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The spread of cholera in the midst of an epidemic is largely driven by direct transmission from person to person, although it is well-recognized that Vibrio cholerae is also capable of growth and long-term survival in aquatic ecosystems. While prior studies have shown that aquatic reservoirs are important in the persistence of the disease on the Indian subcontinent, an epidemiological view postulating that locally evolving environmental V. cholerae contributes to outbreaks outside Asia remains debated. The single-source introduction of toxigenic V. cholerae O1 in Haiti, one of the largest outbreaks occurring this century, with 812,586 suspected cases and 9,606 deaths reported through July 2018, provided a unique opportunity to evaluate the role of aquatic reservoirs and assess bacterial transmission dynamics across environmental boundaries. To this end, we investigated the phylogeography of both clinical and aquatic toxigenic V. cholerae O1 isolates and show robust evidence of the establishment of aquatic reservoirs as well as ongoing evolution of V. cholerae isolates from aquatic sites. Novel environmental lineages emerged from sequential population bottlenecks, carrying mutations potentially involved in adaptation to the aquatic ecosystem. Based on such empirical data, we developed a mixed-transmission dynamic model of V. cholerae , where aquatic reservoirs actively contribute to genetic diversification and epidemic emergence, which underscores the complexity of transmission pathways in epidemics and endemic settings and the need for long-term investments in cholera control at both human and environmental levels., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

Cholera is an ancient disease that remains a public health problem in many impoverished locations around the world. Seven pandemics of cholera have been recorded since the first pandemic in 1817, the last of which is on going. Overcrowding, poverty, insufficient water and sanitation facilities increase the risk for cholera outbreaks. The epidemiology of cholera in the areas in Asia, Africa and the Americas where the disease occurs continues to evolve., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Cholera has been eliminated as a public health problem in high-income countries that have implemented sanitation system separating the community's fecal waste from their drinking water and food supply. These expensive, highly-engineered systems, first developed in London over 150 years ago, have not reached low-income high-risk communities across Asia. Barriers to their implementation in communities at highest risk for cholera include the high capital and operating costs for this technological approach, limited capacity and perverse incentives of local governments, and a decreasing availability of water. Interim solutions including household level water treatment, constructing latrines and handwashing promotion have only marginally reduced the risk of cholera and other fecally transmitted diseases. Increased research to develop and policy flexibility to implement a new generation of solutions that are designed specifically to address the physical, financial and political constraints of low-income communities offers the best prospect for reducing the burden of cholera across Asia., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: The economic burden data can provide a basis to inform investments in cholera control and prevention activities. However, treatment costs and productivity loss due to cholera are not well studied., Methods: We included Asian countries that either reported cholera cases to the World Health Organization (WHO) in 2015 or were considered cholera endemic in 2015 global burden of disease study. Public health service delivery costs for hospitalization and outpatient costs, out-of-pocket costs to patients and households, and lost productivity were extracted from literature. A probabilistic multivariate sensitivity analysis was conducted for key outputs using Monte Carlo simulation. Scenario analyses were conducted using data from the WHO cholera reports and conservative and liberal disease burden estimates., Results: Our analysis included 14 Asian countries that were estimated to have a total of 850,000 cholera cases and 25,500 deaths in 2015 While, the WHO cholera report documented around 60,000 cholera cases and 28 deaths. We estimated around $20.2 million (I$74.4 million) in out-of-pocket expenditures, $8.5 million (I$30.1 million) in public sector costs, and $12.1 million (I$43.7 million) in lost productivity in 2015. Lost productivity due to premature deaths was estimated to be $985.7 million (I$3,638.6 million). Our scenario analyses excluding mortality costs showed that the economic burden ranged from 20.3% ($8.3 million) to 139.3% ($57.1 million) in high and low scenarios when compared to the base case scenario ($41 million) and was least at 10.1% ($4.1 million) when estimated based on cholera cases reported to WHO., Conclusion: The economic burden of cholera in Asia provides a better understanding of financial offsets that can be achieved, and the value of investments on cholera control measures. With a clear understanding of the limitations of the underlying assumptions, the information may be used in economic evaluations and policy decisions., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Although much focus is placed on cholera epidemics, the greatest burden occurs in settings in which cholera is endemic, including areas of South Asia, Africa and now Haiti 1,2 . Dhaka, Bangladesh is a megacity that is hyper-endemic for cholera, and experiences two regular seasonal outbreaks of cholera each year 3 . Despite this, a detailed understanding of the diversity of Vibrio cholerae strains circulating in this setting, and their relationships to annual outbreaks, has not yet been obtained. Here we performed whole-genome sequencing of V. cholerae across several levels of focus and scale, at the maximum possible resolution. We analyzed bacterial isolates to define cholera dynamics at multiple levels, ranging from infection within individuals, to disease dynamics at the household level, to regional and intercontinental cholera transmission. Our analyses provide a genomic framework for understanding cholera diversity and transmission in an endemic setting.

