Typhoid fever salmonella typhi

Key facts

• Typhoid fever is a life-threatening infection caused by the bacterium Salmonella Typhi. It is usually spread through contaminated food or water.
• An estimated 11–20 million people get sick from typhoid and between 128 000 and 161 000 people die from it every year.
• Symptoms include prolonged fever, fatigue, headache, nausea, abdominal pain, and constipation or diarrhoea. Some patients may have a rash. Severe cases may lead to serious complications or even death.
• Typhoid fever can be treated with antibiotics although increasing resistance to different types of antibiotics is making treatment more complicated.
• Two vaccines have been used for many years to prevent typhoid. A new typhoid conjugate vaccine with longer lasting immunity was prequalified by WHO in December 2017.

Typhoid fever is a life-threatening infection caused by the bacterium SalmonellaTyphi. It is usually spread through contaminated food or water. Once SalmonellaTyphi bacteria are eaten or drunk, they multiply and spread into the bloodstream.

Urbanization and climate change have the potential to increase the global burden of typhoid. In addition, increasing resistance to antibiotic treatment is making it easier for typhoid to spread through overcrowded populations in cities and inadequate and/or flooded water and sanitation systems.

Symptoms

Salmonella Typhi lives only in humans. Persons with typhoid fever carry the bacteria in their bloodstream and intestinal tract. Symptoms include prolonged high fever, fatigue, headache, nausea, abdominal pain, and constipation or diarrhoea. Some patients may have a rash. Severe cases may lead to serious complications or even death. Typhoid fever can be confirmed through blood testing.

Epidemiology, risk factors, and disease burden

Improved living conditions and the introduction of antibiotics resulted in a drastic reduction of typhoid fever morbidity and mortality in industrialized countries. In developing areas of Africa, the Americas, South-East Asia and the Western Pacific regions, however, the disease continues to be a public health problem.

WHO estimates the global typhoid fever disease burden at 11-20 million cases annually, resulting in about 128 000–161 000 deaths per year.

Typhoid risk is higher in populations that lack access to safe water and adequate sanitation. Poor communities and vulnerable groups including children are at highest risk.

Treatment

Typhoid fever can be treated with antibiotics. As resistance to antibiotics has emerged including to fluoroquinolones, newer antibiotics such as cephalosporins and azithromycin are used in the affected regions. Resistance to azithromycin has been reported sporadically but it is not common as of yet.

Even when the symptoms go away, people may still be carrying typhoid bacteria, meaning they can spread it to others through their faeces.

It is important for people being treated for typhoid fever to do the following:

• Take prescribed antibiotics for as long as the doctor has prescribed.
• Wash their hands with soap and water after using the bathroom, and do not prepare or serve food for other people. This will lower the chance of passing the infection on to someone else.
• Have their doctor test to ensure that no Salmonella Typhi bacteria remain in their body.

Prevention

Typhoid fever is common in places with poor sanitation and a lack of safe drinking water. Access to safe water and adequate sanitation, hygiene among food handlers and typhoid vaccination are all effective in preventing typhoid fever.

Two vaccines have been used for many years to protect people from typhoid fever:

• an injectable vaccine based on the purified antigen for people aged over 2 years
• a live attenuated oral vaccine in capsule formulation for people aged over 5 years

These vaccines do not provide long-lasting immunity and are not approved for children younger than 2 years old.

A new typhoid conjugate vaccine, with longer lasting immunity, was prequalified by WHO in December 2017 for use in children from the age of 6 months.

All travelers to endemic areas are at potential risk of typhoid fever, although the risk is generally low in tourist and business centres where standards of accommodation, sanitation and food hygiene are high. Typhoid fever vaccination should be offered to travelers to destinations where the risk of typhoid fever is high.

The following recommendations will help ensure safety while travelling:

• Ensure food is properly cooked and still hot when served.
• Avoid raw milk and products made from raw milk. Drink only pasteurized or boiled milk.
• Avoid ice unless it is made from safe water.
• When the safety of drinking water is questionable, boil it or if this is not possible, disinfect it with a reliable, slow-release disinfectant agent (usually available at pharmacies).
• Wash hands thoroughly and frequently using soap, in particular after contact with pets or farm animals, or after having been to the toilet.
• Wash fruits and vegetables carefully, particularly if they are eaten raw. If possible, vegetables and fruits should be peeled.

