Typhoid fever is caused by Salmonella typhi bacteria. Typhoid fever is rare in industrialized countries. However, it remains a serious health threat in the developing world, especially for children.
Typhoid fever spreads through contaminated food and water or through close contact with someone who’s infected. Signs and symptoms usually include high fever, headache, abdominal pain, and either constipation or diarrhea.
Most people with typhoid fever feel better within a few days of starting antibiotic treatment, although a small number of them may die of complications. Vaccines against typhoid fever are available, but they’re only partially effective. Vaccines usually are reserved for those who may be exposed to the disease or are traveling to areas where typhoid fever is common.
How is typhoid fever spread?
Salmonella Typhi lives only in humans. Persons with typhoid fever carry the bacteria in their bloodstream and intestinal tract. In addition, a small number of persons, called carriers, recover from typhoid fever but continue to carry the bacteria. Both ill persons and carriers shed Salmonella Typhi in their feces (stool).
You can get typhoid fever if you eat food or drink beverages that have been handled by a person who is shedding Salmonella Typhi or if sewage contaminated with Salmonella Typhi bacteria gets into the water you use for drinking or washing food. Therefore, typhoid fever is more common in areas of the world where handwashing is less frequent and water is likely to be contaminated with sewage.
Once Salmonella Typhi bacteria are eaten or drunk, they multiply and spread into the bloodstream. The body reacts with fever and other signs and symptoms.
Types
Typhoid fever
Is caused by a Gram-negative organism Salmonella enterica subspecies enterica serovar Typhi (Salmonella typhi).
Paratyphoid fever
Is divided into three subtypes (A, B and C). Paratyphoid fever is caused by any of three serovars of Salmonella enterica subspecies enterica:
paratyphi A.
schottmuelleri (also called S. paratyphi B).
hirschfeldii (also called S. paratyphi C).
Type A is the most common worldwide, although B predominates in Europe. Type C is rare, and is seen only in the Far East.
The overall ratio of disease caused by S. typhi to that caused by S. paratyphi is about 10 to 1.
Risk factors
Typhoid fever remains a serious worldwide threat especially in the developing world affecting an estimated 26 million or more people each year. The disease is endemic in India, Southeast Asia, Africa, South America and many other areas.
Worldwide, children are at greatest risk of getting the disease, although they generally have milder symptoms than adults do.
If you live in a country where typhoid fever is rare, you’re at increased risk if you:
Work in or travel to areas where typhoid fever is endemic
Work as a clinical microbiologist handling Salmonella typhi bacteria
Have close contact with someone who is infected or has recently been infected with typhoid fever
Drinking water contaminated by sewage that contains typhi
Causes
Typhoid fever is caused by infection with Salmonella typhi. Salmonella typhi is similar to, but not the same as, the Salmonella bacteria that causes food poisoning in the US. Unlike most types of Salmonella, Salmonella typhi only live and reproduce inside humans.
Route of Transmission
Salmonella typhi is transmitted via the fecal-oral route. This means that it is spread from person to person when you eat, drink or even touch your mouth with anything contaminated with infected feces. Because the Salmonella typhi multiply in human intestines, the bacteria is shed in the feces (solid material passed during a bowel movement).
Modes of Transmission
Anything that becomes contaminated with feces that contain Salmonella typhi has the potential to spread the virus. The following are several ways you can get yellow fever:
Drinking contaminated water
Eating fresh fruits or vegetables that have been washed with contaminated water
Eating food prepared by someone who has not washed their hands thoroughly
Touching your mouth after going to the bathroom, before you wash your hands
Eating seafood harvested from a contaminated body of water (lake, ocean, river)
Having oral or anal sex with someone who is infected with the bacteria
High-risk Destinations
Typhoid fever is most common in countries where there is poor sanitation and lack of access to clean drinking water. In these countries it is more likely that infected human feces contaminate the water supply. In addition, handwashing may not be practiced as frequently as in developed countries (where food establishments require employees to wash hands).
Carriers
In some people the bacteria survives in the body even after treatment has effectively relieved their symptoms. These people are considered carriers, because the bacteria continues to be shed through their feces, so contact with their feces carries the disease to other people. Carriers don’t realize they are still infected because they don’t have symptoms.
Symptoms
Symptoms usually appear 1 or 2 weeks after infection but may take as long as 3 weeks to appear. Typhoid usually causes a high, sustained fever, often as high as 40°C (104°F), and extreme exhaustion.
Other common symptoms include:
Constipation
Cough
Headache
Loss of appetite
Stomach pains
Sore throat
Rarer symptoms include:
Bleeding from the rectum
Delirium
Diarrhea
Temporary pink spots on the chest and abdomen
In some people, signs and symptoms may return up to two weeks after the fever has subsided.
Complications
Serious complications of typhoid fever usually occur only in people who have not been treated or are treated late in the illness. Complications tend to develop during the third week of infection. The two most serious complications of typhoid fever are intestinal bleeding and intestinal perforation.
