"First Contact" Effect on Cholera Mortality in Haiti

Official statistics are often quoted in terms of total aggregated case counts and total aggregate deaths at the national or departmental level.  For example, as of today, there have been 16,700 cases and 1,034 fatalities with a case fatality rate-apparent of 6.2%.  From an operational perspective, this yields little information to guide rapid medical support deployment. 

Once we have been sensitized to report of sudden inundation of a clinic with suspect cholera cases, subsequent examination of epidemiological data offers insight into how a clinic is progressing.  Acquisition of epidemiological data usually happens several days after "first contact" with cholera due to the operational distraction of managing the sudden influx of patients.  Progess is determined by effective management of the balance between patient demand, medical response resources (i.e. personnel and materiel), and positive adaptation over time of processes, procedures, and experience to streamline efficient diagnosis and care of the patients. 

Clinics experiencing "first contact" with cholera are usually observed to have dramatically high daily mortality as they adapt to the sudden challenge, as shown in the below examples of Cap Haitien city, Plaisance, and Limbe (green boxes).  This is particularly true for clinics unprepared or staffed with personnel with little experience recognizing and treating cholera, as is was the case in the Cap Haitien region.

It is notable that Cap Haitien experienced later surge than Plaisance and Limbe and was better resourced when they experienced first contact, which may explain the lower daily mortality.  This is a strong argument for near-real time, network-centric situation awareness as facilitated by the HEAS.  At the Plaisance and Limbe facilities, daily mortality declined despite an increase in case counts.  At the Cap Haitien facility, however, we are concerned about the persistenly high daily clinic mortality.  MSF is mobilizing to assist them now.

The argument for prior experience and forewarning is further supported by examination of the data from MSF cholera treatment centers in Port au Prince, where daily clinic mortality has not breached 10%.  MSF as an organization has experience treating cholera in other parts of the world and also was sensitized by a combination of their experience in Artibonite and sensitization to warnings issued about the entry of cholera into Port au Prince.

 

 

 

 

Comments

[Stephen Nuchia]

There are alternative explanations, considering this data purely as an exercise in statistical analysis. The proposed explanation, that the medical staff is not initially prepared to handle cases and thus salvages fewer patients than they otherwise might is certainly supported by anecdotal reports.

An alternative explanation, though, is also supported by anecdotal reports. The affected population is not yet sensitized to the diagnosis and treatment decision tree and this delays presentation of serious cases too long, leading to a very high initial fatality rate among those cases that present at the facilities.

Both explanations are consistent with the attenuation of the first contact spike in Port au Prince. Probably both play a role. One in the numerator, the other in both the numerator and the denominator.

[James M. Wilson V, MD]

Stephen,

Certainly community sensitization is a factor, where spread by word of mouth to 1) not delay in seeking treatment and 2) "here's where you need to go" are key.

Variability seen in some of the facilities like multi-modal spikes of cases we believe reflects spread from one village or neighborhood to another within a large patient catchment area.

Jim