Epidemiology of The Cholera Epidemic in Haiti

Overview

Cholera is an acute diarrheal disease caused by Vibrio Cholerae bacterium, transmitted via ingestion of contaminated water or food. Worldwide it is estimated to each year cause between 1, 3 to 4 million cases, and between 21000 to 143000 deaths. In 2016, 54% of cases were reported from Africa, 13% from Asia and 32% from Hispaniola (Dominican Republic and Haiti). Most infected will have a mild disease or even asymptomatic. These cases are easily treated with oral rehydration solution. Severe cases occur in those that become severely dehydrated, becoming at risk of shock. In such cases prompt volume resuscitation is needed and antibiotics should be provided to reduce duration of diarrhoea, to reduce volume of rehydration needed and to decrease the amount of V. cholerae excreted in stool.

The Cholera outbreak of Haiti emerged in October of 2010, in the aftermath of the January 2010 earthquake. This natural disasters effect on the country´s already strained healthcare and sanitary infrastructure, added to the influx of foreign aid workers from regions with endemic cholera outbreaks are believed to be important factors of its emergence in Haiti.

Results

The data shows that since the emergence of Cholera in Haiti in October 2010, there has been a total of 819, 000 suspected cases and 9, 769 total deaths as of May 2018. This makes it the largest modern outbreak of Cholera, until it was surpassed by the 2016-2017 Yemen outbreak, although it is still the most deadly modern outbreak. The incidence in Haiti has been steadily decreasing in the past years, but although national and WHO measures are in place, eradication has not yet been accomplished. Studies examining the DNA fingerprinting and genotyping of the isolated V. Cholera in Haiti combined with the correlation of the arrival of a Nepalese UN battalion with the time and place of the outbreak makes it possible to conclude that the strain was likely imported and released into the environment by the mentioned UN contingent. This was denied by the UN for several years, until they issued an apology in 2016.

Discussion

Epidemiological studies, local observations and genetic studies of the Cholera strains all point to the most likely cause of the epidemic being the introduction of the pathogen into the environment by the Nepalese UN battalion. Interestingly, the UN denied this fact for over 5 years, and produced their own report about the outbreak and its origins. Having not gone as far as gathering information about the credentials, independence or objectivity of the researchers behind this report, any statements regarding the basis of their approach is impossible. However, it does seem that its conclusions may lack validity, seeing as virtually all other research in the matter has come to a different conclusion. The organizations denial and response has been criticized, and perhaps rightfully so seeing as the UN has a history of denial in a similar situation, during the Kosovo conflict.

Vibrio cholera is a comma-shaped gram-negative rod. They are highly motile organisms that exists naturally in aquatic environments. It is a diverse species that include pathogenic and non-pathogenic variants, only cholera-toxin producing strains are capable of causing Cholera. Classification is done according to structure of the O-antigen of its lipopolysaccharide. More than 200 serogroups have been reported, but only serogroups O1 and O139 have been associated with large scale epidemics. V. cholera O1 is the cause of the current global pandemic and it can be divided into two biotypes, El Tor and classical.

In order for infection to occur, V. cholerae must survive the acidic environment of the stomach, colonize the small intestine, and produce the cholera toxin that causes massive fluid secretion into small intestine.

Epidemiology

Cholera is assumed to be vastly underreported, but there is an estimated 1, 3 to 4 million cases, and between 21000 to 143000 deaths attributed to V. Cholerae annually. It primarily affects resource-limited regions with inadequate access to clean water sources. In 2016, 54% of cases were reported from Africa, 13% from Asia and 32% from Hispaniola (Dominican Republic and Haiti). Cholera is endemic to approx. 50 countries, mostly in Africa and Asia. Epidemics have occurred throughout Africa, Asia, the Middle East, and Americas, and can be particularly extensive. As an example, the strain seen in the Haiti epidemic has been subsequently associated with outbreaks in neighboring countries of Dominican Republic, Cuba and Mexico.

Patterns of infection and transmission generally differs between areas that are historically endemic or epidemic. Areas of high endemicity typically has a seasonal distribution with peaks before and after rainy seasons, and highest incidence occurring in children younger than five, reflecting a lack of immunity in children. In areas of high epidemicity there is more limited immunity in the population as a whole, reflected in the more similar incidence in adults and children. However, in endemic regions there may be superimposed epidemics. An example is the devastated infrastructure in Yemen after years of warfare, which led to two sequential outbreaks in 2016 and 2017. The second of these outbreaks led to the worst cholera outbreak to date, with approx. 500. 000 cases and 2000 associated fatalities within just four months.

The transmission of V. cholera is primarily via the ingestion of contaminated food or water. Water is an important reservoir in endemic regions, and because the bacteria can live on plankton, filtration of water is important to reduce incidence. It is thought that in epidemics, the person-to-person transmission of hyperinfectious V. cholera is essential in the rapid propagation.

