What is Vibrio cholerae Infection?
Toxigenic strains of Vibrio cholerae, a specific type of bacteria, are a common cause of severe, dehydrating diarrhea in countries which have poor hygiene conditions, those of low to middle incomes, and also places affected by natural disasters or humanitarian crises. Vibrio cholerae is a kind of bacteria that triggers severe diarrhea, which can lead to rapid dehydration and a dangerous condition called hypovolemia, where there isn’t enough blood for the heart to pump. Cholera illness progresses fast and can result in high death rates if medical treatment is delayed. When treated with prompt rehydration and antibiotics, the fatality rate can drop to less than 1% from more than 50% untreated.
The bacteria gets transmitted through contaminated water or food, following the fecal-oral route. Underprivileged living conditions, poor sanitation, and unsafe water and food are leading risk factors for getting the infection.
Actual instances of cholera often go unreported due to limited surveillance and resources. The World Health Organization (WHO) predicts that each year, between 1.4 to 4.0 million cases and 21,000 to 143,000 deaths are caused by cholera around the world. Historically, cholera has been widespread in the Asian subcontinent, but has spread to other parts of the world including Latin and Central America, and sub-Saharan Africa.
In the past 200 years, seven large-scale outbreaks, or pandemics, of cholera have occurred; the latest began in 1961 and is still ongoing today. The bacteria is also constantly changing, developing new types likely due to exposure to antibiotics.
Cholera continues to be a major public health threat for several reasons: it’s spreading to more regions, outbreaks are unpredictable, it leads to high sickness and death rates, it’s greatly underreported, antibiotic resistance is on the rise, and available resources for treatment are inadequate. The WHO’s Global Task Force for Cholera Control (GTFCC) aims to reduce cholera globally by 90% and eliminate the disease in at least 20 countries by 2030.
Successful cholera treatment includes oral and intravenous rehydration therapy, administration of antibiotics and electrolytes, and oral cholera vaccines, especially in areas where the disease is prevalent or during an outbreak. Good sanitary habits, access to clean water, and sound hygiene practices are also paramount in preventing the transmission of the bacteria.
What Causes Vibrio cholerae Infection?
V cholerae, a bacterium shaped like a comma, is the source of cholera disease. This bacteria is very mobile, moving around with a single whip-like tail, known as a flagellum. It spreads through feces, specifically by contaminated water and food, personal contact with infected people, or through objects touched by those infected. This mode of spreading is especially high in communities affected by natural disasters, wars, or famines, and also can happen within households.
The bacteria live freely and come in many kinds, some harmful and some not. They are classified based on the O antigen in their outer layer. V cholerae is unique as it can tolerate salt and needs it to grow, usually found in coastal waters and salty water contaminated with human or animal waste. This causes occasional infection through shellfish. Bacteria from recently released feces can cause infection for up to 24 hours but can survive for a longer period outside the gut.
Over 200 variations of V. cholerae have been found, but only the toxic variations cause cholera. Among them, only types O1 and O139 have caused cholera epidemics. Non-toxic strains sometimes cause smaller outbreaks and cases of diarrhea as well as stomach inflammation and blood infections.
Serogroup O1, a type of V. cholerae, has serotypes Inaba and Ogawa, and two subtypes, classical and El Tor, known to cause cholera epidemics. The first six pandemics were likely caused by the classical subtype of serotype O1, and the seventh pandemic that started in 1961 is caused by the O1 El Tor subtype. In 1992, the V cholera serotype O139, also known as Bengal, appeared in the Indian subcontinent, causing a cholera epidemic and spread to other areas in Asia, causing large outbreaks.
Whole genome analyses, or the detailed examination of the bacteria’s entire genetic makeup, have tracked the worldwide spread of this bacteria. It turns out that a single subtype, 7PET, is behind the current pandemic and it has been identified to have originated from the Bay of Bengal. The bacteria spread with human travel, causing local and long-lasting regional outbreaks.
