffiness. This severe congestion, often accompanied by a cough and low-grade fever, is a manifestation of the viral illness itself, not a complication. Symptoms of viral rhinitis, including a runny nose that may turn yellow or green, typically last for one to two weeks.
Understanding Secondary Bacterial Sinusitis
A true sinus infection, medically termed Acute Bacterial Rhinosinusitis (ABRS), is distinct from the viral inflammation caused by RSV, though it can occur as a secondary complication. Sinuses are air-filled cavities that normally drain mucus through small openings into the nasal cavity. When RSV causes severe swelling and inflammation of the nasal lining, these narrow drainage pathways can become blocked.
This blockage causes mucus stasis within the sinuses, creating an environment hospitable for bacterial overgrowth. The subsequent infection is bacterial, resulting from the compromised clearance mechanisms of the sinuses, even though the initial infection was viral (RSV). RSV infection is known to cause the epithelial damage and inflammation that enhances susceptibility to this secondary bacterial invasion. Only a small percentage of viral upper respiratory infections, estimated at 0.5% to 2.0%, progress to a bacterial sinus infection.
Recognizing Signs of a Secondary Infection
Distinguishing between persistent viral symptoms and a true secondary bacterial sinus infection is important because the latter may require antibiotics. Most cases of viral rhinitis, including those caused by RSV, gradually improve within seven to ten days. A key indicator of a secondary bacterial infection is a lack of symptom improvement after this period, or an initial improvement followed by a distinct worsening.
This worsening, sometimes called “double sickening,” often involves the recurrence of a high fever, more intense localized facial pain or pressure, or a return to a sicker appearance. While discolored mucus alone does not diagnose a bacterial infection, persistent, thick, yellow or green discharge accompanied by new or worsening symptoms can signal a secondary infection. Older children may report headaches or pain in the forehead or under the eyes, which are common complaints with bacterial sinusitis. If symptoms are severe, such as a high fever greater than 101.5 degrees Fahrenheit or facial pain lasting more than three days, medical evaluation is necessary.