Abstract
Under the framework of Defeating meningitis by 2030: a global road map, the World Health Organization has developed and updated standard case definitions to strengthen disease surveillance, support timely outbreak detection and response, and ensure consistent data collection and reporting across health care settings and systems. This document provides ministries of health, public health agencies, and national and international organizations with a practical framework for applying standard case definitions of acute bacterial meningitis and invasive meningococcal disease in different epidemiological contexts. Grounded in an evidence-based approach, it offers guidance on identifying and classifying suspected, probable, and confirmed cases for routine surveillance, outbreak investigation and response, and humanitarian emergencies. The web annex sets out the full body of evidence that informed the development and updating of the case definitions.