The genome of V. cholerae contains two chromosomes which is unique among bacteria. This bacteria evolves rapidly by adding mobile genetic elements to itself. Notable features of the genome include the bacteriophage CTXΦ, a virus that infects bacteria and inserts its genetic material into the bacteria’s genome, and the Vibrio pathogenicity island which produces the toxin that lets the bacteria colonize the intestines.
Risk Factors and Frequency for Vibrio cholerae Infection
The true global impact of cholera is hard to measure because many cases are not diagnosed or reported. Limited resources for diagnosing and monitoring the disease, along with poor healthcare access in many parts of the world, means many cases go unnoticed. Every year, the World Health Organization estimates that between 1.4 to 4.0 million cases of cholera occur, leading to between 21,000 to 143,000 deaths worldwide.
Traditionally, cholera has been a common disease in Asia, but it has spread to other parts of the world. It is now also common in Latin and Central America and sub-Saharan Africa. Over the past two centuries, there have been seven cholera pandemics, with the seventh one still ongoing. This seventh pandemic began in 1961 in Sulawesi, an Indonesian island. It then spread to Africa in 1971 and to the Americas in 1991. The cholera bacteria is continuously evolving, leading to new variants of the bacteria due to the use of antibiotics.
- The bacterium V cholerae caused the first six pandemics. These were likely caused by the ‘classical biotype’ from the O1 group of the bacteria.
- The ongoing seventh pandemic has been caused by the ‘El Tor biotype’, also from the O1 group.
- In 1992, the O139 ‘Bengal’ variant of V cholerae appeared in India. This has since spread throughout Asia, causing widespread outbreaks.
Scientists have been using whole-genome sequencing to study the evolution of V cholerae. This has revealed that a single strain, known as 7PET, is responsible for the current pandemic. This strain is notable for its increased ability to survive in various environments, its heightened resistance to antibiotics, and its increased virulence, or harm-causing potential.
This research has traced cholera’s origins to the Bay of Bengal, which has been the source of six pandemics from 1827 to 1923. The ongoing seventh pandemic has been around since 1961 and has affected South America and much of the Western Hemisphere since 1991. Recently, it has continued to affect vulnerable communities like those in post-earthquake Haiti (2010), Iraq, and Yemen. Factors such as natural disasters, refugee movements, wars, and conflicts increase the risk of infection and outbreaks. Despite water treatment and sanitation systems largely eliminating cholera in Europe and North America, new V cholerae strains, global travel, and migration pose serious public health threats.
Signs and Symptoms of Vibrio cholerae Infection
Cholera is a disease known for causing profuse and painless diarrhea and vomiting without a fever. The severity of diarrhea differs from person to person. Severe cases can lead to a condition called hypovolemic shock due to substantial loss of body fluids and electrolytes. The disease begins with a diarrhea that may contain fecal matter but later transitions to a watery, foul-smelling mucus known as ‘rice-water stools’. Cholera stands out from other diarrhea-related diseases due to the rapid rate of fluid loss and the high concentration of sodium in the stool.
In extreme cases, referred to as cholera gravis, hypotensive shock can manifest within hours from the onset of initial symptoms. Delay in treatment may lead to death, with mortality rates reportedly reaching 70%. There’s also a version of cholera called ‘cholera sicca’ where the fluid accumulates in the intestine leading to circulatory collapse and death before diarrhea symptoms appear.
Signs of cholera in patients suffering from hypovolemic shock might include less urine output, cold and sweaty skin, decreased skin turgor, sunken eyes, rapid and deep breathing (due to acidosis), fast heart rate, and low blood pressure. Electrolyte imbalances can result in muscle cramping and weakness.
