Cholera in Mexico
By Amesh A. Adalja, MD, FACP, FACEP, November 8, 2013
There have been 7 distinct cholera pandemics during the last 2 centuries, each caused by a different strain of V. cholerae. The current pandemic, caused by the O1 El Tor biotype, has been occurring since 1961.1 The ongoing cholera O1 epidemic in Haiti, which has caused more than 600,000 cases and 8,000 fatalities to date, has prompted concern about wider spread of this bacterium into the Western Hemisphere, particularly now that cases linked to Haiti have been detected in the US, Cuba, and the Dominican Republic.2 Mexico, the most recent nation to face imported cholera has reported 176 cases, 57 of which were hospitalized.2 This is the first local transmission of cholera in Mexico since the 1991-2001 epidemic and has been linked to the Haitian strain.2
Toxin Mediated Disease
Following a 12- to 72-hour incubation period, infection with V. cholerae causes severe watery diarrhea ("rice water") caused by the action of the cholera toxin that binds to cells lining intestinal mucosa. The toxin is present in all strains of pathogenic V. cholerae species. The action of the toxin increases concentrations of cAMP, blocking intestinal absorption of sodium and chloride and promoting the secretion of water and chloride by the crypt cells of the intestine. This produces the voluminous diarrhea of cholera. Diagnosis is usually made based on clinical suspicion coupled with stool culture or serology.1
Relatively Simple Treatment
The primary treatment is fluid replacement. The mainstays of fluid resuscitation are oral rehydration solution (ORS) or IV lactated ringer's solution. Antimicrobial therapy as an adjunct to fluid resuscitation has been shown to decrease the diarrhea duration and stool volume by approximately 50%. Antibiotics with activity against V. cholerae include tetracyclines, macrolides, fluoroquinolones, and trimethoprim-sulfamethaxazole. However, resistance to tetracyclines and fluoroquinolones has been detected. Other adjuncts include oral zinc supplementation. Zinc is essential to the function of many enzymes, including those responsible for regeneration of intestinal epithelium, and is depleted in patients with severe diarrhea. There is no FDA-approved vaccine against cholera, though vaccines are available and used widely internationally.
Outbreaks in the US
Each year, cholera cases linked to travel to an endemic region or domestic seafood and/or water exposure are diagnosed within the US. In 2009, prior to the Haitian outbreak, 12 cases occurred in the US and were of the O1, O139, O75, and O141 serogroups.3 In 2011, the last year for which surveillance data is available, there were a total 55 cases of cholera 42 O1 in the US. The vast majority of serogroup O1 cases were travel-related, with many patients linked to Haiti or the Dominican Republic.4 Additionally, an 11-person domestic outbreak of the O75 strain occurred in 2011 and was linked to consumption of raw or undercooked oysters from a specific harvest region.
With cholera now endemic in Haiti and cases occurring as close as Mexico, Cuba, and the DR, physicians should be on alert for patients infected with this bacterium and initiate treatment rapidly when clinically suspicious cases present.
- Seas C, Gutuzzo E. Vibrio cholerae. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, PA: Churchill Livingstone; 2010.
- Cholera in Mexico--update. WHO. October 28, 2013. http://www.who.int/csr/don/2013_10_28/en. Accessed November 6, 2013.
- National enteric disease surveillance: COVIS annual summary, 2009. CDC. http://www.cdc.gov/nationalsurveillance/PDFs/CSTEVibrio2009.pdf. Accessed November 6, 2013.
- National enteric disease surveillance: COVIS annual summary, 2011. CDC. http://www.cdc.gov/ncezid/dfwed/PDFs/covis-annual-report-2011-508c.pdf. Accessed November 6, 2013.