You are right to be concerned. Newborn babies, especially those who are premature, are at greater risk of developing complications from viral infection.

There are many respiratory viruses that can cause colds in children and adults. If there is no underlying condition, a cold can last a few days to a week, with sore throat, fever, running nose and cough. Common complications include ear infection, sinus infection, tonsillitis, etc. If a person has underlying asthma, the cough can be more severe and last much longer; asthma medicine, especially inhalers, can reduce and shorten these symptoms.

Very young infants, especially those who are born prematurely, can develop more serious illness than older children. These babies have smaller bronchial tubes that can become swollen and clogged up with mucus. They also have difficulty breathing through their nose. As a result, nursing and bottle-feeding can be difficult because they cannot breathe through their nose when feeding. Some can vomit up part or most of their feeds when they cough; this can lead to dehydration very quickly.

These premature babies are very prone to develop respiratory distress. When they breathe, they can suck in under their rib cage. They can have difficulty absorbing oxygen through their lungs, and getting rid of carbon dioxide from their body. These babies can get seriously ill with virus infections. Doctors often call it bronchiolitis. It is not uncommon for these babies to require intensive care for days before they improve.

It looks like your older son did have bronchiolitis when he was two months old. It is good to know that he is now a healthy little boy. However, he can pass on the cold virus to his little sister. You can reduce the chance by having him wash his hands with soap and water before he touches his sister. If he can wear a small face mask when he gets close to her, this can reduce the chance of him spreading the virus by sneezing and coughing. You can find these masks at pharmacies. You and your husband can do the same.

There is no guarantee that these precautions will work perfectly. I won’t recommend excessive use of chemical sprays or wipes to sanitize everything and everywhere at your home. Your children need to be exposed to normal healthy germs in the environment to boost their normal immunity.

If she does get sick, watch her breathing and feeding carefully. If you find that she is breathing too fast, or if she has difficulty breathing, get hold of your doctor or go to emergency room. Young premature babies can deteriorate quickly. One important sign to watch for is poor feeding or vomiting after feeding. When that happens, she will have less urine in her diapers also.

In the meantime, make sure everyone in your family gets the flu shot to prevent influenza infection. If you and your husband didn’t have whooping cough vaccine recently, get a booster shot; this can protect your baby from pertussis, which is a serious bacterial infection.