WHO response

In December 2017, WHO prequalified the first conjugate vaccine for typhoid. This new vaccine has longer-lasting immunity than older vaccines, requires fewer doses and can be given to children from the age of 6 months.

This vaccine will be prioritized for countries with the highest burden of typhoid disease. This will help reduce the frequent use of antibiotics for typhoid treatment, which will slow the increase in antibiotic resistance in Salmonella Typhi.

In October 2017, the Strategic Advisory Group of Experts (SAGE) on immunization, which advises WHO, recommended typhoid conjugate vaccines for routine use in children over 6 months of age in typhoid endemic countries. SAGE also called for the introduction of typhoid conjugate vaccines to be prioritized for countries with the highest burden of typhoid disease or of antibiotic resistance to Salmonella Typhi.

Shortly after SAGE’s recommendation, the Gavi Board approved US$ 85 million in funding for typhoid conjugate vaccines starting in 2019.

What is typhoid fever?

Typhoid fever is an acute illness associated with fever caused by the Salmonella enterica serotype Typhi bacteria. It can also be caused by Salmonella paratyphi, a related bacterium that usually causes a less severe illness. The bacteria are deposited in water or food by a human carrier and are then spread to other people in the area.

The incidence of typhoid fever in the United States has markedly decreased since the early 1900s, when tens of thousands of cases were reported in the U.S. Today, less than 400 cases are reported annually in the United States, mostly in people who have recently traveled to Mexico and South America. This improvement is the result of better environmental sanitation. India, Pakistan, and Egypt are also known as high-risk areas for developing this disease. Worldwide, typhoid fever affects more than 21 million people annually, with about 200,000 people dying from the disease.

How Do People Get Typhoid Fever?

Typhoid fever is contracted by drinking or eating the bacteria in contaminated food or water. People with acute illness can contaminate the surrounding water supply through stool, which contains a high concentration of the bacteria. Contamination of the water supply can, in turn, taint the food supply. The bacteria can survive for weeks in water or dried sewage.

About 3%-5% of people become carriers of the bacteria after the acute illness. Others suffer a very mild illness that goes unrecognized. These people may become long-term carriers of the bacteria -- even though they have no symptoms -- and be the source of new outbreaks of typhoid fever for many years.

How Is Typhoid Fever Diagnosed?

After the ingestion of contaminated food or water, the Salmonella bacteria invade the small intestine and enter the bloodstream temporarily. The bacteria are carried by white blood cells in the liver, spleen, and bone marrow, where they multiply and reenter the bloodstream. People develop symptoms, including fever, at this point. Bacteria invade the gallbladder, biliary system, and the lymphatic tissue of the bowel. Here, they multiply in high numbers. The bacteria pass into the intestinal tract and can be identified in stool samples. If a test result isn't clear, blood or urine samples will be taken to make a diagnosis.

What Are the Symptoms of Typhoid Fever?

The incubation period is usually 1-2 weeks, and the duration of the illness is about 3-4 weeks. Symptoms include:

• Poor appetite
• Headaches
• Generalized aches and pains
• Fever as high as 104 degrees Farenheit
• Lethargy
• Diarrhea

Chest congestion develops in many people, and abdominal pain and discomfort are common. The fever becomes constant. Improvement occurs in the third and fourth week in those without complications. About 10% of people have recurrent symptoms after feeling better for one to two weeks. Relapses are actually more common in individuals treated with antibiotics.

How Is Typhoid Fever Treated?

Typhoid fever is treated with antibiotics which kill the Salmonella bacteria. Prior to the use of antibiotics, the fatality rate was 20%. Death occurred from overwhelming infection, pneumonia, intestinal bleeding, or intestinal perforation. With antibiotics and supportive care, mortality has been reduced to 1%-2%. With appropriate antibiotic therapy, there is usually improvement within one to two days and recovery within seven to 10 days.