Shanchol™, a WHO-prequalified oral cholera vaccine (OCV), has been used to control endemic cholera in Asia, as well as in emergencies and outbreaks elsewhere. The vaccine has not been used by public health systems in cholera-endemic settings of Africa although several outbreak response campaigns have been conducted. Here we present experiences from a mass vaccination campaign in a cholera-endemic setting of Ethiopia in which Shanchol™ was introduced through the public health system. The vaccination site was selected based on cholera cases reported in previous years. Social mobilization involved sensitization of community leaders, household visits, and mass distribution of banners, posters and leaflets. The vaccination was implemented after careful microplanning of logistics and cold chain, manpower, transportation, vaccine supply and supervision and monitoring of adverse events. Vaccine administration was recorded on individual vaccination cards. Vaccine delivery costs were collected and analyzed after vaccination. As there was no experience with Shanchol™ in Ethiopia, a bridging trial was conducted to demonstrate safety and immunogenicity of the vaccine in the local population prior to the mass vaccination. Oral cholera vaccination was conducted in two rounds of four days each in February 2015 and March 2015 in 10 selected villages of Shashemenae rural district of Ethiopia. A total of 62,161 people targeted. 47,137 people (76%) received the first dose, and 40,707 (65%) received two doses. The financial cost of the vaccination campaign was estimated at US $2·60 per dose or US $5·64 per fully immunized person. The cost of vaccine delivery excluding vaccine procurement was $0·68 per dose or $1·48 per fully immunized person. The study demonstrates that mass cholera vaccination administered through the public health system in Ethiopia is feasible, can be implemented through the existing health system at an affordable cost, and the vaccine is acceptable to the community. The lessons from this study are useful for deploying OCV in other African endemic settings through the public health system and may guide future immunization policy decisions.

Vibrio cholerae has caused massive outbreaks and even trans-continental epidemics. In 2008 and 2010, at least 3 remarkable cholera outbreaks occurred in Hainan, Anhui and Jiangsu provinces of China. To address the possible transmissions and the relationships to the 7th pandemic strains of those 3 outbreaks, we sequenced the whole genomes of the outbreak isolates and compared with the global isolates from the 7th pandemic. The three outbreaks in this study were caused by a cluster of V. cholerae in clade 3.B which is parallel to the clade 3.C that was transmitted from Nepal to Haiti and caused an outbreak in 2010. Pan-genome analysis provided additional evolution information on the mobile element and acquired multiple antibiotic resistance genes. We suggested that clade 3.B should be monitored because the multiple antibiotic resistant characteristics of this clade and the 'amplifier' function of China in the global transmission of current Cholera pandemic. We also show that dedicated whole genome sequencing analysis provided more information than the previous techniques and should be applied in the disease surveillance networks.

US cholera surveillance offers insight into global and domestic trends. Between 2001 and 2011, 111 cases were reported to the Centers for Disease Control and Prevention. Cholera was associated with international travel in 90 (81%) patients and was domestically acquired in 20 (18%) patients; for one patient, information was not available. From January 2001 to October 2010, the 42 (47%) travel-associated cases were associated with travel to Asia. In October 2010, a cholera epidemic started in Haiti, soon spreading to the Dominican Republic (Hispaniola). From then to December 2011, 40 (83%) of the 48 travel-associated cases were associated with travel to Hispaniola. Of 20 patients who acquired cholera domestically, 17 (85%) reported seafood consumption; 10 (59%) ate seafood from the US Gulf Coast. In summary, an increase in travel-associated US cholera cases was associated with epidemic cholera in Hispaniola in 2010-2011. Travel to Asia and consumption of Gulf Coast seafood remained important sources of US cholera cases.

