It looks like: A bad cold with a high fever (and occasionally diarrhea or vomiting) that comes on quite suddenly. Babies with flu are also fussy because they feel so awful, says pediatrician Luke Beno, M.D., with Kaiser Permanente in Atlanta.
What's happening: You should take this respiratory infection seriously. Among children, babies younger than 6 months old have the highest risk of being hospitalized and also have the highest rates of flu mortality. That's largely because their immune system hasn't fully developed and they're too young to have a flu shot. However, if you were vaccinated when you were pregnant, your antibodies cut your baby's flu risk by 41 percent during those first six months, according to research. After that, she'll be old enough for her own shot. Get the rest of the family and caregivers immunized, too, advises Orlando pediatrician Hernando Cardona, M.D., of Windermere Pediatrics. "The only way Baby is going to contract flu is if someone brings it home," he says.
Call the doctor: If it's flu season (November to April), and your little one spikes a fever, see your doc that same day. A rapid test of nasal secretions can confirm that she has influenza, and your M.D. may administer an antiviral, such as Tamiflu, which can speed recovery by a day or so. Tamiflu is generally not recommended for children younger than 12 months, "but when a baby is really sick, we'll give it, because the younger they are, the higher their risk for complications," Dr. Cardona says. One of the most common is pneumonia, which develops when a flu virus migrates into the lungs from the nose and throat, or when a bacterial infection has cropped up as well. Viral pneumonia is treated with comfort measures; bacterial pneumonia requires antibiotics.