CDC Announces Laboratory Test Results of Cholera Outbreak Strain in Haiti

The Haitian Ministry of Public Health and Population has received the results of laboratory testing showing that the cholera strain linked to the current outbreak in Haiti is most similar to cholera strains found in South Asia. More information about this strain, including the possibility that it might be found in other regions of the world, is anticipated from additional studies. The findings were reported as part of laboratory collaboration between the National Public Health Laboratory (NPHL) in Haiti and the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta.

The rapid identification of the outbreak strain as Vibrio cholerae serogroup O1, serotype Ogawa and antimicrobial susceptibility profiles were reported last week by the NPHL. The new findings from CDC's laboratory are based on a method of "DNA fingerprinting" called pulsed field gel electrophoresis (PFGE), which analyzes DNA patterns that can then be compared with PFGE patterns of cholera strains from other regions of the world. The PFGE testing was performed on 13 bacterial isolates recovered from patients with cholera in Haiti. The PFGE analysis shows that these isolates are identical, indicating that they are the same strain and similar to a cholera strain found in South Asia.

The lab findings are not unexpected and provide information about the relatedness of the cholera outbreak strain to strains found elsewhere in the world.

"Although these results indicate that the strain is non-Haitian, cholera strains may move between different areas due to global travel and trade," says minister of health Dr. Alex Larsen. "Therefore, we will never know the exact origin of the strain that is causing the epidemic in Haiti. This strain was transmitted by contaminated food or water or an infected person."

Global travel and trade provide many opportunities for infectious diseases such as cholera to spread from one country to another. In most instances, cholera does not spread widely within a country if drinking water and sewage treatment are adequate. When water and sewage treatment is inadequate, as in post-earthquake Haiti, cholera can spread rapidly.

Current preventive measures being used to control the outbreak include treating ill people with oral rehydration solution, providing access to safe water, and encouraging good hygiene and sanitation practices. The Haitian Ministry of Public Health and Population is leading a response that prioritizes measures to protect families at the community level, strengthen primary health care centers already operating across the nation, and establish a network of special cholera treatment centers and designated hospitals for treatment of severe cases.

In the coming weeks, additional laboratory testing, including whole genome DNA sequencing will be conducted, but investigating officials note that such testing may never fully explain how cholera was introduced into Haiti.

"Our primary focus here is to save lives and control the spread of disease," says CDC medical epidemiologist Dr. Jordan Tappero, who is leading the CDC cholera response team in Haiti. "We realize that it's also important to understand how infectious agents move to new countries. However, we may never know the actual origin of this cholera strain."

CDC, in collaboration with the U.S. government through U.S. Agency for International Development, is assisting the government of Haiti, the Pan American Health Organization, and several other international health agencies in this outbreak.