has the pediatrician advised nebulizer? what medicine are you giving in the nebulizer? if there any fever along with cough and cold? this is mostly because of season change and newborns are prone to upper respiratory born infections a lot.

Viral fever duration for most viral infections is 3-5 days , in few cases it may take 14 days

Please consult with your current neurologist as he/she has the best knowledge about your case. I am not aware what treatment are you taking so don’t want to advise you anything with the incomplete information.