Demand for adequate provision of drinking-water and sanitation facilities to promote public health and economic growth is increasing in the rapidly urbanizing countries of the developing world. With a panel of data on Asia and Africa from 1990 to 2008, associations are estimated between the occurrence of cholera outbreaks, the case rates in given outbreaks, the mortality rates associated with cholera and two disease control mechanisms, drinking-water and sanitation services. A statistically significant and negative effect is found between drinking-water services and both cholera case rates as well as cholera-related mortality rates. A relatively weak statistical relationship is found between the occurrence of cholera outbreaks and sanitation services.

Cholera outbreak following the earthquake of 2010 in Haiti has reaffirmed that the disease is a major public health threat. Vibrio cholerae is autochthonous to aquatic environment, hence, it cannot be eradicated but hydroclimatology-based prediction and prevention is an achievable goal. Using data from the 1800s, we describe uniqueness in seasonality and mechanism of occurrence of cholera in the epidemic regions of Asia and Latin America. Epidemic regions are located near regional rivers and are characterized by sporadic outbreaks, which are likely to be initiated during episodes of prevailing warm air temperature with low river flows, creating favorable environmental conditions for growth of cholera bacteria. Heavy rainfall, through inundation or breakdown of sanitary infrastructure, accelerates interaction between contaminated water and human activities, resulting in an epidemic. This causal mechanism is markedly different from endemic cholera where tidal intrusion of seawater carrying bacteria from estuary to inland regions, results in outbreaks.

Cholera was absent from the island of Hispaniola at least a century before an outbreak that began in Haiti in the fall of 2010. Pulsed-field gel electrophoresis (PFGE) analysis of clinical isolates from the Haiti outbreak and recent global travelers returning to the United States showed indistinguishable PFGE fingerprints. To better explore the genetic ancestry of the Haiti outbreak strain, we acquired 23 whole-genome Vibrio cholerae sequences: 9 isolates obtained in Haiti or the Dominican Republic, 12 PFGE pattern-matched isolates linked to Asia or Africa, and 2 nonmatched outliers from the Western Hemisphere. Phylogenies for whole-genome sequences and core genome single-nucleotide polymorphisms showed that the Haiti outbreak strain is genetically related to strains originating in India and Cameroon. However, because no identical genetic match was found among sequenced contemporary isolates, a definitive genetic origin for the outbreak in Haiti remains speculative.

Vibrio cholera, the causal agent of cholera, also occupies an autochthonous aquatic inhabitant. The current, seventh cholera pandemic is linked to O1 El Tor biotype and O139 serogroups. In the last decades, we have witnessed a shift involving genetically and phenotypically varied pandemic clones in Asia and Africa. Recent comparative genomic studies have identified a large 'mobilome', or composed of mobile genomic islands in V. cholerae. All seventh pandemic isolates have highly related genome sequences, but they can be differentiated by set of these genomic islands. A consequence of the extensive lateral gene transfer is that classically important diagnostic markers, such as serotype and biotype, are not reliable and new methods based on genomic sequences are required., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

During epidemics of cholera in two rural sites (Bakerganj and Mathbaria), a much higher proportion of patients came for treatment with severe dehydration than was seen in previous years. V. cholerae O1 isolated from these patients was found to be El Tor in its phenotype, but its cholera toxin (CT) was determined to be that of classical biotype. Whether the observed higher proportion of severe dehydration produced by the El Tor biotype was due to a shift from El Tor to classical CT or due to other factors is not clear. However, if cholera due to strains with increased severity spread to other areas where treatment facilities are limited, there are likely to be many more cholera deaths.

The review presents data on circulation of antibiotic resistant and susceptible strains of Vibrio cholerae serogroups O1 and O139 isolated from cholera patients and healthy persons as well as from the environment, in Asia, Africa, Australia, and Europe (including New Independent States) during 7th cholera pandemic.

