ARTICLE - CDC - U.S. CHOLERA OUTBREAK

CDC REPORTS ON U.S. CHOLERA OUTBREAK
(Medscape) - By Emma Hitt, PhD

Since the Haiti cholera epidemic in October 2010, 23 cases of cholera have been reported among people living in 8 states in the United States, representing nearly 4 times the annual average in recent years, according to a new report.

The study, by Anna E. Newton, MPH, from the National Center for Emerging and Zoonotic Infectious Diseases at the Centers for Disease Control and Prevention (CDC), in Atlanta, Georgia, and colleagues, was published in the November issue of Emerging Infectious Diseases.

The current issue of the CDC's monthly peer-reviewed public health journal includes 5 additional research articles on cholera, summarizing the CDC's efforts toward the cholera outbreak in Haiti, as well as the most recent information about the genetic underpinnings of the disease.

According to Dr. Newton and colleagues, in the United States, during 2000 to 2010, the average number of cases of cholera was 6, and of those, 57% had traveled internationally. The current report describes 23 case patients, 22 of whom traveled to the affected areas of Hispaniola.

The first case patient was identified in Florida on January 29, 2011, and had returned from a trip to the Dominican Republic. Among the 23 cases reported by about 9 weeks later, 10 patients resided in Florida, 4 in Massachusetts, 4 in New York City, and 1 patient each in Kansas, Michigan, North Carolina, Virginia, and Texas.

Of the patients, 13 reported recently traveling to Haiti, and 9 to the Dominican Republic. The 1 remaining case patient had not traveled to these areas, but had consumed cooked conch brought to the United States from Haiti by relatives.

Dr. Newton and colleagues pointed out that the "risk for cholera transmission in the United States is low because of improved water and sanitation, and there is no evidence of secondary transmission." They added that, "until cholera in Haiti and Dominican Republic resolves, clinicians, microbiologists, and public health workers in the United States should be prepared for more cases in travelers returning from Hispaniola."

Two other studies published in the journal describe the lessons learned during the public health response to the cholera epidemic in Haiti and the Dominican Republic, and the factors associated with a decreased risk of contracting cholera after the January 2010 Port-au-Prince earthquake.

Public Health Response in Haiti

CDC researchers Jordan W. Tappero, MD, MPH, and Robert V. Tauxe, MD, MPH. summarize the participation in the public health response to the October 2010 cholera outbreak by the CDC and its partners. They also describe the efforts of many organizations in mobilizing resources, training community workers, and educating the public.

"The Haitian epidemic shows that as long as cholera exists anywhere in the world, many who drink untreated water and live in areas of poor sanitation are at risk," the authors note. They add that "the more moderate course of the epidemic in the Dominican Republic and the relative sparing of the [internally displaced person] camps in Haiti illustrate how safer water and better sanitation can prevent transmission."

Risk Factors Associated With Transmission

Stacie E. Dunkle, DVM, MPH, from the CDC, and colleagues also report on the risk factors associated with epidemic cholera in Port-au-Prince. They conducted a case–control study and found that water treatment and hand washing were protective against the spread of cholera in this setting. They also found that a diverse diet, which they say is a "possible proxy for improved nutrition," was protective against cholera.

Transmission and Genetics of Cholera

Three of the 6 papers describe the transmission and genetics of cholera. J. Glenn Morris, Jr, MD, from the University of Florida in Gainesville, proposes a model of transmission for cholera, given a recently described hyperinfectious phase that lasts for several hours after its presence in diarrheal feces. Factors such as changes in temperature during the hyperinfectious phase may then cause rapid and direct person-to-person transmission without transmission of the organism through water consumption.

In a comparative analysis of the genetics of cholera, Aleisha R. Reimer, from the Public Health Agency of Canada, Winnipeg, Manitoba, and colleagues, including CDC researchers, describe how the cholera strain from Haiti seems to be linked to strains previously reported in India and Cameroon

According to the researchers, historically, this strain has been hardy, potent, and drug resistant, and its genetic characteristics indicate that it may easily spread and replace current strains in the Americas.

Finally, a sixth article describes the development of drug-resistant cholera strains in the Haiti outbreak. Maria Sjölund-Karlsson, PhD, from the CDC, and colleagues reported findings from their study of the genetic mechanisms behind this resistance, which indicated that the Haiti strain carries several drug-resistance genes.

"To limit development and spread of antimicrobial drug resistance among [Vibrio cholera], treatment with antimicrobial agents should be restricted to patients with severe dehydration or other conditions that truly warrant their use," the authors conclude.

The studies were not commercially funded. The authors have disclosed no relevant financial relationships.

Emerging Infect Dis. 2011;17.