CDC warns on uptick in RSV cases after low activity during COVID-19: What to know about respiratory illness

The Centers for Disease Control and Prevention (CDC) national surveillance system has noted an uptick in the number of respiratory syncytial virus (RSV) cases detected in the U.S. over the last several weeks, noting that the illness can be associated with severe disease in young children and older adults. 

RSV is a common respiratory virus that usually causes mild, cold-like symptoms, but resolves within a week or two. Nearly all children are expected to have had an RSV infection by their second birthday. However, due to low numbers over the last year, the agency is warning that older infants and toddlers may be at an increased risk of severe illnesses since they did not have the usual amount of exposure. 

The agency sent out a health advisory last week noting an uptick particularly in the southern regions and advised health care workers to institute broader testing for RSV presenting with acute respiratory illness but test negative for SARS-CoV-2. 

RSV infections in the U.S. typically occur during the fall and winter cold and flu seasons, but in April 2020 there was a rapid decrease in activity "likely due to the adoption of public health measures to reduce the spread of COVID-19." 

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It remained low from May to March 2021, but since then there has been an observed increase in the number of cases reported to the National Respiratory and Enteric Virus Surveillance System (NREVSS). Health officials are warning that due to the unusual nature of the spike, there is no roadmap to predict when a peak will occur or the duration for which transmission will remain high. 

"Due to reduced circulation of RSV during the winter months of 2020-2021, older infants and toddlers might now be at increased risk of severe RSV-associated illness since they have likely not had typical levels of exposure to RSV during the past 15 months," the CDC warned. "In infants younger than six months, RSV infection may result in symptoms of irritability, poor feeding, lethargy, and/or apnea with or without fever. In older infants and young children, rhinorrhea and decreased appetite may appear one to three days before cough, often followed by sneezing, fever and sometimes wheezing." 

In adults, symptoms are typically consistent with upper respiratory tract infections including rhinorrhea, pharyngitis, cough, headache, fatigue and fever. For severe cases, however, it can also cause more severe infections such as bronchiolitis, an inflammation of the small airways in the lung, and pneumonia, an infection of the lungs. It is also the most common cause of bronchiolitis and pneumonia in children younger than 1, according to the CDC. 

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With most infections, the virus will clear on its own, so there is no specific treatment although work is underway on potential vaccines or antivirals. Managing fever or pain with over-the-counter medications and drinking fluids can help alleviate symptoms.