Background: Cholera remains an important public health problem. Yet there are few reliable population-based estimates of laboratory-confirmed cholera incidence in endemic areas around the world., Methods: We established treatment facility-based cholera surveillance in three sites in Jakarta (Indonesia), Kolkata (India), and Beira (Mozambique). The annual incidence of cholera was estimated using the population census as the denominator and the age-specific number of cholera cases among the study cohort as the numerator., Findings: The lowest overall rate was found in Jakarta, where the estimated incidence was 0.5/1000 population/year. The incidence was three times higher in Kolkata (1.6/1000/year) and eight times higher in Beira (4.0/1000/year). In all study sites, the greatest burden was in children under 5 years of age., Conclusion: There are considerable differences in cholera incidence across these endemic areas but in all sites, children are the most affected. The study site in Africa had the highest cholera incidence consistent with a growing impression of the large cholera burden in Africa. Burden estimates are useful when considering where and among whom interventions such as vaccination would be most needed.

Cholera, caused by Vibrio cholerae, erupted globally from South Asia in 7 pandemics, but there were also local outbreaks between the 6(th) (1899-1923) and 7(th) (1961-present) pandemics. All the above are serotype O1, whereas environmental or invertebrate isolates are antigenically diverse. The pre 7th pandemic isolates mentioned above, and other minor pathogenic clones, are related to the 7(th) pandemic clone, while the 6(th) pandemic clone is in the same lineage but more distantly related, and non-pathogenic isolates show no clonal structure. To understand the origins and relationships of the pandemic clones, we sequenced the genomes of a 1937 prepandemic strain and a 6(th) pandemic isolate, and compared them with the published 7(th) pandemic genome. We distinguished mutational and recombinational events, and allocated these and other events, to specific branches in the evolutionary tree. There were more mutational than recombinational events, but more genes, and 44 times more base pairs, changed by recombination. We used the mutational single-nucleotide polymorphisms and known isolation dates of the prepandemic and 7(th) pandemic isolates to estimate the mutation rate, and found it to be 100 fold higher than usually assumed. We then used this to estimate the divergence date of the 6(th) and 7(th) pandemic clones to be about 1880. While there is a large margin of error, this is far more realistic than the 10,000-50,000 years ago estimated using the usual assumptions. We conclude that the 2 pandemic clones gained pandemic potential independently, and overall there were 29 insertions or deletions of one or more genes. There were also substantial changes in the major integron, attributed to gain of individual cassettes including copying from within, or loss of blocks of cassettes. The approaches used open up new avenues for analysing the origin and history of other important pathogens.

The problems of the evolution of cholera at the stages of its pandemic spread are described. A short characterization of endemic zones in the countries of Asia, Africa and Latin America, stipulating the preservation of infection and the appearance of periodic epidemics in the world, is presented. Special attention is paid to the genesis of epidemic outbreaks in endemic and introduced foci of cholera, differing in the specific features of their formation and the accumulation of the epidemic variant of the infective agent in aqueous habitat. The role of the ecosystem of surface water reservoirs in the prolonged survival of cholera vibrios is evaluated. The necessity of the detailed study of the mechanisms and forms of existence of serogroup 0139 vibrio in open water reservoirs is substantiated. In the system of epidemiological surveillance on cholera the microbiological monitoring of environmental objects assumes the leading importance.

Intestinal infection with Vibrio cholerae results in the loss of large volumes of watery stool, leading to severe and rapidly progressing dehydration and shock. Without adequate and appropriate rehydration therapy, severe cholera kills about half of affected individuals. Cholera toxin, a potent stimulator of adenylate cyclase, causes the intestine to secrete watery fluid rich in sodium, bicarbonate, and potassium, in volumes far exceeding the intestinal absorptive capacity. Cholera has spread from the Indian subcontinent where it is endemic to involve nearly the whole world seven times during the past 185 years. V cholerae serogroup O1, biotype El Tor, has moved from Asia to cause pandemic disease in Africa and South America during the past 35 years. A new serogroup, O139, appeared in south Asia in 1992, has become endemic there, and threatens to start the next pandemic. Research on case management of cholera led to the development of rehydration therapy for dehydrating diarrhoea in general, including the proper use of intravenous and oral rehydration solutions. Appropriate case management has reduced deaths from diarrhoeal disease by an estimated 3 million per year compared with 20 years ago. Vaccination was thought to have no role for cholera, but new oral vaccines are showing great promise.

