Potential Bioterrorism Agent: Category B
Also known as: Vibrio cholera, Asiatic cholera and epidemic cholera
Hospital: Report immediately by phone
Lab: Report immediately by phone
Physician: Report immediately by phone
Local Public Health Agency (LPHA): Report immediately by phone; begin active surveillance for additional cases. Iowa Department of Public Health will lead the follow-up investigation.
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
Cholera is an acute watery diarrheal disease caused by enterotoxins produced by Vibrio cholerae bacteria. Two serogroups, O1 and O139, cause extensive epidemics and worldwide pandemics of disease. Non-toxigenic or non-O1, non-O139 V. cholerae infections can cause sporadic illness but do not cause epidemics.
Note: This chapter only pertains to Vibrio cholerae. Other species of Vibrio (e.g., V. parahaemolyticus, V. vulnificus) are not reportable except in outbreak situations.
B. Clinical description
Symptoms: (Mild illness) Infection by 01 or 0139 serogroups of V. cholerae usually results in asymptomatic or mild diarrhea.
Symptoms: (Severe illness) In approximately 1 out of 20 people infected, disease is more severe characterized by profuse watery stools, nausea, some vomiting and muscle cramps.
Complications: Dehydration may develop rapidly and lead to shock and sometimes death within hours. The case-fatality rate in severe untreated cases may exceed 50%; with proper treatment, the rate is less than 1%.
Humans are the primary reservoir although environmental reservoirs exist in brackish or estuarine aquatic environments.
D. Modes of Transmission
V. cholerae is usually transmitted via the ingestion of food or water contaminated (directly or indirectly) by feces or vomitus of infected persons (e.g., via sewage) or by ingestion of raw or undercooked seafood harvested from polluted waters. Large epidemics often related to fecal contamination of water supplies or street vendor foods have been recognized. The disease can spread rapidly in areas with inadequate treatment of sewage and drinking water.
E. Incubation Period
The incubation period ranges from a few hours to 5 days; more commonly within 2 - 3 days.
F. Period of Communicability or Infectious Period
The disease is not likely to spread directly from one person to another as long as standard infection prevention practices are followed; therefore, casual contact with an infected person is not a risk for becoming ill. However, cholera presumably has the potential to be transmitted person to person as long as stools test positive for the bacterium, most likely until a few days after recovery from symptoms. Shedding of bacteria may occasionally persist for several months. Antibiotics effective against the infecting strains shorten the period of communicability.
Since the early 19th century, pandemic cholera has appeared off and on in most parts of the world. Cholera is a major cause of epidemic diarrhea throughout the developing world. There has been an ongoing global pandemic in Asia, Africa and Latin America for the last four decades. In 2009, 45 countries reported 221,226 cholera cases and 4,946 cholera deaths (case-fatality rate 2.24%) to the World Health Organization (WHO). Poor areas continue to report the vast majority of cases; 99% of cases were reported from Africa, continuing a trend.
In the United States, most cases occur among travelers returning from areas experiencing epidemic cholera. Sporadic cases have also occurred among persons ingesting inadequately cooked shellfish harvested from coastal waters along the Texas and Louisiana borders. Currently, most cholera outbreaks have been linked to the El Tor biotype. Studies show that some protection against biotypes (strains) within a serogroup is conferred from previous infection. No protection, however, results from infection with O1 serogroup against O139 serogroup and vice versa.
H. Bioterrorism Potential
Category B Agent: Vibrio cholerae O1 and O139 are identified as a Category B bioterrorism agent, seen particularly as a water safety threat by the CDC. If acquired and properly disseminated, Vibrio cholerae O1 and O139 could cause a serious public health challenge because the bacteria are moderately easy to disseminate, result in moderate morbidity rates and low mortality rates, and require specific enhancements of CDC's diagnostic capacity and enhanced disease surveillance.
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Cholera can be found at: wwwn.cdc.gov/NNDSS/script/casedefDefault.aspx
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
American Academy of Pediatrics. 2003 Red Book: Report of the Committee on Infectious Diseases, 26th Edition. Illinois, American Academy of Pediatrics, 2003.
CDC Website. Cholera Division of Bacterial and Mycotic Diseases. Available at: www.cdc.gov/cholera/index.html
Heymann, D.., ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.
Tauxe, R., Mintz, E., Quick, R. Epidemic Cholera in the New World: Translating Field Epidemiology into New Prevention Strategies. Emerging Infectious Diseases, 1995; 1:4, pp. 141-146.