Why does my 3 week old baby have herpes oral sores?

First Virus Exposure: Babies have no immunity to herpes. Most adults have had exposure and may shed active virus even though they have no symptoms. Babies touch things and put fingers in their mouths and this is very common source of their first infection. See your pediatrician as 3 week olds can have severe infections that may need drug therapy to prevent complications & confirm the diagnosis.

M.D. visit: At this age, there may have been exposure during delivery. It is important to have him examined by your pediatrician. Infections may spread quickly, so this is an urgent visit.