Updated Case Counts And Implications For Sustained Transmission

From our perspective, we agree with PAHO's recent statement today about the epidemic and while we all would like to be hopeful, we are reminded of the recent 2008-2009 epidemic of cholera in Zimbabwe.  Responders there were lulled into a false sense of security as the epidemic waned, only to be badly disappointed as the epidemic continued onward to produce 98,424 suspected cases and 4,276 deaths (Case Fatality Rate of 4.3%) from August 2008 to June 2009 that were officially reported. Fifty-five out of 62 districts in all 10 provinces had been affected, according to the World Health Organization.

Currently we are seeing 4,147 cases officially reported, with 292 deaths.  We assume PAHO is reporting these as separate groups of people, where the total number of cases reported is actually 4,147+292= 4,439.  If we generally assume that only 25% of cases display clinically apparent illness, we conservatively assume then there has been at least 17,756 infected people to-date.  This is a truly alarming number of people, especially when considering 1) this is likely the result of under-reporting and 2) a large percentage of these infected individuals could be shedding pathogen into the environment for weeks post-infection.

There are a number of factors in play to explain the apparent high CFR:
 
1.  CFRs are often inflated at the front-end of outbreaks and epidemics in general, especially when dealing with an area of limited infectious disease warning capability, because the social bias in reporting up to a national level is driven by fatalities or the most severe clinical outcomes.

2.  Once the clinical entity (i.e. cholera) is recognized to be the etiological agent, extrapolations for the true infectious disease load in community may then be calculated for a truer estimate (such as we've proposed above).

3.  Once social sensitization has been achieved through a warning process such as we have achieved, reminders for clinical diagnosis are also distributed which actually alters the probability of clinical diagnosis for milder cases.  This means your reported case count may migrate a bit over time.

Bottom line, our team remains on maximum alert and are concerned about the potential for ecological establishment and introduction to other nations in the Caribbean.