Several antibiotics are effective for the treatment of typhoid fever. Chloramphenicol was the original drug of choice for many years. Because of rare serious side effects, chloramphenicol has been replaced by other effective antibiotics. The choice of antibiotics is guided by identifying the geographic region where the infection was contracted (certain strains from South America show a significant resistance to some antibiotics.) If relapses occur, patients are retreated with antibiotics.

Those who become chronically ill (about 3%-5% of those infected), can be treated with prolonged antibiotics. Often, removal of the gallbladder, the site of chronic infection, will provide a cure.

For those traveling to high-risk areas, vaccines are now available.

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Background

Typhoid fever, also known as enteric fever, is a potentially fatal multisystemic illness caused primarily by Salmonella enterica serotype typhi and, to a lesser extent, S enterica serotypes paratyphi A, B, and C. The terms typhoid and enteric fever are commonly used to describe both major serotypes.

Typhoid fever has a wide variety of presentations that range from an overwhelming multisystemic illness to relatively minor cases of diarrhea with low-grade fever. The classic presentation is fever, malaise, diffuse abdominal pain, and constipation. Untreated typhoid fever may progress to delirium, obtundation, intestinal hemorrhage, bowel perforation, and death within 1 month of onset. Survivors may be left with long-term or permanent neuropsychiatric complications.

S typhi has been a major human pathogen for thousands of years, thriving in conditions of poor sanitation, crowding, and social chaos. It may have responsible for the Great Plague of Athens at the end of the Pelopennesian War. [1] The name S typhi is derived from the ancient Greek typhos, an ethereal smoke or cloud that was believed to cause disease and madness. In the advanced stages of typhoid fever, the patient's level of consciousness is truly clouded. Although antibiotics have markedly reduced the frequency of typhoid fever in the developed world, it remains endemic in developing countries. [2] Infections with S paratyphi may be surpassing those caused by S typhi, in part because of immunological naivete among the population and incomplete coverage by vaccines that target typhi.

Note that some writers refer to the typhoid and paratyphoid fever as distinct syndromes caused by the typhi versus paratyphi serovars, while others use the term typhoid fever for a disease caused by either one. We use the latter terminology. We refer to these serovars collectively as typhoidal salmonella.

Pathophysiology

All pathogenic Salmonella species, when present in the gut are engulfed by phagocytic cells, which then pass them through the mucosa and present them to the macrophages in the lamina propria. Nontyphoidal salmonellae are phagocytized throughout the distal ileum and colon. With toll-like receptor (TLR)–5 and TLR-4/MD2/CD-14 complex, macrophages recognize pathogen-associated molecular patterns (PAMPs) such as flagella and lipopolysaccharides. Macrophages and intestinal epithelial cells then attract T cells and neutrophils with interleukin 8 (IL-8), causing inflammation and suppressing the infection. [3, 4]

In contrast to the nontyphoidal salmonellae, S typhi and paratyphi enter the host's system primarily through the distal ileum. They have specialized fimbriae that adhere to the epithelium over clusters of lymphoid tissue in the ileum (Peyer patches), the main relay point for macrophages traveling from the gut into the lymphatic system. The bacteria then induce their host macrophages to attract more macrophages. [3]

S typhi has a Vi capsular antigen that masks PAMPs, avoiding neutrophil-based inflammation, while the most common paratyphi serovar, paratyphi A, does not. This may explain the greater infectivity of typhi compared with most of its cousins. [5]

Typhoidal salmonella co-opt the macrophages' cellular machinery for their own reproduction [6] as they are carried through the mesenteric lymph nodes to the thoracic duct and the lymphatics and then through to the reticuloendothelial tissues of the liver, spleen, bone marrow, and lymph nodes. Once there, they pause and continue to multiply until some critical density is reached. Afterward, the bacteria induce macrophage apoptosis, breaking out into the bloodstream to invade the rest of the body. [4]

The bacteria then infect the gallbladder via either bacteremia or direct extension of infected bile. The result is that the organism re-enters the gastrointestinal tract in the bile and reinfects Peyer patches. Bacteria that do not reinfect the host are typically shed in the stool and are then available to infect other hosts. [2, 4] See the image below.

