- A review of the National Cholera Surveillance System data in Haiti during the first 2 years of the cholera epidemic showed that the cumulative attack rate was 6.1%.
- The strain of cholera involved in the epidemic has been shown to be similar to those circulating in Asia and different from those found in Latin America and the U.S.
Over its first 2 years, the cholera outbreak in Haiti sickened more than 600,000 people and killed nearly 7,500, researchers reported.
The surprise outbreak hit a population still reeling from the Jan. 12, 2010 earthquake and with little or no exposure or immunity to cholera, according to Ezra Barzilay, MD, of the CDC, and colleagues.
As a result, the Haiti outbreak was the largest national outbreak in recent memory, accounting for 57% of all cholera cases and 45% of cholera deaths reported to the World Health Organization in 2010 and 2011, Barzilay and colleagues reported online in the New England Journal of Medicine.
Haiti had been free of cholera for nearly a century, but it appeared in two central provinces in October, 2010 and had spread throughout the country within a month.
The arrival of Vibrio cholera was “inadvertent,” Barzilay and colleagues reported; the strain involved has been shown to be similar to those circulating in Asia and different from those found in Latin America and the U.S.
There has been speculation that it was introduced to Haiti by troops from southeast Asia who were part of the earthquake relief effort.
Using data from the swiftly improvised National Cholera Surveillance System, Barzilay and colleagues paint a picture of a shattered nation trying, without previous experience, to cope with an unexpected epidemic.
The first reports of illness associated with water diarrhea and dehydration came to the Haitian health ministry on Oct. 19, 2010, the researchers reported. Within 2 days, public health workers had identified cholera in the stool of several patients and notified international health authorities.
There had been no previous need for national cholera surveillance and now, Barzilay and colleagues wrote, Haiti was forced to establish such a system in the face of important challenges.
The earthquake had seriously damaged the country’s health care, water and sanitation systems, which had already been precarious. In 2008, Barzilay and colleagues note, only 63% of Haiti’s 9.8 million people had access to an “improved drinking water source,” just 12% got piped and treated water, and only 17% had adequate sanitation.
The international goal in a cholera outbreak is a case fatality rate of no more than 1%. That “was made more challenging because of these conditions,” Barzilay and colleagues reported.
Through the first 2 years, the surveillance data showed, the outbreak had five peaks, starting in October, 2010 with a rash of cases in the central provinces of Artibonite and Centre.
Starting 29 days after the first culture confirmation, a broad second peak involved cases from all 10 of the country’s departments (equivalent to states or provinces) and case counts were 4,000 a day or more.
Smaller peaks were seen in mid-summer of 2011, again about a year after the outbreak started, and in April through June 2012.
All told, the new national surveillance system recorded 604,634 cases, 329,697 hospital admissions, and 7,436 deaths through October, 2012, the researchers reported.
Flooding caused by Hurricane Sandy, according to press reports, has caused a renewed surge of cholera cases in Haiti.
The outbreak’s cumulative attack rate at the end of the first year was 5.1%, and rose to 6.1% at the end of the second year, the researchers reported. The cumulative case fatality rate fell over time, and reached 1.2% at the end of the second year.
The 14-day average case fatality rates reached 1% within the first 3 months of the outbreak, Barzilay and colleagues reported, and have stayed at or below that level most of the time since.
Testing showed that the cholera strain in Haiti was resistant to a range of antibiotics, including furazolidone, nalidixic acid, sulfisoxazole, streptomycin, and trimethoprim–sulfamethoxazolem, but was susceptible to ampicillin, amoxicillin–clavulanic acid, and tetracycline.
No strains were resistant to ciprofloxacin, but all showed decreased susceptibility, the researchers reported.
The authors did not report any external supprt for the study or financial links with industry.
Primary source: New England Journal of Medicine
Barzilay EJ, et al “Cholera surveillance during the Haiti Epidemic — the first 2 years” N Engl J Med 2013; DOI: 10.1056/NEJMoa1204927.