Typhoid Fever: A Reemerging Threat?
By Amesh A. Adalja, MD, September 3, 2010
In the U.S., Salmonella is known chiefly for causing gastroenteritis and sparking recalls of food products—most recently eggs. However, organisms of the Salmonella genus also cause the more serious illness typhoid (or enteric) fever.
Nine Recent Cases in the U.S.
While typhoid fever is rare in the U.S., where 400 or fewer cases occur per year, it made headlines in August after 9 cases in California and Nevada were reported to the U.S. Centers for Disease Control and Prevention (CDC).1 All cases occurred in Hispanic patients, of median age 21, with disease onset occurring between April 10 and July 25, 2010. Only 1 of the 9 had traveled outside of the country. No fatalities have occurred to date, and clinical course has not been reported for any of the patients.
Salmonella Typhi lives exclusively in humans. S.Typhi, like other types of the bacterium, is spread via the fecal-oral route. This was the case with the New York City cook dubbed “Typhoid Mary,” a carrier who infected so many through her work that the U.S. government quarantined her in 1907 and again in 1915.
After CDC investigators linked the majority of the current cases to the consumption of frozen mamey, a fruit pulp product that is used in milkshakes and smoothies, some news reports began referring to the culprit in these 9 cases as “Typhoid Mamey.” Mamey is a tropical fruit grown in South and Central America. Mamey products from 2 companies have been recalled (Goya Foods, Inc., Montalvan’s Sales, Inc.).
Typhoid Fever Disease
After a person is infected with the S.Typhi organism, the bacterium disseminates throughout the body. Systemic illness follows a 10- to 14-day incubation period and is characterized by fever, abdominal pain, and nonspecific symptoms; diarrhea or constipation may be present. The classic rose spot rash occurs in approximately 30% of cases. Severe disease manifestations include gastrointestinal bleeding, gastrointestinal perforation, Guillain-Barré syndrome, and death, which occurs in 0.4% of cases in the U.S.2
Diagnosis is made by standard culture of the organism from a sterile site (including bone marrow) or from stool, or through biopsy of a rose spot. Serology can also be used for diagnosis. Up to 4% of those infected become chronic carriers (and spreaders) of the bacteria.
Treatment and Vaccination Can Control Disease
Two types of vaccines are available for prevention of typhoid fever: one is a live, attenuated oral vaccine; the other is an injectable capsular polysaccharide vaccine. Both are used in travelers to countries where typhoid is endemic.
Antimicrobial therapy directed by susceptibility testing is effective at reducing the complications of typhoid fever. Fluoroquinolones, azithromycin, and ceftriaxone are all employed, depending on antibiotic resistance, which has reached high levels in some parts of the world. In the U.S., more than 40% of S.Typhi isolates demonstrate decreased susceptibility to the fluoroquinolone ciprofloxacin.
An Emerging Infectious Disease in the U.S.
That typhoid has reemerged in the U.S. underscores the very real threat of emerging infectious diseases and should prompt clinicians to acquire the knowledge to identify such diseases, initiate prompt therapy, and report the incident. The recently reported typhoid cases—along with cases of hepatitis A, cyclospora, salmonella gastroenteritis, and listeria—also highlight the vulnerability of the global food supply chain to contamination with serious pathogens.
CDC. Investigation Update: Multistate Outbreak of Human Typhoid Fever Infections Associated with Frozen Mamey Fruit Pulp. http://www.cdc.gov/salmonella/typhoidfever/#general. Accessed August 26, 2010.
Pegues DA, Miller SI. Salmonella species, including Salmonella Typhi. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, PA: Churchill Livingstone; 2010.