Intestinal Bleeding
Without treatment the bacteria continue to multiply in the intestines. Intestinal bleeding as a potential complication. The seriousness of the complication depends on the severity of the bleeding– how much blood is lost and how quickly. The first sign of intestinal bleeding can be a sudden drop in blood pressure. The following are symptoms of intestinal bleeding:
Fatigue
Shortness of breath
Pale skin
Irregular heartbeat
Vomiting blood
Blood in stools (stools appear dark and tar-like)
Intestinal bleeding may require a blood transfusion to replace blood loss.
Intestinal Perforation
Intestinal perforation is always a life-threatening complication. A perforation occurs when a hole develops in the walls of the intestines. The contents of the intestines then leak out through the hole and collect in the abdominal cavity. Perforation essentially lets the bacteria loose inside the body. The peritoneum is the lining of the abdominal cavity. Intestinal perforation can cause inflammation or infection of the peritoneum, a condition known as peritonitis. The following are signs and symptoms of intestinal perforation:
Severe abdominal pain
Nausea
Vomiting
Sepsis (infection in the bloodstream)
Intestinal perforation is a medical emergency and requires immediate medical attention.
Diagnosis and test
Diagnosis includes questions about travel, examining blood, stool or bone marrow for evidence of infection, and additional testing to determine the particular strain of Salmonella typhi that is causing the illness.
Travel Abroad
Once symptoms have been evaluated, if typhoid fever (or any other unusual infectious disease) is suspected, your doctor will ask detailed questions about travel and potential contact with someone who has traveled or may be carrying the bacteria, such as the following:
Have you traveled out of the country recently?
What country did you travel to?
Do you remember what you ate or drank while you were there?
Do you have a family member or partner who has traveled abroad recently? Where did they travel?
Blood or stool sample
A sample of your blood and/or feces will be sent to the lab to be cultured to see if the S. typhi bacteria grow (the test is called a blood culture or stool culture). In some cases an antibody test might be used to look for substances associated with Typhoid bacteria. A complete blood count (CBC) measures the number and type of blood cells in your blood sample. If you have typhoid fever the CBC may reveal a high white blood cell (WBC) count and a low number of platelets (blood cell fragments that help with blood clotting). If your tests are positive your close contacts and family members may also be tested for the illness.
Bone marrow biopsy
A bone marrow biopsy is a more accurate method of diagnosing typhoid fever, but it is much more complicated to perform. The bone marrow is the spongy material in the middle of certain bones that produce blood cells. A bone marrow biopsy involves using a long, hollow needle inserted into a bone, usually the pelvis or the breast bone, to obtain a tissue sample, which is examined under a microscope for evidence of the infection. A bone marrow biopsy is only performed if other tests are inconclusive.
Strain identification
Further testing can determine what antibiotics will be most effective against your particular strain of Salmonella typhi.
Treatment and medications
Antibiotic therapy is the only effective treatment for typhoid fever.
Commonly prescribed antibiotics
Ciprofloxacin (Cipro): In the United States, doctors often prescribe this for nonpregnant adults.
Ceftriaxone (Rocephin): This injectable antibiotic is an alternative for people who may not be candidates for ciprofloxacin, such as children.
These drugs can cause side effects, and long-term use can lead to the development of antibiotic-resistant strains of bacteria.
Problems with antibiotic resistance
In the past, the drug of choice was chloramphenicol. Doctors no longer commonly use it, however, because of side effects, a high rate of health deterioration after a period of improvement (relapse) and widespread bacterial resistance.
In fact, the existence of antibiotic-resistant bacteria is a growing problem in the treatment of typhoid fever, especially in the developing world. In recent years, S. typhi also has proved resistant to trimethoprim-sulfamethoxazole and ampicillin.
Other treatments
Drinking fluids: This helps prevent the dehydration that results from a prolonged fever and diarrhea. If you’re severely dehydrated, you may need to receive fluids through a vein (intravenously).
Surgery: If your intestines become perforated, you’ll need surgery to repair the hole.
Prevention
Preventing typhoid is all about avoiding contaminated food and water. The same healthy practices will also help protect you from diseases such as cholera and hepatitis A, which are transmitted in the same way. Follow these guidelines to minimize your risk:
Boil or disinfect all water before drinking it – use disinfectant tablets or liquid available in pharmacies or drink commercially bottled (preferably carbonated) beverages.
Peel all fruit and vegetable skins before eating.
Keep flies away from food.
Watch out for ice cubes, ice cream, and unpasteurized milk, which can easily be contaminated.
Cook all food thoroughly and eat it while it’s hot.
Be aware of the “danger foods” shellfish, salads, and raw fruit and vegetables.
Do not eat food or drink beverages from street vendors.
At present, vaccinations against typhoid provide about 50% protection for 3 to 7 years – the duration of protection depends on the vaccine used. The vaccine is available as an oral capsule and as an injection. Your doctor will determine what form is best for you or your children. Even vaccinated people must follow the food safety tips listed above. It is best to be immunized at least 7 to 14 days before possible exposure (depending on the vaccine used).