International Classification of Diseases

Lore & Background

The ICD's direct origin is the Bertillon Classification of Causes of Death (1893), derived from earlier work by William Farr and Marc d'Espine. French physician Jacques Bertillon introduced this classification at a congress of the International Statistical Institute in Vienna in 1891, and it was adopted at the Institute's Chicago meeting in 1893. This system, based on distinguishing general diseases from those localized to a particular organ, was adopted by several countries and expanded from 44 to 161 titles. In 1898, the American Public Health Association recommended its adoption by Canada, Mexico, and the United States, and proposed revisions every ten years. The first international revision conference took place in 1900, with subsequent revisions occurring decennially.

In 1948, the WHO assumed responsibility for the ICD, and the sixth revision (ICD-6, published 1949) was the first shaped for morbidity reporting, adding a section on mental disorders. The seventh revision (1955) was limited to essential changes and error corrections. The eighth revision (1965) was more radical but retained the basic structure and etiological classification philosophy. The ninth revision (1975) responded to growing interest by modifying the classification and introducing special coding provisions. The ICD-11, adopted in 2019 and effective in 2022, represents a fundamental architectural redesign for the digital age, with an ontological foundation, postcoordination of clinical concepts, and an annually updated API-accessible coding tool.

The ICD is part of a family of classifications that includes the International Classification of Functioning, Disability and Health (ICF) and the International Classification of Health Interventions (ICHI). Some countries, including Australia, Canada, and the United States, have developed their own adaptations of ICD with additional procedure codes.

Reader's Guide

The International Classification of Diseases is the most widely used statistical classification system for diseases worldwide. Its consistent application underpins international comparability in the collection, processing, and analysis of health statistics, forming a foundation for evidence-based health policy. The ICD is used for morbidity and mortality recording, reimbursement systems, resource allocation, and automated decision support in clinical and public health settings. The transition to ICD-11 marks a shift from paper-based editions to a digital-first architecture, enabling advanced interoperability with modern health information systems. As of July 2025, 132 WHO member states were at various stages of ICD-11 implementation, reflecting ongoing global adoption. The ICD's historical development—from Bertillon's 1893 classification to the current revision—illustrates its evolution in response to medical advances and the need for standardized health data. Its role in the WHO Family of International Classifications ensures complementarity with classifications of functioning and health interventions. While the Diagnostic and Statistical Manual of Mental Disorders (DSM) is preferred for mental disorders in some countries, the ICD remains the global standard for disease classification.

Did You Know?

• The ICD was originally called the Bertillon Classification of Causes of Death when introduced in 1893.
• The ICD-11 was adopted by the World Health Assembly on 28 May 2019 and came into effect on 1 January 2022.