The manifestations of cholera are linked to the level of fluid loss. Here are the symptoms and signs related to different percentages of fluid lost:
- 3% to 5% loss of body weight – excessive thirst
- 5% to 8% loss of body weight – postural hypotension, weakness, fast heart rate, fatigue, dry mucous membranes, dry mouth
- More than 10% loss of body weight – oliguria; weak, thin, or undetectable pulse; sunken eyes (sunken fontanelles in infants); skin resembling that of a washerwoman; extreme sleepiness and coma
Testing for Vibrio cholerae Infection
Cholera is usually diagnosed by observing the symptoms in a patient, especially during an outbreak of diarrheal sickness. This illness stands out from other diarrheal diseases due to specific reasons. Cholera affects how the body absorbs chloride and sodium chloride, which typically result in lower levels of potassium and calcium in the body, a condition known as metabolic acidosis, and severe dehydration with balanced sodium levels. In children, very low blood sugar can happen, which can lead to changes in mental status, seizures, or even coma.
However, there’s no strict need for any specific lab or X-ray results to diagnose and treat cholera patients.
To confirm a cholera diagnosis, doctors can identify the bacteria “V cholerae” in stool samples using a method called polymerase chain reaction and quick tests. Despite this, diagnosis does not rely on these tests because cholera is dangerous and can potentially cause death. Treatment should never be delayed for these tests because a clinical diagnosis (based on the symptoms) is typically enough. The stool culture test remains the best way to detect “V cholerae” and find out what will work best against it. This test takes time and isn’t the best when a quick diagnosis is needed.
Rapid diagnostic tests have become more popular since they’re easier to use, less expensive, and quickly provide results, which can be crucial in managing and preventing epidemics. Most of these tests work like a strip test – a fresh stool sample is applied to the strip, and certain chemicals are added to show a positive or negative result. Given the World Health Organization’s focus on faster, lower-cost, and easy-to-use diagnostic tests, new rapid diagnostic tests are being developed continually.
However, relying too heavily on these tests can be risky, as their results can vary. For instance, in the 2010 earthquake in Haiti, such tests revealed their limitations. While these are useful to respond to an outbreak and monitoring diseases, they’re not the best choice for use as point-of-care tests, which are tests conducted immediately in the patient’s care setting for a quick diagnosis.
Treatment Options for Vibrio cholerae Infection
Oral rehydration therapy, which is the process of taking in water with specific amounts of salt and sugar to prevent or treat dehydration, is the main treatment for cholera, an infection in the digestive system. It has greatly improved patient outcomes worldwide for cholera and other diseases that cause severe diarrhea. When a person becomes dehydrated, they lose a significant amount of fluids, and this can be observed through physical signs such as changes in skin elasticity, heart rate, mental state, and dryness of the mouth and throat.
The amount of fluids lost will dictate the appropriate therapy, and in strong cases of cholera patients can lose an average of 20 mL per kg of body weight per hour. Therefore, rehydration needs to begin swiftly. Treatment starts by assessing the initial fluid loss and choosing the right rehydration method. For severely dehydrated patients who may be in a state of shock, emergency rehydration with intravenous fluids might be needed.
The concept of oral rehydration therapy was first established in the 1960s. The World Health Organization (WHO) now recommends different variations of oral rehydration solutions to treat cholera. These solutions are a mix of water, salts and some form of sugar, and they help to replenish lost fluids and electrolytes. Some patients may need additional care, such as those who are suffering from severe vomiting along with diarrhea. In these cases, oral rehydration therapy may not be enough and intravenous fluids may be necessary. Caregivers should continually assess fluid loss to ensure correct rehydration, and measures such as cholera cots have been developed to measure fluid loss effectively.
One common mistake when treating cholera patients is not properly estimating their fluid needs and not regularly checking on their fluid loss. Other treatments like antimicrobials, which are drugs used to kill or stop the growth of microorganisms, are also useful to manage cholera once the initial fluid deficit has been corrected and vomiting has stopped. These medicines greatly improve patient outcomes by reducing the length of diarrhea, decreasing fluid loss, and reducing the spread of the cholera bacteria. However, cholera bacteria can sometimes resist these drugs, which is why treatment should be based on local resistance patterns.
For infants with cholera, breastfeeding alongside oral rehydration therapy is important. Supplements like zinc and vitamin A are also prescribed to help improve recovery. On the other hand, antiemetic drugs, which are used to prevent vomiting, and antimotility medications, used to slow down the rate of stools, may hinder the effectiveness of rehydration therapy, leading to poorer patient outcomes.
