Cholera Outbreak Toolbox

Cholera Outbreak Toolbox

Updated | September 2024

Welcome to the Cholera Outbreak toolbox

Key reference documents

Case definitions

Principles:
  • Different case definitions apply depending on the prevailing cholera situation in a surveillance unit.
  • A surveillance unit corresponds to the lowest administrative level at which decisions are made to
    trigger cholera prevention and control measures and surveillance findings are used to inform local
    public health interventions. The corresponding administrative level is country specific and
    typically corresponds to administrative levels two or three. 
  • In surveillance units where there is no probable or confirmed cholera outbreak, using a more 
    specific definition (one that specifies the patient’s age and dehydration level) helps to avoid
    frequent, false suspected cholera cases/outbreaks from being detected, which could overwhelm
    the capacity of the surveillance system and decrease its effectiveness at early detection.

WHO suggested outbreak case definition

Suspected cholera case:
In the absence of a probable or confirmed cholera outbreak
A person aged two years or older: with acute watery diarrhoea and severe dehydration;
or
who died from acute watery diarrhoea with no other known cause of death.

In the presence of a probable or confirmed cholera outbreak
A person with acute watery diarrhoea or who died from acute watery diarrhoea.
Confirmed cholera case:
  • Any person infected with Vibrio cholerae O1 or O139, as confirmed by culture (including seroagglutination) 
    or PCR.
  • The bacterial strain should also be demonstrated as toxigenic (by PCR) if there is no confirmed cholera outbreak in other surveillance units, and no established epidemiological link to a confirmed cholera
    case or source of exposure in another country.
  • Importantly, commercially available Rapid Diagnostic Tests (RDTs) cannot be used to confirm individual cholera cases.

WHO outbreak definition

Suspected cholera outbreak is defined by the detection of at least one of the following:

Two or more suspected cholera cases or one suspected cholera case with a positive RDT result reported in a surveillance unit within seven days.  

The detection of a suspected cholera outbreak should trigger immediate public health measures for acute diarrhoeal diseases without waiting for laboratory confirmation of cholera.

Probable cholera outbreak

The number of suspected cholera cases with a positive RDT result within 14 days meets or surpasses a defined threshold while taking into account the number of suspected cases tested:
 
 Number of suspected cholera cases tested by RDTNumber of suspected cholera cases with RDT+ result 
 3 to 7
8 to 10
11 to 14
15 to 17
18 to 21		≥ 3
≥ 4
≥ 5
≥ 6
≥ 7

A probable cholera outbreak corresponds to a situation where there is high confidence that a cholera outbreak is occurring. Laboratory confirmation of cholera often takes time, and the disease can spread very rapidly, so detecting a probable outbreak through RDTs allows for a rapid, extensive, and comprehensive cholera outbreak response to be initiated without waiting for laboratory confirmation.

Confirmed cholera outbreak

At least one locally acquired confirmed cholera case is detected in a surveillance unit.

 For more information on cholera case and outbreak definitions:

Acute watery diarrhoea:

An illness in which: 

  • Acute is defined as lasting less than seven days;
  • Watery is defined as non-bloody liquid stools that may contain mucous;
  • Diarrhoea is defined as three or more loose stools within a 24-hour period.

 

Data collection tools

From Public Health Surveillance for Cholera – Guidance Document 2024 (Global Task Force on Cholera Control; April 2024): 

Laboratory confirmation