Chronic carriers are responsible for much of the transmission of the organism. While asymptomatic, they may continue to shed bacteria in their stool for decades. The organisms sequester themselves either as a biofilm on gallstones or gallbladder epithelium or, perhaps, intracellularly, within the epithelium itself. [7] The bacteria excreted by a single carrier may have multiple genotypes, making it difficult to trace an outbreak to its origin. [8]

Typhoidal salmonella have no nonhuman vectors. An inoculum as small as 100,000 organisms of typhi causes infection in more than 50% of healthy volunteers. [9] Paratyphi requires a much higher inoculum to infect, and it is less endemic in rural areas. Hence, the patterns of transmission are slightly different.

The following are modes of transmission of typhoidal salmonella:

Oral transmission via food or beverages handled by an often asymptomatic individual—a carrier—who chronically sheds the bacteria through stool or, less commonly, urine

Hand-to-mouth transmission after using a contaminated toilet and neglecting hand hygiene

Oral transmission via sewage-contaminated water or shellfish (especially in the developing world). [10, 11, 12]

Paratyphi is more commonly transmitted in food from street vendors. It is believed that some such foods provide a friendly environment for the microbe.

Paratyphi is more common among newcomers to urban areas, probably because they tend to be immunologically naïve to it. Also, travellers get little or no protection against paratyphi from the current typhoid vaccines, all of which target typhi. [13, 14]

Typhoidal salmonella are able to survive a stomach pH as low as 1.5. Antacids, histamine-2 receptor antagonists (H2 blockers), proton pump inhibitors, gastrectomy, and achlorhydria decrease stomach acidity and facilitate S typhi infection. [4]

HIV/AIDS is clearly associated with an increased risk of nontyphoidal Salmonella infection; however, the data and opinions in the literature as to whether this is true for S typhi or paratyphi infection are conflicting. If an association exists, it is probably minor. [15, 16, 17, 18]

Other risk factors for typhoid fever include various genetic polymorphisms. These risk factors often also predispose to other intracellular pathogens. For instance, PARK2 and PACGR code for a protein aggregate that is essential for breaking down the bacterial signaling molecules that dampen the macrophage response. Polymorphisms in their shared regulatory region are found disproportionately in persons infected with Mycobacterium leprae and S typhi. [11]

On the other hand, protective host mutations also exist. The fimbriae of S typhi bind in vitro to cystic fibrosis transmembrane conductance receptor (CFTR), which is expressed on the gut membrane. Two to 5% of white persons are heterozygous for the CFTR mutation F508del, which is associated with a decreased susceptibility to typhoid fever, as well as to cholera and tuberculosis. The homozygous F508del mutation in CFTR is associated with cystic fibrosis. Thus, typhoid fever may contribute to evolutionary pressure that maintains a steady occurrence of cystic fibrosis, just as malaria maintains sickle cell disease in Africa. [19, 20]

As the middle class in south Asia grows, some hospitals there are seeing a large number of typhoid fever cases among relatively well-off university students who live in group households with poor hygiene. [21] American clinicians should keep this in mind, as students from these areas often come to the United States for further education. [22]

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.

StatPearls [Internet].

John V. Ashurst ; Justina Truong ; Blair Woodbury .

Last Update: November 14, 2019 .

Introduction

Salmonella enterica serotype typhi is a gram-negative bacterium that is responsible for typhoid fever and has been a burden on developing nations for generations. In 1829, Pierre Louis was the first to coin the term “typhoid fever” after identifying lesions in the abdominal lymph nodes of patients who had died from “gastric fever.” [1] The term was derived from the Greek word “typhus” which meant “smoky” and was used to describe the delirium that patients would exhibit with the disease. [1] Although first described in the early 1800s, it was not until 1880 when the organism for typhoid fever was discovered. [1] In 1880, German pathologist Karl Eberth identified S. enterica. It was first cultured in 1884 by Georg Gaffky. [1] Several years later, Almroth Wright developed a vaccine for the disease. [1] Despite significant efforts in research and medical advancements, typhoid fever is still a major, worldwide, public health concern.

