Description

Cholera is an acute intestinal infection caused by toxigenic Vibrio cholerae O-group 1 or O-group 139. The infection is often mild and self-limited or subclinical. Severe illness may lead to volume depletion. Even patients with severe cases respond dramatically to simple fluid- and electrolyte-replacement therapy. Infection is acquired primarily by ingesting contaminated water or food; person-to-person transmission is rare.

Treatment

Rehydration is the cornerstone of therapy; antibiotics are adjunct therapy and may decrease fluid requirements and duration of illness. Oral rehydration salts, and when necessary intravenous fluids and electrolytes, if administered in a timely manner and in adequate volumes, will reduce case-fatality rates to well under 1%.

Occurrence

Since 1961, V. cholerae has spread from Indonesia through most of Asia into Eastern Europe and Africa, and from North Africa to the Iberian Peninsula. In 1991, an extensive epidemic began in Peru and spread to neighboring countries in the Western Hemisphere. Although few cases of cholera now occur in the Americas, V. cholerae remains endemic in much of the developing world. In 2005, 131,943 cases from 52 countries were reported to the WHO. Resource-poor areas continue to report the vast majority of cases; nearly 95% of cases were reported from Africa (1,2).

Risk for Travelers

Travelers who follow usual tourist itineraries and who observe food safety recommendations while in countries reporting cholera have virtually no risk. From 1996 through 2005, only 35 confirmed cases of cholera in the U.S. were acquired abroad (3,4). The risk is increased for those who drink untreated water or eat poorly cooked or raw seafood in disease-endemic areas.

There have been two reports of cholera associated with food served on board international flights, most recently in 1992, in the midst of the Latin American epidemic, on a flight from Argentina to Los Angeles (5,6). CDC consequently advised the International Air Transport Association that oral rehydration solutions should be carried on international flights and that certain food items prepared in cities with cholera epidemics should not be served. Airline flights have not been implicated in any subsequent cases of cholera.

Clinical Presentation

Cholera is characterized by acute, profuse watery diarrhea, described as “rice-water stools,” and often vomiting, leading to volume depletion. Signs and symptoms include tachycardia, loss of skin turgor, dry mucous membranes, hypotension, and thirst. If untreated, volume depletion can rapidly lead to hypovolemic shock and death. Additional symptoms, including muscle cramps, are secondary to the resulting electrolyte imbalances.

Prevention

“Boil it, cook it, peel it, or forget it” (7). Travelers to cholera-affected areas should adhere to this adage and avoid eating high-risk foods, especially fish and shellfish. Food that is cooked and served hot, fruits and vegetables peeled by the traveler personally, beverages and ice that are made from boiled or chlorinated water, and carbonated beverages are usually safe (see Chapter 2). Chemoprophylaxis is not indicated. Travelers should never bring perishable seafood back into the United States.

VACCINE

Two oral vaccines are available, only one of which is available outside Vietnam; neither is currently licensed in the United States (1). The manufacture and sale of the only cholera vaccine licensed in the United States (by Wyeth Ayerst) have been discontinued. Because of the low risk of cholera to U.S. travelers and the brief and incomplete immunity that the vaccines confer, vaccination is not currently recommended for U.S. travelers.

Both vaccines available in other countries, Dukoral from SBL Vaccin AB and a variant only available in Vietnam, appear to provide somewhat better immunity and have fewer adverse effects than the previously licensed vaccine (1). However, CDC does not recommend either of these two vaccines for most travelers, nor are they licensed in the United States. Further information on Dukoral can be obtained from SBL Vaccin AB at http://www.sblvaccines.com/ or SBL Vaccin AB, SE-105 21 Stockholm, Sweden, telephone46-8-735 10 00, fax46-8-82 73 04, e-mail: info@sblvaccines.se.

Currently, no country or territory requires vaccination against cholera as a condition for entry. Local authorities, however, may continue to require documentation of this vaccination. In such cases, a single dose of either oral vaccine is sufficient to satisfy local requirements, or the traveler may request a medical waiver from a health-care provider. Travel clinics should be aware of this issue and offer medical waivers, preferably written on physician letterhead stationery.

References

1. World Health Organization. Cholera, 2005. Wkly Epidemiol Rec. 2006;81:297-308.
2. Griffith DC, Kelly-Hope LA, Miller MA. Review of reported cholera outbreaks worldwide, 1995-2005. Am J Trop Med Hyg. 2006;75 973-7.
3. Steinberg EB, Greene KD, Bopp CA, Cameron DN, Wells JG, Mintz ED. Cholera in the United States, 1995-2000: trends at the end of the milennium. J Infect Dis. 2001;184:799-802.
4. CDC. Two cases of toxigenic Vibrio cholerae O1 infection after Hurricanes Katrina and Rita —- Louisiana, October 2005. MMWR Morbid Mortal Wkly Rep. 2006;55(no. MM2):31.
5. Sutton RGA. An outbreak of cholera in Australia due to food served in flight on an international aircraft. J. Hyg. 1974;72:441–51.
6. CDC. Cholera associated with an international airline flight, 1992. MMWR Morbid Mortal Wkly Rep. 1992;41:134–5.
7. Kozicki M, Steffen R, Schar M. “Boil it, cook it, peel it, or forget it”: does this rule prevent travellers’ diarrhoea? Int J Epidemiol. 1985;14:169-72.