2.3 Initial on-site investigation

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    Once an alert has been verified, the on-site investigation should be undertaken within 24 hours.

    2.3.1 Preparation of the investigation

    Ideally the investigation team is composed of a doctor or nurse and a logistician and/or a water/sanitation specialist. Each team member should have determined tasks in the investigation. If creating such a team is not immediately possible, the investigation should not be delayed and a single person can conduct the investigation if s/he is experienced.


    Prepare medical supplies for diagnosis (Appendix 1) and treatment of some cholera cases (Appendix 2).


    Contact local Ministry of Health and governmental representatives. Explain the reason for the investigation and request authorization and assistance (access to all sites, persons and data necessary to complete the investigation).


    Consider a visit to surrounding villages or health posts to help determine the extent of the problem.

    2.3.2 Investigation inside the health facility

    • Clinical examination (Section 2.4.1) and stool sample collection (Section 2.4.2) for diagnosis confirmation.
    • Capacity of the health facility to respond immediately to the needs, and quality of care:
      • Number of current beds and potential bed capacity;
      • Available human resources (medical and non-medical) and prior experience with cholera case management;
      • Use of standard case definition and treatment protocols;
      • Hygiene practices (isolation, hand-washing, etc.);
      • Stock of drugs and medical supplies, logistic materials, and supply chain;
      • Water supply (quantity and quality, Appendix 17);
      • Number of latrines and showers, solid waste and waste water management systems.
    • Current data on cholera cases and deaths (and, if available, historical data; however these data may be available at the central level only).
    • Accessibility of the treatment facility (location, transportation, security, fee for service, etc.).

    2.3.3 Investigation outside the health facility

    • Local demographic data (these data may be available at the central level only).
    • Factors contributing to an epidemic:
      • High population density (camps and slums);
      • Gathering places (markets, transportation hubs, schools, and other congregate settings);
      • Sources of drinking water potentially contaminated (unprotected wells, surface water, street vendors, etc.);
      • Poor water quality (excessive turbidity and absence of free residual chlorine, see Section 3.3.3 and Appendix 17);
      • Poor sanitation (open defecation, poorly maintained public latrines, broken sewer pipes, etc.);
      • Current meteorological conditions (rain, flooding, drought, etc.).
    • Presence, capacity and role of other actors (organizations, associations, etc.).


    For each place visited, draw a map to locate settlements, health facilities, water sources (indicate whether they are treated/protected or not), gathering places, and major transportation routes.

    2.3.4 Immediate actions

    • If patients are deemed to be at risk due to gaps in:
      • Supplies:

    Essential medical material should be provided: as a minimum Ringer lactate (RL), catheters, infusion sets and other infusion supplies (compresses, tourniquet, antiseptic, tape, etc.) and oral rehydration salts (ORS), as well as doxycycline for prescription in appropriate cases.

    • Case management:

    The doctor or nurse of the investigation team should provide direct patient care and rapid bedside training.

    • If suspected cases are not isolated, put them together in a separate area to prevent exposure to others.
    • If there is no cholera-specific register, set one up (Appendix 3).


    Note: as cholera outbreaks move with populations it is important to remain flexible. It will likely be necessary in most open settings to continue similar investigations in new neighbourhoods or villages throughout the epidemic.