Respiratory Syncytial Virus, commonly known as RSV, is a widespread respiratory virus that infects the lungs and breathing passages. It is so common that most children will have been infected with the virus by the age of two. While it can affect people of all ages, RSV is a frequent cause of respiratory illness in infants and young children.
The Typical RSV Timeline
Symptoms of an RSV infection typically appear four to six days after exposure to the virus. Initially, the illness may present with mild, cold-like symptoms such as a runny or stuffy nose, sneezing, and a mild cough. Some individuals might also develop a low-grade fever.
As the virus progresses, these initial symptoms can evolve and intensify over the first few days. The cough may become more pronounced, and a sore throat can develop. RSV symptoms often worsen gradually, leading to a peak intensity before improvement begins.
Identifying the Peak and “Worst Day”
For many individuals, particularly infants and young children, the “worst day” of RSV symptoms typically occurs around days three to five after the initial onset of symptoms. This period marks the peak severity of the illness before symptoms generally begin to subside. During this peak, common cold-like symptoms can escalate significantly.
Symptoms that become most severe during this time often include an increased cough, which can be dry or wet-sounding. Wheezing, a high-pitched whistling sound during breathing, may also become noticeable. Rapid or difficult breathing, where the chest muscles and skin pull inward with each breath, can also be a sign of distress. Infants may also show irritability, decreased activity, and poor feeding due to respiratory difficulties.
When to Seek Medical Attention
While many RSV cases resolve on their own, it is important to recognize warning signs that indicate a child’s condition is worsening and requires immediate medical evaluation. Difficulty breathing is a primary concern, which can manifest as rapid, shallow breaths, flaring nostrils, or the skin between the ribs or under the neck pulling in with each breath. A bluish discoloration around the mouth, lips, or fingernails, known as cyanosis, signifies a lack of oxygen and warrants immediate attention.
Other concerning indicators include a significant decrease in wet diapers in infants, suggesting dehydration, or extreme lethargy and unresponsiveness. For infants under three months, any fever above 100.4 degrees Fahrenheit (38 degrees Celsius) should prompt a call to a healthcare provider. If symptoms worsen or do not improve after seven days, or if a child of any age experiences a fever repeatedly rising above 104 degrees Fahrenheit, medical consultation is also advised.