Sometimes newborns catch a viral infection. Viruses cause colds, flu, and some diseases such as herpes and chickenpox. A virus may travel from the placenta into a baby's bloodstream before birth. Or the baby may be exposed to a virus in the birth canal during delivery. Occasionally, a newborn catches a viral infection after birth by being exposed to someone with a cold.
Newborns can get sick very fast.
Babies respond very quickly to antibiotics. They do extremely well if they start getting antibiotics when an infection has just begun. The early signs of infection are subtle and not specific. For example, at first it may not be known whether a baby's fast breathing is caused by an infection or by fluid in the lungs. If treatment is not given until it is certain the baby has an infection, the baby may become quite sick and require intensive care.