"Mikrob" Russian Research Anti-Plague Institute, Saratov Studies of the genomic evolution of pathogenic bacteria became a priority research trend of modern molecular genetics. Vibrio cholerae, whose pathogenic properties are conditioned by the presence of virulence blocks of differing phylogenetic origins in 2 chromosomes, turned out to be a unique model object for studies of evolutionary transformations of genomes that are causative agents of extra dangerous infections. The molecular-and-genetic mechanisms underlying the change of biovariants and the emergence of a cholera agent of a new serogroup are in the focus of attention. Finally, the possibility that the new V. cholerae pathogenic clone originated due to horizontal genetic transfers and recombination phenomena is under discussion in the survey.

Cholera existed in many parts of the world since olden days. Gangetic delta is considered as the home of the disease. Since 1970 there has been a significant development of the disease with its ecologic and epidemiologic aspects. Vibrio cholerae non-01 strain in taxonomically separated from V cholerae 01 strain. Though 01 strain causes epidemic outbreaks, still non-01 has been implicated to cause cholera like illness. While humans are long considered to be the only reservoir of V cholerae 01 strain, but the organism appears to have a free-living cycle in the natural environment. The organism survives more rapidly in the brackish water than fresh water. It has been demonstrated that V cholerae undergoes conversion to a viable but non-culturable state, whereby the cells are reduced in size, become ovoid, but in contrast to starved cells, do not grow at all on standard laboratory media. Seasonality coupled with starvation response and dormancy phenomenon, reflects the origin of V cholerae as an autochthonous estuary dweller. All biotypes of this organism can grow on media containing chitin as the sole carbon source. Outbreaks of the disease are related to plankton blooms associated with warmer sea-surface temperature. In 1997 V cholerae 01 biotype El tor continued to occur in all regions of the world. In 1982 a new classical variant initially displaced entrenched El tor in Bangladesh and coexisted with it for almost a decade. V cholerae 0139 Bangal has arisen along the Bay of Bengal and has spread in Asia.

Cholera has been recognized as a killer disease since earliest time. Since 1817, six pandemics have swept over the world, and the seventh one is in progress. The disease is caused by infection of the small intestine by Vibrio cholerae O1 and O139 and is characterized by massive acute diarrhoea, vomiting, and dehydration: death occurs in severe, untreated cases. Cholera is a highly contagious disease, and is transmitted primarily by ingestion of faecally-contaminated water by susceptible persons. Besides water, foods have also been recognized as an important vehicle for transmission of cholera. Foods are likely to be faecally contaminated during preparation, particularly by infected food handlers in an unhygienic environment. The physicochemical characteristics of foods that support survival and growth of V. cholerae O1 and O139 include high-moisture content, neutral or an alkaline pH, low temperature, high-organic content, and absence of other competing bacteria. Seafoods, including fish, shellfish, crabs, oysters and clams, have all been incriminated in cholera outbreaks in many countries, including the United States and Australia. Contaminated rice, millet gruel, and vegetables have also been implicated in several outbreaks. Other foods, including fruits (except sour fruits), poultry, meat, and dairy products, have the potential of transmitting cholera. To reduce the risk of food-borne transmission of cholera, it is recommended that foods should be prepared, served, and eaten in an hygienic environment, free from faecal contamination. Proper cooking, storing, and re-heating of foods before eating, and hand-washing with safe water before eating and after defaecation are important safety measures for preventing food-borne transmission of cholera.

Objective: To describe US cholera surveillance data from 1992 to 1994 and the domestic impact of the epidemics of Vibrio cholerae O1 in Latin America and V cholerae O139 in Asia., Design, Setting, and Participants: Retrospective review of surveillance data from all cases of cholera reported to the Centers for Disease Control and Prevention (CDC) from January 1, 1992, through December 31, 1994, in the United States and its territories., Main Outcome Measures: Clinical, epidemiologic, and laboratory surveillance data., Results: From 1992 through 1994, 160 cases of cholera were reported to CDC by 20 states and 1 territory. This is a marked increase: only 136 cases were reported from 1965 through 1991. Outbreaks affecting 75 passengers on an airplane from Latin America and 5 passengers on a cruise ship in Southeast Asia accounted for 50 percent of cases. Vibrio cholerae O139 caused 6 cases (4 percent). The proportion of V cholerae O1 isolates resistant to at least 1 antimicrobial agent rose from 3 percent in 1992 to 93 percent in 1994. Of 158 patients whose location of exposure was known, 151 (96 percent) acquired infection abroad (125 in Latin America, 26 in Asia). Of 105 persons whose reason for travel was known, 31 (30 percent) were US residents who had returned to their country of origin to visit family or friends, and 65 (62 percent) were non-US residents visiting the United States from cholera-affected countries. The cholera rate among persons arriving in the United States from cholera-affected regions was 0.27 case per 100000 air travelers, not substantially increased from earlier estimates., Conclusions: Cholera has increased in the United States since 1991, reflecting global changes in cholera epidemiology, and is now primarily travel associated and antimicrobial resistant. Most travelers were not traditional tourists; reaching them with prevention measures may be difficult. The risk of cholera to the individual traveler remains extremely low.

