<p>Using the WHO case definition for diphtheria, we reviewed surveillance data and conducted active case search in health facilities and communities across affected states. Nasopharyngeal and oropharyngeal swabs were collected from suspected cases for laboratory confirmation using culture, PCR and Elek test. Antibiotics sensitivity test (AST) was done on culture isolates. Descriptive analysis was conducted to describe the outbreak in terms of person, place, and time. Final case classification was based on WHO diphtheria surveillance guidelines.</p>