Cholera surveillance during the Haiti epidemic

This week's issue of the New England Journal of Medicine reviews data from the National Cholera Surveillance System.

In October 2010, nearly 10 months after a devastating earthquake, Haiti was stricken by epidemic cholera.

Within days after detection, the Ministry of Public Health and Population established a National Cholera Surveillance System (NCSS).

The NCSS used a modified World Health Organization case definition for cholera that included acute watery diarrhea, with or without vomiting, in persons of all ages residing in an area in which at least one case of Vibrio cholerae O1 infection had been confirmed by culture.

Dr Ezra Barzilay and colleagues reviewed the NCSS data on cholera surveillance during the Haiti epidemic.

Within 29 days after the first report, cases of V. cholerae O1 (serotype Ogawa, biotype El Tor) were confirmed in all 10 administrative departments in Haiti.

The team report that through October 2012, the public health ministry reported 604,634 cases of infection, 329,697 hospitalizations, and 7436 deaths from cholera and isolated V. cholerae O1 from 62% of stool specimens tested.

The team observed that the cumulative attack rate was 5% at the end of the first year, and 6% at the end of the second year.
 
The cumulative case fatality rate consistently trended downward, reaching just over 1% at the close of year 2, with departmental cumulative rates ranging from under 1% to almost 5%.

Within 3 months after the start of the epidemic, the rolling 14-day case fatality rate was 1%, and remained at or below this level with few, brief exceptions.

The team noted that the cholera epidemic in Haiti accounted for 57% of all cholera cases, and 53% of all cholera deaths reported to the World Health Organization in 2010, and 58% of all cholera cases, and 37% of all cholera deaths in 2011.

Dr Barzilay and team comment, "A review of NCSS data shows that during the first 2 years of the cholera epidemic in Haiti, the cumulative attack rate was 6%, with cases reported in all 10 departments."

"Within 3 months after the first case was reported, there was a downward trend in mortality, with a 14-day case fatality rate of 1% or less in most areas."