Clinical presentation

Cholera is a disease that is can be extremely virulent. In most cases, the presentation is mild or asymptomatic. It has an incubation period of one to two days typically. The classical presentation is voluminous watery (rice-water) stool. It may have a typical fishy odor. The diarrhea is usually painless without tenesmus, and may reach an output of as much as 1L per hour in severe cases. Vomiting and abdominal discomfort also may occur, but fever is uncommon. May be indistinguishable from other types of gastroenteritis.

In severe disease, rapid hypovolemia and electrolyte loss is a feared result, and in fatalities there has been reported an median time between onset of symptoms to death of about 12 hours. Approximately 5% of patients develop the severe course of the disease.

In mild to moderate disease, oral rehydration solution (ORS) is the gold standard, and can successfully treat about 80% of cases of cholera. In mild disease, the administrated volume should be equal to the assessed volume loss. In moderate disease, adults should be administered between 2200-4000ml in the first 4 hours. In severe disease, rehydration occurs in two phases: IV rehydration and ORS. IV rehydration in accomplished using Ringer’s lactate at the rate of 50ml per kg the first hour, then lowered. The ORS should be started as soon as the patient is able to drink. Antibiotics is indicated in severe cases, to decrease the duration of vomiting, the amount of rehydration needed and to reduce the amount of V. cholera shed in stool.

Origins of the Haiti epidemic

On the 12th of January 2010, the earthquake and humanitarian disaster occurred causing between 100, 000 to 316, 000 casualties and devastating public infrastructure such as sewage and drinking water, already lacking prior to the natural disaster. On October 19th, reports of unusually high incidence of patients with acute watery diarrhea and dehydration are received by the Haitian Ministry of Public Health and Population (MSPP). Vibrio cholera serogroup O1, serotype Ogawa and of biotype El Tor is isolated from specimens. The cases were first reported from the Arbonite and central departments, but cases were occurring in 7 out of 10 departments and in the Capital of Port Au Prince by mid-November. By this time there were 16, 111 persons hospitalized with acute watery diarrhea and 992 cholera deaths reported.

An effort to identify the origins of the outbreak was quickly mounted, as there had not been a Cholera epidemic in Haiti in the previous century although isolated outbreaks in other countries of the Americas had been observed. Initially, the earthquake was theorized to be the cause of the outbreak, but eventually rumors surfaced of a Nepalese contingent of the UN having imported the epidemic. This contingent arrived from the 8th of October, and underwent medical examination before departure. However, stool samples were only acquired when clinically indicated and it is noted in the UN report that there were no cases of diarrhea before or during this contingents tenure in Haiti. The UN camp in question was located close to the village of Meille, along a stream that empty into Artibonite river. Cases of the disease started to appear downstream in the Arbonite river delta, presumably fascilitated by the fact that this river has been known to be used for bathing and as drinking water for villages along its path, in addition to irrigation in agriculture. The UN has blamed an independent contractor for inadequately removing sewage, but there should also be mentioned that Haitian epidemiologists observed several sanitary deficiencies in the UN camp, including a pipe discharging sewage into the river.

It is believed that the first case of the Haitian cholera epidemic was a 28 year old man of the town Mirebalais. He was reported to have had an untreated psychiatric illness for years, and despite having access to clean water at his home, he was reportedly commonly seen walking nude through the town during the day, and be both bathing and drinking from the Latem river. This river is fed by the Meye river, believed to be the source of the cholera outbreak. On 12th of October 2010 this man developed profuse watery diarrhea, and was attempted to be treated conservatively with oral fluids by his family at his home. They did not seek medical attention, and the man died less than 24 hours after the onset of symptoms. Two persons preparing this man for his wake reportedly also developed watery diarrhea. The first hospitalized case of cholera occurred in Mirebalais on the 17th of October 2010.

Compared to the capital city of Port-au-Prince, with 3 million of the country´s total population of 10 million, Mirebalais is a small town with 90% unemployment. In the time period of the epidemics beginning, there were only unpaved roads and the town was largely isolated from the rest of the country. This can explain why it took time to mount any response to the epidemic that stemmed from this area, as it wasn’t exactly an area focused upon.

The progression of the epidemic

On the 18th of October, a Cuban medical brigade reported a large increase in acute watery diarrhea to the Haitian health authorities, with a total of 61 treated cases in the preceding week in Mirebalais. On this very same day, the situation worsened with 28 new admissions and 2 deaths. In this same time-period the water systems of the Mirebalais town were being repaired, and the inhabitants were using the river as a water source. It should also be noted that prisoners drank water from the river downstream from Meille. 34 cases and 4 deaths were recorded in this prison with no other probable cause discovered. On the 31st of October the sanitary deficiencies of the UN camp were resolved, and the incidence in Mirebalais started to decrease.