Etiology

Salmonella enterica serotype typhi is a gram-negative, rod-shaped, flagellated bacterium whose only reservoir is the human body. [2][3] The bacterium is serologically positive for lipopolysaccharide antigens O9 and O12 as well as the distinct polysaccharide capsular antigen Vi. [2][3] Antigen Vi-negative strains appear to be less infectious and less virulent as compared to those strains that are Vi positive. [2]

Epidemiology

Typhoid fever is more common in children and young adults and is associated with low-income areas in which poor sanitation is prevalent. [2][3][4] In 2000, typhoid fever was estimated to cause 21.7 million illnesses and 216,000 deaths globally, and the International Vaccine Institute estimated that there were 11.9 million cases of typhoid fever and 129,000 deaths in low to middle-income countries in 2010. [5][6] However, these numbers are more than likely an under-representation of the true disease burden given a large proportion of patients are treated on an outpatient basis or receive no treatment at all. In the United States, approximately 200 to 300 cases of Salmonella enterica serotype typhi are reported each year, and approximately 80% of these cases are from travelers returning from an endemic region. [7][8]

In the pre-antibiotic era, mortality rates were 15% or greater. However, mortality rates have fallen to less than 1% with the introduction of antibiotics. [3][9]

Pathophysiology

Salmonella enterica serotype typhi is usually contracted by ingestion of food or water that is contaminated with the excrements of those that carry the organism and must survive the gastric pH barrier in the stomach prior to adherence in the small intestine. [3] An infectious dose of Salmonella enterica serotype typhi in healthy individuals ranges between 1000 and 1 million organisms but can be related to the host’s defense mechanisms. [3]

Salmonella enterica serotype typhi enter the submucosal region of the small bowel by either direct penetration into the epithelial tissue mediated by the cystic fibrosis transmembrane conductance regulator (CFTR) or via the M-cell, a specialized lymphoid epithelial cell. Once within the submucosa, the bacterium causes hypertrophy of the Peyer’s patches. [3][2][10]

Dissemination of the organism from the Peyer’s patches occurs via the lymphatic system and the bloodstream. [2][3] Cellular replication within the reticuloendothelial system is a hallmark of the disease and eventually causes the systemic symptoms that a clinician will observe.[2] Following replication, organisms will reside in the macrophages of the liver, spleen and bone marrow. [2] Classically, Salmonella enterica serotype typhi can be cultured from the bone marrow even after anti-microbial therapy has been initiated. [2]

Approximately 1% to 5% of patients will become chronic carriers of Salmonella enterica serotype typhi despite adequate antimicrobial therapy. [3] A chronic carrier is defined as a patient that has excretion of the bacterium in the stool or urine for greater than 12 months after an acute infection and is typically is of the female gender or has cholelithiasis. [2][3] Those in the chronic carrier state will typically have high levels of antibodies to the Vi antigen and will not develop the clinical disease. The most famous of these chronic carriers was Mary Mallon who was diagnosed as a “healthy carrier” of the disease in 1906 after transmitting the disease to several households in which she served as the cook. [1] The term “Typhoid Mary” became prominent during public health campaigns and is still used in modern culture today. [1]

History and Physical

Patients will typically present after a 7 to 14-day asymptomatic period after initial inoculation with Salmonella enterica serotype typhi. [2][3] Following the initial asymptomatic period, patients will present with an influenza-like illness with associated fever [2] Abdominal symptoms are always present during the progression of the disease and can include pain, nausea, vomiting, constipation, or diarrhea. [2][3] As the disease progresses, the patient’s may develop intermittent confusion and an apathetic affect. Unlike malaria, there will be little to no diurnal variation in fevers and patients will not experience rigors. [2]

Although classically related to typhoid fever, relative bradycardia in association with a fever is not always seen in patient’s infected with Salmonella enterica serotype typhi and could be related to the geographical area in which the infection occurs. [2] However, the abdominal pain will be seen in all patients and can range from diffuse in nature to pain that mimics appendicitis. [2] Hepatomegaly and splenomegaly will typically develop during a patient’s disease progression. [2] Rose spots, a blanching erythematous maculopapular rash with lesions 2 to 4 mm in diameter, may develop on the chest and abdomen of patients. [2]

