Thursday, January 28, 2016

Study: Haiti’s Cholera Epidemic Could Have Been Prevented

Cholera remains a critical risk for U.N. peacekeeping operations, years after Nepalese troops inadvertently the disease to Haiti in fall of 2010 and triggered one of the worst epidemics in recent years.

New research by scientists at Yale School of Public Health, in partnership with colleagues at the Yale Law School, has found that simple and inexpensive interventions—which the United Nations has yet to implement—would be effective in preventing future outbreaks of the bacterial infection.

Researchers developed a mathematical model for the arrival of peacekeepers carrying cholera and the early spread of the disease in Haiti. The model estimated the probability of an epidemic occurring under current U.N. protocols, and compared this against the probability of an epidemic if peacekeepers had been given antibiotics for cholera, screened or vaccinated. A team of independent scientific and medical experts had previously recommended that the United Nations consider these interventions to limit peacekeepers’ risk for spreading cholera. However, their implementation by the UN has been complicated by a lack of evidence to support decision-making.

The Yale team found that all three strategies could significantly reduce risk for cholera epidemics such as occurred in Haiti following a massive earthquake that devastated parts of the Caribbean nation. Antibiotic prophylaxis beginning one week before peacekeepers depart their home countries was the most promising strategy, reducing the probability of an epidemic by over 90 percent, at a cost well below $1 per peacekeeper. Screening for cholera infection was found to reduce the probability of an epidemic by over 80 percent at around $2.50 per peacekeeper.

The findings are published today (January 26) in the journal PLOS Medicine.

“More needs to be done by the United Nations to protect both peacekeeping personnel and the populations that they serve from cholera,” said senior author Virginia Pitzer, assistant professor in the Department of Epidemiology of Microbial Diseases at the School of Public Health. “This study provides quantitative support to show that effective strategies are available.”

Vaccination, meanwhile, was estimated to reduce the probability of an outbreak by around 60 percent at best. While cholera vaccines prevent severe symptoms when people are exposed to the pathogen, they do not necessarily prevent people from becoming infected and unknowingly transmitting to others. Given the limited supply of cholera vaccines, the researchers argue that vaccination might be better used in response to emergencies.

“One of the goals of modeling is to get a sense of the potential large-scale outcomes of different policies,” said Joseph Lewnard, the study’s lead author and a Ph.D. student at the School of Public Health. “Evidence that the available interventions are effective substantively changes the conversation about preventing cholera introduction during deployments.”

Haiti’s cholera epidemic killed close to 9,000 people and hospitalized hundreds of thousands more. The epidemic also spread to several neighboring countries.

Cholera is a diarrheal disease transmited through contaminated food and water. Severe cases can cause some victims to die of dehydration the same day they fall ill. However, far more people carry cholera bacteria without suffering severe symptoms, making it hard to know who is infected and capable of spreading the disease.

Other authors include Marina Antillón and Gregg Gonsalves, Ph.D. candidates at the School of Public Health; Alice Miller, associate professor (adjunct) at Yale Law School and assistant clinical professor at School of Public Health; and Albert Ko, professor at the School of Public Health.

Yale’s Global Health Justice Partnership (GHJP), a partnership between the Yale schools of public health and law, co-authored a previous report in 2013 about the role of the United Nations in causing the cholera epidemic in Haiti. The 58-page report, titled “Peacekeeping without Accountability,” examined the U.N. role in precipitating the crisis and the U.N.’s responsibilities to provide legal remedies to victims of the epidemic. The GHJP was established in 2012 to promote interdisciplinary, innovative, and effective responses to global health disparities.