in the infected person and allowing the bacteria to colonize the intestine. current research aims at discovering "the signal that makes the cholera bacteria stop swimming and start to colonize (that is, adhere to the cells of) the small intestine." genetic structure main article: vibrio cholerae amplified fragment length polymorphism fingerprinting of the pandemic isolates of v. cholerae has revealed variation in the genetic structure. two clusters have been identified: cluster i and cluster ii. for the most part, cluster i consists of strains from the 1960s and 1970s, while cluster ii largely contains strains from the 1980s and 1990s, based on the change in the clone structure. this grouping of strains is best seen in the strains from the african continent. antibiotic resistance in many areas of the world, antibiotic resistance is increasing within cholera bacteria. in bangladesh, for example, most cases are resistant to tetracycline, trimethoprim-sulfamethoxazole, and erythromycin. rapid diagnostic assay methods are available for the identification of multi-drug resistant cases. new generation antimicrobials have been discovered which are effective against cholera bacteria in in vitro studies. diagnosis a rapid dipstick test is available to determine the presence of v. cholerae. in those samples that test positive, further testing should be done to determine antibiotic resistance. in epidemic situations, a clinical diagnosis may be made by taking a patient history and doing a brief examination. treatment via hydration and over-the-counter hydration solutions can be started without or before confirmation by laboratory analysis, especially where cholera is a common problem. stool and swab samples collected in the acute stage of the disease, before antibiotics have been administered, are the most useful specimens for laboratory diagnosis. if an epidemic of cholera is suspected, the most common causative agent is v. cholerae o1. if v. cholerae serogroup o1 is not isolated, the laboratory should test for v. cholerae o139. however, if neither of these organisms is isolated, it is necessary to send stool specimens to a reference laboratory. infection with v. cholerae o139 should be reported and handled in the same manner as that caused by v. cholerae o1. the associated diarrheal illness should be referred to as cholera and must be reported in the united states. prevention preventive inoculation against cholera in 1966 the world health organization (who) recommends focusing on prevention, preparedness, and response to combat the spread of cholera. they also stress the importance of an effective surveillance system. governments can play a role in all of these areas. water, sanitation and hygiene further information: wash § health aspects although cholera may be life-threatening, prevention of the disease is normally straightforward if proper sanitation practices are followed. in developed countries, due to their nearly universal advanced water treatment and sanitation practices, cholera is rare. for example, the last major outbreak of cholera in the united states occurred in 1910–1911. cholera is mainly a risk in developing countries in those areas where access to wash (water, sanitation and hygiene) infrastructure is still inadequate. effective sanitation practices, if instituted and adhered to in time, are usually sufficient to stop an epidemic. there are several points along the cholera transmission path at which its spread may be halted: sterilization: proper disposal and treatment of all materials that may have come into contact with the feces of other people with cholera (e.g., clothing, bedding, etc.) are essential. these should be sanitized by washing in hot water, using chlorine bleach if possible. hands that touch cholera patients or their clothing, bedding, etc., should be thoroughly cleaned and disinfected with chlorinated water or other effective antimicrobial agents. sewage and fecal sludge management: in cholera-affected areas, sewage and fecal sludge need to be treated and managed carefully in order to stop the spread of this disease via human excreta. provision of sanitation and hygiene is an important preventative measure. open defecation, release of untreated sewage, or dumping of fecal sludge from pit latrines or septic tanks into the environment need to be prevented. in many cholera affected zones, there is a low degree of sewage treatment. therefore, the implementation of dry toilets that do not contribute to water pollution, as they do not flush with water, may be an interesting alternative to flush toilets. sources: warnings about possible cholera contamination should be posted around contaminated water sources with directions on how to decontaminate the water (boiling, chlorination etc.) for possible use. water purification: all water used for drinking, washing, or cooking should be sterilized by either boiling, chlorination, ozone water treatment, ultraviolet light sterilization (e.g., by solar water disinfection), or antimicrobial filtration in any area where cholera may be present. chlorination and boiling are often the least expensive and most effective means of halting transmission. cloth filters or sari filtration, though very basic, have significantly reduced the occurrence of cholera when used in poor villages in bangladesh that rely on untreated surface water. better antimicrobial filters, like those present in advanced individual water treatment hiking kits, are most effective. public health education and adherence to appropriate sanitation practices are of primary importance to help prevent and control transmission of cholera and other diseases. handwashing with soap or ash after using a toilet and before handling food or eating is also recommended for cholera prevention by who africa. dumping of sewage or fecal sludge from a un camp into a lake in the surroundings of port-au-prince is thought to have contributed to the spread of cholera after the haiti earthquake in 2010, killing thousands. example of a urine-diverting dry toilet in a cholera-affected area in haiti. this type of toilet stops transmission of disease via the fecal-oral route due to water pollution. cholera hospital in dhaka, showing typical "cholera beds". surveillance surveillance and prompt reporting allow for containing cholera epidemics rapidly. cholera exists as a seasonal disease in many endemic countries, occurring annually mostly during rainy seasons. surveillance systems can provide early alerts to outbreaks, therefore leading to coordinated response and assist in preparation of preparedness plans. efficient surveillance systems can also improve the risk assessment for potential cholera