Cases of respiratory syncytial virus (RSV) and influenza are rising in Brazil, prompting health officials to monitor the situation closely. While both viruses present similar symptoms, distinctions exist that aid in diagnosis, according to Marco Aurélio Sáfadi, president of the Department of Scientific Infectology at the Brazilian Society of Pediatrics.
RSV frequently affects infants in their first months of life, with studies indicating that over 95% of children are exposed to the virus by one or two years of age. The virus often manifests as bronchiolitis, beginning with fever and cough, but progressing to fatigue and respiratory distress. While not exclusive to RSV, this progression is a typical indicator of the infection.
Influenza, conversely, has generated outbreaks among older children, adolescents, and young adults. Symptoms typically include a sudden onset of fever, body aches, sore throat, cough, and runny nose. In these age groups, RSV rarely causes noticeable symptoms, making age a key factor in differentiating between the two viruses.
Globally, RSV is a leading cause of acute lower respiratory infections in children and contributes significantly to severe respiratory illness in older adults. The World Health Organization (WHO) reports that RSV causes more than 3.6 million hospitalizations annually and approximately 100,000 deaths in children under five years old, with 97% of these fatalities occurring in low- and middle-income countries where access to supportive medical care is limited.
Recent advancements include the authorization of two products for infant immunization against RSV: a long-acting monoclonal antibody administered shortly after birth and a vaccine for pregnant women in the later stages of gestation. Three vaccines have been approved to prevent severe RSV disease in adults and older individuals with underlying conditions such as lung and heart disease.
The Centers for Disease Control and Prevention (CDC) notes that RSV typically causes mild, cold-like symptoms, but remains the primary cause of infant hospitalization in the United States. Vaccines to protect adults aged 50 and older against RSV are similarly available as of July 7, 2025.
RSV is an RNA virus belonging to the Pneumoviridae family, with two genotypes, A, and B. It specifically infects human cells along the respiratory tract, from the nose to the lungs, and can cause a range of respiratory symptoms, from mild upper respiratory infections to potentially fatal lower respiratory infections.
