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. .

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. .

"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 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." 

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