outbreaks. understanding the seasonality and location of outbreaks provides guidance for improving cholera control activities for the most vulnerable. for prevention to be effective, it is important that cases be reported to national health authorities. vaccination main article: cholera vaccine euvichol-plus oral vaccine for cholera spanish physician jaume ferran i clua developed a cholera inoculation in 1885, the first to immunize humans against a bacterial disease. however, his vaccine and inoculation was rather controversial and was rejected by his peers and several investigation commissions. russian-jewish bacteriologist waldemar haffkine successfully developed the first human cholera vaccine in july 1892. he conducted a massive inoculation program in british india. persons who survive an episode of cholera have long-lasting immunity for at least 3 years (the period tested.) a number of safe and effective oral vaccines for cholera are available. the world health organization (who) has three prequalified oral cholera vaccines (ocvs): dukoral, sanchol, and euvichol. dukoral, an orally administered, inactivated whole cell vaccine, has an overall efficacy of about 52% during the first year after being given and 62% in the second year, with minimal side effects. it is available in over 60 countries. however, it is not currently recommended by the centers for disease control and prevention (cdc) for most people traveling from the united states to endemic countries. the vaccine that the us food and drug administration (fda) recommends, vaxchora, is an oral attenuated live vaccine, that is effective for adults aged 18–64 as a single dose. one injectable vaccine was found to be effective for two to three years. the protective efficacy was 28% lower in children less than five years old. however, as of 2010, it has limited availability. work is under way to investigate the role of mass vaccination. the who recommends immunization of high-risk groups, such as children and people with hiv, in countries where this disease is endemic. if people are immunized broadly, herd immunity results, with a decrease in the amount of contamination in the environment. who recommends that oral cholera vaccination be considered in areas where the disease is endemic (with seasonal peaks), as part of the response to outbreaks, or in a humanitarian crisis during which the risk of cholera is high. oral cholera vaccine (ocv) has been recognized as an adjunct tool for prevention and control of cholera. the world health organization (who) has prequalified three bivalent cholera vaccines—dukoral (sbl vaccines), containing a non-toxic b-subunit of cholera toxin and providing protection against v. cholerae o1; and two vaccines developed using the same transfer of technology—shanchol (shantha biotec) and euvichol (eubiologics co.), which have bivalent o1 and o139 oral killed cholera vaccines. oral cholera vaccination could be deployed in a diverse range of situations from cholera-endemic areas and locations of humanitarian crises, but no clear consensus exists. sari filtration women at a village pond in matlab, bangladesh washing utensils and vegetables. the woman on the right is putting a sari filter onto a water-collecting pot (or kalash) to filter water for drinking. developed for use in bangladesh, the "sari filter" is a simple and cost-effective appropriate technology method for reducing the contamination of drinking water. used sari cloth is preferable but other types of used cloth can be used with some effect, though the effectiveness will vary significantly. used cloth is more effective than new cloth, as the repeated washing reduces the space between the fibers. water collected in this way has a greatly reduced pathogen count—though it will not necessarily be perfectly safe, it is an improvement for poor people with limited options. in bangladesh this practice was found to decrease rates of cholera by nearly half. it involves folding a sari four to eight times. between uses the cloth should be rinsed in clean water and dried in the sun to kill any bacteria on it. a nylon cloth appears to work as well but is not as affordable. treatment cholera patient being treated by oral rehydration therapy in 1992 continued eating speeds the recovery of normal intestinal function. the who recommends this generally for cases of diarrhea no matter what the underlying cause. a cdc training manual specifically for cholera states: "continue to breastfeed your baby if the baby has watery diarrhea, even when traveling to get treatment. adults and older children should continue to eat frequently." fluids the most common error in caring for patients with cholera is to underestimate the speed and volume of fluids required. in most cases, cholera can be successfully treated with oral rehydration therapy (ort), which is highly effective, safe, and simple to administer. rice-based solutions are preferred to glucose-based ones due to greater efficiency. in severe cases with significant dehydration, intravenous rehydration may be necessary. ringer's lactate is the preferred solution, often with added potassium. large volumes and continued replacement until diarrhea has subsided may be needed. ten percent of a person's body weight in fluid may need to be given in the first two to four hours. this method was first tried on a mass scale during the bangladesh liberation war, and was found to have much success. despite widespread beliefs, fruit juices and commercial fizzy drinks like cola are not ideal for rehydration of people with serious infections of the intestines, and their excessive sugar content may even harm water uptake. if commercially produced oral rehydration solutions are too expensive or difficult to obtain, solutions can be made. one such recipe calls for 1 liter of boiled water, 1/2 teaspoon of salt, 6 teaspoons of sugar, and added mashed banana for potassium and to improve taste. electrolytes as there frequently is initially acidosis, the potassium level may be normal, even though large losses have occurred. as the dehydration is corrected, potassium levels may decrease rapidly, and thus need to be replaced. this may be done by consuming foods high in potassium, like bananas or coconut water. antibiotics antibiotic treatments for one to three days shorten the course of the disease and reduce the severity of the symptoms. use of antibiotics also reduces fluid requirements. people will recover without them, however, if sufficient hydration is maintained. the who only recommends antibiotics in those with severe dehydration. doxycycline is typically used first line, although some strains of v. cholerae have shown resistance. testing for resistance during an