A few weeks ago, Angelique Lucero's 2-year-old daughter Sophie was diagnosed with the respiratory illness RSV, short for Respiratory Syncytial Virus.
Similar to the flu, but with no vaccine and slightly different symptoms, it can be spread quickly at daycare centers.
Sophie recovered quickly, but when her little brother Zaiden, just 6 weeks old, began coughing and then throwing up on New Year's Eve, Lucero knew it was serious.
Zaiden is now at Childrens Hospital Colorado in Aurora.
“I never heard of RSV, I just heard of the flu, but I didn’t think it was this serious in kids," said Lucero. "I did not."