In an undated family photo, Andre Salahshour, who was hospitalized at six weeks old due to respiratory syncytial virus, or RSV. Though nearly every child contracts RSV, it typically presents as a bad cold. But for some, it causes breathing problems and dangerous lung infections — and many parents have never heard of it until their child becomes ill. (Alexandria Salahshour via The New York Times) -- NO SALES; FOR EDITORIAL USE ONLY WITH STORY SLUGGED RESPIRATORY VIRUS BY CARON FOR JAN. 11, 2018. ALL OTHER USE PROHIBITED. --.