Evaluation

The diagnosis of typhoid fever should be suspected in those living in endemic areas or those who have traveled to an endemic area and are presenting with a febrile illness. Basic laboratory data can aid the clinician in the diagnosis, but no single laboratory value is pathognomonic for typhoid fever. A complete blood count may show either leukocytosis or leukopenia with a left shift depending on the patient’s age. [2][3] Also, relative anemia could be present. [2][3] If a complete metabolic profile is obtained, abnormal liver function tests maybe observed. [2][3]

To confirm the diagnosis, the clinician should obtain blood and stool cultures whenever possible. Blood cultures are positive in 40 to 80% of individuals and stool cultures between 30 to 40%. [2][3][11] However, stool cultures become less sensitive as systemic symptoms arise [11]. The most sensitive diagnostic test that a clinician can obtain is a bone marrow aspirate. Although invasive, more than 90% of cultures are positive in those infected with Salmonella enterica serotype typhi and can stay positive for days after initiation of antimicrobial therapy [2][3]

The Widal test measures agglutinating antibodies against the lipopolysaccharide O and flagellar H antigens. Ideally, a positive test requires a four-fold increase in antibody titers taken 10 days apart, but many clinicians use a single acute-phase sample to guide care. Using this method, false-negative and positive results may occur.

Treatment / Management

The first antibiotic to be used to treat infections caused by Salmonella enterica serotype typhi was chloramphenicol. [3] Only 2 years later, resistant forms of Salmonella enterica serotype typhi were discovered in the community. [3] Currently, ciprofloxacin or ofloxacin have become the mainstay of treatment. [2][3][12] Despite the risks associated with quinolone therapy in children, they are acceptable to use for severe infection or when alternative therapies are unavailable. [2][3] When resistance to a quinolone is identified, an extended spectrum cephalosporin such as ceftriaxone can be used. Another option for those infected with a quinolone resistant strain of Salmonella enterica serotype typhi would be azithromycin. [2][3] Combination therapy of the fluoroquinolones, cephalosporins and macrolides have been used in those who fail to respond to standard therapies. [2][3]

Differential Diagnosis

The differential diagnosis of those infected with Salmonella enterica serotype typhi should include:

Typhoid is a bacterial infection that can lead to a high fever, diarrhea, and vomiting. It can be fatal. It is caused by the bacteria Salmonella typhi.

The infection is often passed on through contaminated food and drinking water, and it is more prevalent in places where handwashing is less frequent. It can also be passed on by carriers who do not know they carry the bacteria.

Annually, there are around 5,700 cases in the United States, and 75 percent of these start while traveling internationally. Globally, around 21.5 million people a year contract typhoid.

If typhoid is caught early, it can be successfully treated with antibiotics; if it is not treated, typhoid can be fatal.

• Typhoid is a common bacterial infection in countries with low incomes.
• Untreated, it is fatal in around 25 percent of cases.
• Symptoms include a high fever and gastrointestinal problems.
• Some people carry the bacteria without developing symptoms
• Most cases reported in the United States are contracted overseas
• The only treatment for typhoid is antibiotics

Share on Pinterest Typhoid is an infection caused by Salmonella typhimurium bacteria that is spread from human to human.

Typhoid is an infection caused by the bacterium Salmonella typhimurium (S. typhi).

The bacterium lives in the intestines and bloodstream of humans. It spreads between individuals by direct contact with the feces of an infected person.

No animals carry this disease, so transmission is always human to human.

If untreated, around 1 in 5 cases of typhoid can be fatal. With treatment, fewer than 4 in 100 cases are fatal.

S. typhi enters through the mouth and spends 1 to 3 weeks in the intestine. After this, it makes its way through the intestinal wall and into the bloodstream.

From the bloodstream, it spreads into other tissues and organs. The immune system of the host can do little to fight back because S. typhi can live within the host’s cells, safe from the immune system.

