Did you know? Typhoid Mary was an actual person in the early 1900s who was an asymptomatic (without symptoms) carrier of Salmonella typhi. During her career as a cook, she unknowingly infected 47 people with typhoid fever and was eventually quarantined after she refused to heed warnings from public health officials and stop cooking.
Species Name: Salmonella typhi is the most common species that causes Typhoid Fever. Other species, including Salmonella enteritidis or Salmonella typhimurium, can cause gastroenteritis (diarrhea) or typhoid-like diseases.
Type of Microbe: Gram-negative bacteria
How it spreads: Salmonella typhi can be shed from people with typhoid fever, as well as from carriers, who are individuals who have recovered from the disease but continue to carry and shed the bacteria in their feces. Infection occurs through ingestion of foods or drinks contaminated with Salmonella typhi, including water used for drinking or washing foods.
Who’s at risk? Typhoid fever is more common in unindustrialized countries, especially Asia, Africa, and Latin America. About 400 cases occur each year in the United States, the majority of which are acquired during international travel. In developing countries, 21.5 million people are affected yearly.
Symptoms: High fever of 103 F to 104 F, abdominal pain, headache, loss of appetite
Diagnosis: Blood or stool culture. Bone marrow aspirate is also a sensitive, but more invasive, method used for diagnosis.
Prognosis: With antibiotic treatment, symptoms start to ease within 2 to 3 days, and the prognosis is generally good. Without treatment, fever may last for weeks to months, and the disease is fatal in up to 20% of afflicted individuals.
Treatment: Antibiotics (ampicillin, trimethoprim-sulfamethoxazole, or ciprofloxacin) are usually prescribed. The selection of antibiotics depends on the pattern of antibiotic-resistance in the location where the infection was acquired.
Prevention: Two vaccines available in the United States for typhoid fever: an oral vaccine (Vivotif Berna) and an injected vaccine (Typhim Vi). If you are traveling to a developing country where typhoid fever may be a problem, see your healthcare provider for a vaccination at least 1 week before you travel. Even if you’ve been vaccinated in the past, a booster may be needed. In addition, practice safe eating habits while traveling. Drink only bottled or boiled water, eat only hot, thoroughly cooked foods, and only eat raw fruits and vegetables that have been both washed and peeled.
How it causes disease: Anywhere from one week to one month after Salmonella typhi is ingested, it invades the intestines, multiplies, and spreads into the bloodstream. The bacteria can then spread to the spleen and liver, where they multiply even more, re-entering the bloodstream, causing illness and spreading to the gall bladder and back to the intestine, where severe damage to the intestines occurs.
Symptoms of typhoid fever are believed to be caused by an immune response to massive amounts of lipopolysaccharide (LPS), which is a toxic component of the bacterial surface. The immune system releases proteins called cytokines which activate a strong inflammatory response against the bacteria. Once the bacteria enter the bloodstream, the immune response circulates to all tissues and organs throughout the body and can be fatal without antibiotic treatment.
Complications: In addition to risk of death or persistent infection, other potential consequences of Salmonella typhi infection include liver damage, toxemia (bacterial toxins in blood), myocarditis (inflammation of the myocardium in the heart), and intestinal lesions may occur.
Sources:
Salmonella spp.. USFDA Bad Bug Book. Center for Food Safety and Nutrition.
Typhoid Fever. Centers for Disease Control and Prevention.
Salyers, AA and Whitt, DD. Bacterial Pathogenesis. A Molecular Approach. American Society for Microbiology. Washington, D.C. 1994. pp. 229-243.
