Welcome to the Chemical Hazards Outbreak toolbox

Key reference documents

• Chemical Safety and Health (Geneva: World Health Organization).
• Manual for investigating suspected outbreaks of illnesses of possible chemical etiology: Guidance for investigation and control (Geneva: World Health Organization).

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Case definitions

Who suggested outbreak case definition?¹

There are no generic outbreak case definitions for chemical hazards. Case definitions may comprise various combinations of clinical, environmental, laboratory and epidemiological criteria:

• clinical presentation of agreed signs, symptoms and toxidromes.
• laboratory analyses (when available or appropriate) of biomarkers of exposure and of effect.
• chronology: the period during which identified cases can be considered part of the outbreak, e.g., period considered of exposure to the chemical
• geography: residence in a potentially exposed area or visiting the area during the suspected period
• of exposure
• demographics: inclusion of those most likely to be affected, e.g., by age group, occupation, or gender 

Cases may be classified according to the certainty of the diagnosis: 

• Suspected case: person presenting with clinical features consistent with the outbreak and considered for laboratory or other diagnostic investigation 
• Probable case: person presenting with clinical features consistent with the outbreak and resident in
• the affected area during the defined period, or a person presenting with the clinical features of concern
• and epidemiological links to an analytically confirmed case
• Confirmed case: person presenting with clinical features consistent with the outbreak, resident in the
• affected area during the defined period and with laboratory or diagnostic confirmation.

WHO surveillance case definition
There are currently no WHO surveillance case definitions for specific chemical hazards. Please refer to US Centers for Disease Control and Prevention (CDC) websites: 

_{1. Source: WHO Manual for investigating suspected outbreaks of illnesses of possible chemical etiology: Guidance for investigation and control. (Geneva: World Health Organisation; 2021).}

Data collection tools

Laboratory confirmation

Response tools and resources

Other resources