Sunday, October 24, 2010



Please note this is a map not of case counts, but of sites in Haiti where we now assume or have confirmed the presence of cholera. From an operational biosurveillance perspective, we are now singularly focused on local capacity to provide appropriate medical care to avoid unnecessary loss of life in the context of social stability. The Infectious Disease Impact Scale (IDIS) is used for this purpose:

IDIS Category 0. Unreported infectious disease event. Daily, routine infectious diseases are handled at this level, and provision of warning about these diseases is not deemed ‘relevant’. It is likely there are multiple unreported cholera cases now inside Port-au-Prince, for instance, and in Artibonite and perhaps elsewhere.

IDIS Category 1. Reported infectious disease event. The typical Category 1 infectious disease event reported by a community reflects a sensitivity to public health or medical significance. No other significant features indicative of immediate public health or medical infrastructure impact, public anxiety, or civil unrest triggered by the event are noted.

IDIS Category 2. Infectious disease event associated with routine organized response. Category 2 events often reflect locally well-known diseases that nevertheless generate a demand for organization-level time-sensitive action. This action is local routine.

IDIS Category 3. Infectious disease event associated with non-routine organized response. Category 3 events are essentially the beginnings of a community crisis.

IDIS Category 4. Infectious disease event associated with social disruption. Category 4 events highlight when organized response has occurred, yet significant social disruption has been documented.

IDIS Category 5. Infectious disease event associated with disaster indicators.

IDIS Category 6. Infectious disease event associated with apocalyptic indicators. This is an operationally rare finding, associated historically with Ebola and Nipah virus outbreaks. We do not consider this category to represent a likely scenario in Haiti.

Current situation map of the Haiti cholera epidemic based on IDIS Category. As noted, there remains much uncertainty as to the status of several specific local communities' capacities to handle patient demand.

IDIS Cat 3 conditions in Port-au-Prince indicate awareness of an influx of confirmed cholera cases; organized response is currently being cued by awareness of preceding events in Artibonite, whereas cholera was unexpected in Artibonite, which arguably hindered rapid alerting and response.

Red arrows denote apparent vectors of cholera case influx from the original epidemic zone in Artibonite. Northernmost lead edge is within proximity to Cap Hatien, southernmost is Port-au-Prince. We have no report of cases in Leogane, which was the epicentre of quake damage and the most vulnerable to an epidemic of cholera from the viewpoint of access to basic medical care.

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