Since October 1992, epidemics of cholera associated with Vibrio cholerae O group 139 have occurred in India, Bangladesh, and much of the rest of Asia. A volunteer model was used to determine the safety, immunogenicity, and efficacy of an attenuated delta ctxA delta zot delta ace delta cep V. cholerae O139 vaccine strain, designated CVD 112. Six volunteers received 10(6) cfu and 6 received 10(8) cfu of CVD 112. No subject who received the 10(6) dose had diarrhea or other severe symptoms after vaccination; 3 vaccinees developed mild diarrhea (mean stool volume, 648 mL) after receiving the higher dose. Five weeks after vaccination, 8 vaccinees and 15 unvaccinated control subjects underwent challenge with 10(6) cfu of wild type V. cholerae O139 AI1837. One vaccinee (13%) and 12 control subjects (80%) developed diarrhea after challenge (P = .003). The short-term protective efficacy conferred by vaccine strain CVD 112 was 84% and was remarkably similar to that conferred by primary wild type clinical infection (80%).

In 1994, Vibrio cholerae O1 biotype El Tor, the agent responsible for the seventh cholera pandemic which began in 1961, continued to spread in all regions of the world (Map 1). In all, 384,403 cholera cases were officially reported to WHO in 1994 (a 2% increase over 1993), reversing the downward trend which started in 1992. A total of 10,692 deaths were reported in 1994, increasing the reported global case-fatality ratio (CFR) to 2.8% from 1.8% in 1993. Cholera cases were notified from 94 countries/areas, the highest number ever reporting in one year. (Table 1 and Fig. 1). The year was marked by the dramatic cholera outbreak that devastated the Rwandan refugee camps in Goma, Zaire in July. Major outbreaks also affected Afghanistan, Brazil, Guinea, Guinea-Bissau and Somalia. Africa reported a rise in the number of cholera cases, and was the continent accounting for the largest proportion of all reported cases. The incidence of cholera cases in the Americas continued to fall and reported CFR was the lowest recorded since the disease reached Latin America in 1991. Asia reported a 17% increase in cholera cases compared with 1993. Europe, which usually reports only imported cases, registered a significant increase in the number of indigenous cholera cases. Oceania reported 6 cases, 5 of which were imported, and no deaths (Figs. 2 and 3). The new V. cholerae strain O139 (Bengal) has affected 10 countries in Asia since it was first detected in India at

The cholera epidemic caused by Vibrio cholerae O1 that began in January 1991 has continued to spread in Central and South America (Figure 1). In southern Asia, the epidemic caused by the newly recognized strain V. cholerae O139 that began in late 1992 also has continued to spread (Figure 2). This report updates surveillance findings for both epidemics.

Only Vibrio cholerae strains of serotype O1 are known to cause epidemics, while non-O1 strains are associated with sporadic cases of cholera. It was therefore unexpected that the recent cholera epidemic in Asia was caused by a non-O1 strain with the serotype O139. We provide evidence that O139 arose from a strain closely related to the causative agent of the present cholera pandemic, V. cholerae O1 El Tor, by acquisition of novel DNA which was inserted into, and replaced part of, the O antigen gene cluster of the recipient strain. Part of the novel DNA was sequenced and two open reading frames (otnA and otnB) were observed, the products of which showed homology to proteins involved in capsule and O antigen synthesis, respectively. This suggests that the otnAB DNA determines the distinct antigenic properties of the O139 cell surface. The otnAB DNA was not detected in O1 strains, but was present in two non-O1 V. cholerae strains with serotypes O69 and O141. In the O69 and O139 strains the otnAB genes were located proximate to the putative insertion sequence (IS) element rfbQRS, which is associated with O antigen synthesis genes in O1 strains, and may have played a role in the insertion of the otnAB DNA in the recipient chromosome. Our results suggest that the O139 strain arose by horizontal gene transfer between a non-O1 and an O1 strain. The acquired DNA has altered the antigenic properties of the recipient O1 strain, providing a selective advantage in a region where a large part of the population is immune to O1 strains.(ABSTRACT TRUNCATED AT 250 WORDS)