Prior to 19th of October there were no recorded cases in the lower Artibonite. On this same day, 3 children died of acute watery diarrhea and by the 31st of October there were 3020 cases and 129 deaths recorded. While not directly connected to the Artibonite river, the epidemic also spread to the capitol of Port-au-Prince. Here, the epidemic had two phases. As cases where arriving from the Artibonite delta to Port-au-Prince from October 22nd through November 5th, the incidence were quite moderate with only 76 daily cases on average. Then, there were an explosion in cases mostly occurring in Cite-Soleil, a slum area of the city. Despite this, the incidence was considerably lower than in other parts of Haiti [(0. 51% until November 30, compared with 2. 67% in Artibonite, 1. 86% in Centre, 1. 4% in North-West, and 0. 89% in North) and equally the cholera-related mortality rate (0. 8 deaths/10, 000 persons in Port-au-Prince, compared with 5. 6/10, 000 in Artibonite, 2/10, 000 in Centre, 3. 2/10, 000 in North, and 2. 8/10, 000 in North-West)].

Initially, the epidemic was spreading quickly with over 285. 000 cases and 4865 deaths by March 2011. By March 2012 there had been in total 531. 000 cases and 7050 deaths since the outbreak, leaving more than 5% of the population affected. There were 112. 076 cases and 894 deaths in 2012. There is a progressive decline in the following years. In 2013 there were 58. 809 cases and 593 deaths. In 2014, from 1st of January to 30th of November, there were 21. 916 cases and 244 deaths, a 66% reduction from the same period in the previous year. In January to December 2015, there were 36. 045 cases (24% increase) and 322 deaths (5% increase).

In 2016 there were a total of 41421 cases and 446 deaths, an increase from the previous year related to rain? There were a sharp decline in 2017 to 13681 cases and 159 deaths. From the beginning of the epidemic to May 2018, the total cumulative cases amounted to 819. 000 and the cumulative death toll to 9769.

An admission of guilt?

Although facing mounting pressure and increasing evidence saying otherwise, the UN publically downplayed its role in the Cholera crisis that is still unresolved in Haiti. Initially the organization denied any wrong-doing. It published its own report about the epidemic, which concluded that ”the introduction of this cholera strain as a result of environmental contamination with feces could not have been the source” and ”the Haiti cholera outbreak was caused by the confluence of circumstances as described, and was not the fault of, or deliberate action of, a group or individual”. Furthermore the report states that the actual origin is no longer relevant in the context of controlling the outbreak.

However, after more than 5 years of denying any responsibility or involvement, in August of 2016 the UN secretary-general Ban Ki-moon publically apologized for the UN´s role in the epidemic. Although not admitting any legal responsibility for the epidemic, the UN announced a 400 million dollar fund aimed at relief for affected Haitians. As of April of 2018, the UN has been criticized for its efforts. The previously mentioned fund had only managed to raise a staggering 8. 7 million dollars, equal to 2. 2% of the projected 400 million. Also, apparently only half of this amount has found its way to its intended recipients. The UN has in later years been taken to court by both affected Haitians and NGO´s in an effort to receive compensation for the victims, but the organization has claimed immunity. Although this has been criticized as exhibiting an untouchable attitude, their claims for immunity has been upheld in U. S. courts. Interestingly, this is not the first case of UN claiming immunity. A similar situation occurred involving lead-poisoning of Roma people in Kosovo displaced by the war in the region, where exposure occurred over several years in temporal UN-refugee camps. No financial compensation or a real apology was issued.

The WHO has resources in place to respond quickly to suspected cases, to monitor and prevent new cases. From January to June of 2018 they provided rapid response to 4, 408 cases, equal to 86% of all suspected cholera cases and 94% being within 48 hours. In the same time period they provided vaccination to nearly 600, 000 people and water treatment products to approximately 60, 000 households. In order to continue the decline in incidence of Cholera in Haiti, adequate sanitation, access to clean drinking water and preventive sensitization in high-risk areas are essential. As an example, two dose vaccination regimen with killed, bivalent, whole-cell oral Cholera provided a 4-year 76% protection according to a case-control study in Haiti. On February of 2013, the Haitian government announced its own national plan for the eradication of cholera within the period of 2013-2022. While complete eradication is yet to be accomplished, it may soon be within reach as new cases has fallen from 170, 000 in the last months of 2010 to 2, 842 cases as of August 2018. A study by Renaud Piarroux et al stated that “Our epidemiologic study provides several additional arguments confirming an importation of cholera in Haiti. There was an exact correlation in time and places between the arrival of a Nepalese battalion from an area experiencing a cholera outbreak and the appearance of the first cases in Meille a few days after. The remoteness of Meille in central Haiti and the absence of report of other incomers make it unlikely that a cholera strain might have been brought there another way. DNA fingerprinting of V. cholerae isolates in Haiti and genotyping corroborate our findings because the fingerprinting and genotyping suggest an introduction from a distant source in a single event”.