Introduction
Background
Typhoid fever is a bacterial illness caused by Salmonella typhi, also known as Salmonella enterica serotype Typhi, a gram-negative rod found only in humans. This illness is characterized by persistent fever, abdominal pain, severe anorexia, constipation or mild diarrhea, and delirium. Most cases in the United States are acquired abroad and involve children, adolescents, and young adults. A similar, but less severe, disease is caused by Salmonella paratyphi A. Ocular manifestations are rare in typhoid fever.
Pathophysiology
Following ingestion of an infectious dose of at least 10,000 bacteria, mucosal penetration occurs in the distal ileum resulting in a transient, asymptomatic bacteremia. The organisms survive and multiply within mononuclear phagocytes located in lymph nodes, spleen, liver, and bone marrow.
The clinical phase of the disease begins within 1-3 weeks, resulting from persistent bacteremia. Hematogenous spread to ileal Peyer patches and the gall bladder reintroduces bacteria to the gut lumen and stool cultures again become positive, allowing continued fecal-oral spread of the disease. Mucosal ulceration overlying hyperplastic Peyer patches in the ileocecal region may result in pain, diarrhea, bleeding, and occasional perforation.
Frequency
United States
Approximately 500 cases of typhoid fever are reported annually in the United States. More than two thirds of those cases are contracted during travel abroad, most commonly to the Indian subcontinent. Most cases acquired in the United States are the result of local outbreaks or occur in patients with underlying medical disease. For example, the rate among patients with HIV is 60 times greater than the general population. The risk for travelers is less than 1 case in 10,000 trips, but this risk increases to 4 cases in 10,000 trips to high-risk countries.
International
According to the World Health Organization 2004 census, approximately 21.6 million cases occur per year worldwide, mostly in Asia, Africa, and Latin America, with 200,000 fatalities. Global incidence is about 0.5%, but incidence rates as high as 2% have been reported in hot spots, such as Indonesia and Papua New Guinea, where typhoid fever ranks among the 5 most common causes of death. In these countries, 91% of cases involve children aged 3-19 years, and 20,000 deaths occur per year.
Mortality/Morbidity
- The introduction of chloramphenicol reduced the case fatality rate from 12% to 4%, although this figure remains over 10% in the developing world despite antibiotic availability. Altered mental status has been associated with a high case-fatality rate.
- Most symptoms resolve without antibiotics within 3 weeks of onset in the majority of patients. Rare fatal complications include intestinal perforation or severe hemorrhage. Localized infections such as cholangitis, urinary tract infection, pneumonia, osteomyelitis, arthritis, meningitis, and endophthalmitis occasionally are seen. Spontaneous splenic rupture and multiple brain abscesses also have been reported.
- Relapse occurs in as many as 10% of patients, while 1-3% of patients become long-term carriers following recovery.
Race
No reported racial predilection exists.
Sex
Both genders appear equally susceptible.
Age
Typhoid fever affects adults and children of all ages.
Clinical
History
- US travelers abroad have about a 1 in 10,000 risk of contracting typhoid fever, but this risk increases several fold when visiting countries with endemic typhoid.
- Symptoms develop gradually in most cases with maximal severity occurring during the second or third week following exposure.
- Constitutional symptoms include fever, chills, headache, sore throat, muscle pain, and weakness.
- Many patients complain of a skin rash and cervical adenopathy.
- Gastrointestinal symptoms include nausea, vomiting, anorexia, diarrhea, constipation, and abdominal pain.
- Neurologic symptoms include altered mental status and occasional seizures.
- Patients with ocular manifestations generally complain of pain and decreased vision.
- Recovery is characterized by diminishing fever and begins by the fourth week in patients without antibiotic treatment. In contrast, antibiotic use usually results in defervescence in less than 7 days.
Physical
- Relative bradycardia (less tachycardia than expected for the degree of fever) may occur in up to 50% of patients but is not a reliable diagnostic indicator.
- Faintly erythematous maculopapules or rose spots occur on the trunk and may become hemorrhagic.
- Cervical adenopathy and hepatosplenomegaly are often present.
- Intestinal bleeding may occur from ulceration of mucosa overlying hyperplastic ileal Peyer patches.
- Altered mental status and seizures may occur.
- Ocular manifestations are rare and occur in association with systemic illness.
- These manifestations may include lid abscesses, corneal ulcers, uveitis, vitreous hemorrhage, retinal hemorrhage or detachment, optic neuritis, extraocular muscle palsies, orbital thromboses, and orbital abscesses.
- Most of the ocular complications probably result from direct invasion by the organism into ocular tissues.
Causes
- Typhoid fever is most prevalent in developing countries where sanitary water and sewage systems are lacking. Transmission occurs most often by one of the following mechanisms:
- Ingestion of contaminated food or water
- Contact with an acute case of typhoid fever
- Contact with a chronic asymptomatic carrier
- Other diagnostic considerations
- The differential diagnosis of infectious diseases depends on whether the patient has been traveling recently outside the United States.
- Involvement of a specialist in infectious disease is strongly encouraged. In addition, noninfectious cases of febrile illness, such as lymphoma, also should be considered.
More on Typhoid Fever |
 Overview: Typhoid Fever |
| Differential Diagnoses & Workup: Typhoid Fever |
| Treatment & Medication: Typhoid Fever |
| Follow-up: Typhoid Fever |
| References |
| Next Page » |
References
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Further Reading
Keywords
enteric fever, Salmonella typhi