The distribution, characterization and function of the tcpA gene was investigated in Vibrio cholerae O1 strains of the El Tor biotype and in a newly emergent non-O1 strain classified as serogroup O139. The V. cholerae tcpA gene from the classical biotype strain O395 was used as a probe to identify a clone carrying the tcpA gene from the El Tor biotype strain E7946. The sequence of the E7946 tcpA gene revealed that the mature El Tor TcpA pilin has the same number of residues as, and is 82% identical to, TcpA of classical biotype strain O395. The majority of differences in primary structure are either conservative or clustered in a manner such that compensatory changes retain regional amino acid size, polarity and charge. In a functional analysis, the cloned gene was used to construct an El Tor mutant strain containing an insertion in tcpA. This strain exhibited a colonization defect in the infant mouse cholera model similar in magnitude to that previously described for classical biotype tcpA mutants, thus establishing an equivalent role for TCP in intestinal colonization by El Tor biotype strains. The tcpA analysis was further extended to both a prototype El Tor strain from the Peru epidemic and to the first non-O1 strain known to cause epidemic cholera, an O139 V. cholerae isolate from the current widespread Asian epidemic. These strains were shown to carry tcpA with a sequence identical to E7946. These results provide further evidence that the newly emergent non-O1 serogroup O139 strain represents a derivative of an El Tor biotype strain and, despite its different LPS structure, shares common TCP-associated antigens.(ABSTRACT TRUNCATED AT 250 WORDS)

In 1992, the seventh pandemic of Vibrio cholerae O1 biotype E1 Tor continued to spread throughout the world. Sixty-eight countries, representing every region, reported 461,783 cases and 8,072 deaths, yielding a global case-fatality rate of 1.7% (Map 1). A decrease was noted in the reported number of cases (22%) and deaths (58%) in 1992 as compared with 1991, but 9 additional countries were affected. All but 2 of the 21 countries in Central and South America were affected. Reports of 354,089 cases (a decrease of 9.5% from 1991), 2,401 deaths (a decrease of 40%), and a case-fatality rate of 0.68% were received from the Region of the Americas. In Africa, 20 of the 52 countries reported 91,081 cases and 5,291 deaths, a decrease of 41% and 62%, respectively, over 1991. The case-fatality rate of 9.1% in 1991 decreased to 5.8% in 1992. The countries of Asia reported 16,299 cases and 372 deaths (decreases of 67% and 71%, respectively), while 296 cases with 8 deaths were notified from Oceania. Europe reported 18 cases, 14 of which were imported (Table 1). On the whole, the cholera situation in the world during 1992 resembled that of the previous year, in terms of geographical occurrence and reported cases, although the substantial decrease in reported mortality is an encouraging development. While the total number of cases remained relatively stable, important new outbreaks occurred in the Americas, against a background of what increasingly appears to be an endemic situation. In Africa, reported case-fatality rates, although substantially lower than in 1991, continue to be disturbingly high.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholera toxin is the principal factor causing the profuse intestinal fluid secretion that is characteristic of cholera. The DNA sequences of the cholera toxin subunit B structural genes from 45 Vibrio cholerae O1 strains isolated in 29 countries over a period of 70 years were determined by automated DNA sequencing of polymerase chain reaction-generated amplicons. Three types of cholera toxin B subunit gene (ctxB) were identified. Genotype 1 was found in strains of classical biotype worldwide and El Tor biotype strains associated with the U.S. Gulf Coast, genotype 2 was found in El Tor biotype strains from Australia, and genotype 3 was found in El Tor biotype strains from the seventh pandemic and the recent Latin American epidemic. All base changes correspond to an amino acid substitution in the B subunit of the cholera toxin. Heterogenicity in the B subunit could have implications for vaccine development and diagnostic tests for cholera toxin and antitoxin. We conclude that this technology provides timely and potentially useful epidemiological information.