Respiratory syncytial virus, or RSV, is a single-stranded virus that originates from RNA. Illness from RSV is considered an infectious disease, usually leading to an infection of the upper respiratory tract but possibly causing lower respiratory tract infections as well. Each year, RSV infections lead to about 58,000 hospitalizations and up to 500 deaths in children under 5, as well as 177,000 hospitalizations and 14,000 deaths in adults aged 65 years or older. Kannika Paison / Getty Images RSV usually causes mild, cold-like symptoms, which don’t appear all at once. A person with RSV will show symptoms within four to six days after infection. Those symptoms can include: RSV can affect anyone; most individuals will improve in a week or two. However, two primary populations may experience severe infections from RSV: infants or young children and older adults. Infants and Young Children Premature and very young infants will likely experience severe illness resulting from ...