What else can Vibrio cholerae Infection be?
If you have an infection from the V cholerae bacteria, your symptoms might look very similar to those from other illnesses. People with cholera can experience a range of problems, from simple diarrhea to severe, watery diarrhea with vomiting that can lead to shock from loss of bodily fluids within hours. There are many diseases that can initiate symptoms of acute watery diarrhea that appear like cholera, so when a new patient comes in complaining of diarrhea, doctors should keep cholera on their list of possible causes. This is especially important if the patient is in an area where there is a known outbreak or where the disease is common. Doctors must gather a detailed patient history, including any recent travels or potential exposures to disease, to evaluate the risk for cholera.
In places where resources are limited and cholera is widespread, infants and young children often get ill from giardia, rotavirus, and cryptosporidium. Older children and adults, on the other hand, frequently contract infections from Escherichia coli.
Here are some diseases that can cause acute watery diarrhea similar to cholera:
- Enterotoxigenic E coli
- V cholerae O1 or O139
- Campylobacter spp
- Nontyphoidal Salmonella enterica
- Aeromonas spp
- Enteroaggregative E coli
- Norovirus
- Adenovirus
- Rotavirus
And here are some that can cause acute bloody diarrhea:
- Shigella spp
- Campylobacter spp
- Enteroinvasive E coli
- Enterohemorrhagic E coli
- Nontyphoidal S enterica
- E histolytica
- Schistosoma mansoni
What to expect with Vibrio cholerae Infection
Before the development of effective oral rehydration therapy, severe cholera had a mortality rate of more than 50%, and this rate was even higher in pregnant women and children. In the United States and Europe, the average fatality rate for a person who has cholera is estimated to be 1%, a target suggested by the World Health Organization (WHO). There has been a significant decrease in the number of cholera death cases in Africa since 1970, though it still averages between 1.9% and 2.9%.
In 2021 and in 2023, the fatality rate due to cholera was higher than the 1% target set by WHO. However, a considerably lower rate is observed in South America. This lower fatality rate is likely because of the availability of adequate treatment centers and competent medical staff there.
Possible Complications When Diagnosed with Vibrio cholerae Infection
The most dangerous complication of a V cholerae infection can be severe and rapid dehydration. This can happen within hours and can cause a drastic drop in blood volume (hypovolemic shock) and a harmful chemical imbalance in your body (metabolic acidosis). This can be life-threatening. However, with timely and correct treatment, patients usually recover completely without any long-term effects.
Complications of V Cholerae Infection:
- Rapid and severe dehydration
- Hypovolemic shock
- Metabolic acidosis
- Potential fatality
Notably, with the right treatment:
- Full recovery is usual
- No long-term effects are expected
Preventing Vibrio cholerae Infection
Cholera is a disease you can catch if you eat food or drink water that’s been exposed to a bacteria named V cholerae. This bacteria is commonly found in certain parts of the world, which we call endemic areas. People who live in or are traveling to these areas should be very careful about washing their hands thoroughly. It’s also crucial to make sure any water used for drinking or washing food is properly boiled before use. Vaccines are available that can offer some protection against cholera if you’re in these areas.
If someone from these endemic areas starts experiencing symptoms of cholera, they should see a doctor immediately. Keep in mind, the best way to prevent getting sick from cholera is through proper hygiene, improving living environments, and following all the prevention tips from the World Health Organization (WHO). It’s also important to be aware of social dynamics. These are ideas and behaviours that a group of people share and this understanding can help us better target prevention efforts and possibly even stop cholera from spreading.
Areas with cholera outbreaks often share certain social and economic qualities. This shows how the social and economic status of a country can influence the spread of a disease that can actually be prevented. Because of this, more research is being done and collaboration is strengthening between public health workers, government, and medical professionals. Together, they are working to develop drinkable cholera vaccines and to improve how these vaccines are given out and used.