Typhoid is diagnosed by detecting the presence of S. typhi via blood, stool, urine, or bone marrow sample.

Symptoms normally begin between 6 and 30 days after exposure to the bacteria.

The two major symptoms of typhoid are fever and rash. Typhoid fever is particularly high, gradually increasing over several days up to 104 degrees Fahrenheit, or 39 to 40 degrees Celsius.

The rash, which does not affect every patient, consists of rose-colored spots, particularly on the neck and abdomen.

Other symptoms can include:

Rarely, symptoms might include confusion, diarrhea, and vomiting, but this is not normally severe.

In serious, untreated cases, the bowel can become perforated. This can lead to peritonitis, an infection of the tissue that lines the inside of the abdomen, which has been reported as fatal in between 5 and 62 percent of cases.

Another infection, paratyphoid, is caused by Salmonella enterica. It has similar symptoms to typhoid, but it is less likely to be fatal.

The only effective treatment for typhoid is antibiotics. The most commonly used are ciprofloxacin (for non-pregnant adults) and ceftriaxone.

Other than antibiotics, it is important to rehydrate by drinking adequate water.

In more severe cases, where the bowel has become perforated, surgery may be required.

As with a number of other bacterial diseases, there is currently concern about the growing resistance of antibiotics to S. typhi.

This is impacting the choice of drugs available to treat typhoid. In recent years, for example, typhoid has become resistant to trimethoprim-sulfamethoxazole and ampicillin.

Ciprofloxacin, one of the key medications for typhoid, is also experiencing similar difficulties. Some studies have found Salmonella typhimurium resistance rates to be around 35 percent.

Typhoid is caused by the bacteria S. typhi and spread through food, drinks, and drinking water that are contaminated with infected fecal matter. Washing fruit and vegetables can spread it, if contaminated water is used.

Some people are asymptomatic carriers of typhoid, meaning that they harbor the bacteria but suffer no ill effects. Others continue to harbor the bacteria after their symptoms have gone. Sometimes, the disease can appear again.

People who test positive as carriers may not be allowed to work with children or older people until medical tests show that they are clear.

Countries with less access to clean water and washing facilities typically have a higher number of typhoid cases.

Before traveling to a high-risk area, getting vaccinated against typhoid fever is recommended.

This can be achieved by oral medication or a one-off injection:

• Oral: a live, attenuated vaccine. Consists of 4 tablets, one to be taken every second day, the last of which is taken 1 week before travel.
• Shot, an inactivated vaccine, administered 2 weeks before travel.

Vaccines are not 100 percent effective and caution should still be exercised when eating and drinking.

Vaccination should not be started if the individual is currently ill or if they are under 6 years of age. Anyone with HIV should not take the live, oral dose.

The vaccine may have adverse effects. One in 100 people will experience a fever. After the oral vaccine, there may be gastrointestinal problems, nausea, and headache. However, severe side effects are rare with either vaccine.

There are two types of typhoid vaccine available, but a more powerful vaccine is still needed. The live, oral version of the vaccine is the strongest of the two. After 3 years, it still protects individuals from infection 73 percent of the time. However, this vaccine has more side effects.

The current vaccines are not always effective, and because typhoid is so prevalent in poorer countries, more research needs to be done to find better ways of preventing its spread.

Even when the symptoms of typhoid have passed, it is still possible to be carrying the bacteria.

This makes it hard to stamp out the disease, because carriers whose symptoms have finished may be less careful when washing food or interacting with others.

People traveling in Africa, South America, and Asia, and India in particular, should be vigilant.

Typhoid is spread by contact and ingestion of infected human feces. This can happen through an infected water source or when handling food.

The following are some general rules to follow when traveling to help minimize the chance of typhoid infection:

• Drink bottled water, preferably carbonated.
• If bottled water cannot be sourced, ensure water is heated on a rolling boil for at least one minute before consuming.
• Be wary of eating anything that has been handled by someone else.
• Avoid eating at street food stands, and only eat food that is still hot.
• Do not have ice in drinks.
• Avoid raw fruit and vegetables, peel fruit yourself, and do not eat the peel.