[1][2][3] Nwosu was born in Obiuno Udede, Otolo, Nnewi, Anambra State, Nigeria.
He completed his early education at local primary and secondary schools before attending the University of Nigeria, Nsukka (UNN), where he graduated in 1971 with a B.Sc.
[4][2] Nwosu worked as a lecturer at UNN from 1981 to 1986 and concurrently served as the dean of the Faculty of Science at Anambra State University of Technology, Enugu, from 1981 to 1984.
He was a member of the Presidential Advisory Committee on Health and later served as special adviser to President Olusegun Obasanjo on political matters.
In February 2001, he was appointed minister of health, where he led efforts to combat infectious diseases and implement healthcare reforms, including the establishment of the National Health Insurance Scheme (NHIS).