Potential Bioterrorism Agent: Category B
Hospital: Report by IDSS, facsimile, mail or phone
Lab: Report by IDSS, facsimile mail or phone
Physician: Report by IDSS, facsimile, mail or phone
Local Public Health Agency (LPHA): Follow-up required
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
Typhoid fever is caused by the bacillus Salmonella enterica subspecies enterica serovar Typhi (commonly S. Typhi).
B. Clinical Description
Symptoms: Typhoid fever causes fever, headache, malaise, anorexia, bradycardia, splenomegaly, and constipation more often than diarrhea in adults. Rose colored spots occur on the trunk in 25% of light-skinned patients and a nonproductive cough often occurs in the early stage of illness.
Onset: Illness is usually not abrupt and varies from mild illness with low-grade fever to severe clinical disease with abdominal discomfort and multiple complications. Inapparent or mild illnesses occur, especially in endemic areas.
Complications include intestinal perforation and hemorrhage, kidney failure, and peritonitis. The case-fatality rate of 10-20% observed in the pre-antibiotic era falls below 1% with prompt antibiotic therapy. Relapses may occur in 15-20% of patients with typhoid fever.
A major concern with typhoid fever is that a carrier state may follow illness. Typhoid fever can be present in both feces and urine chronically after acute infection. The chronic carrier state is most common (2-5%) among persons infected during middle age. Carriers frequently have biliary tract abnormalities including gallstones. The chronic urinary carrier state may occur with schistosome infections.
Common reservoirs: Humans may become transient or permanent carriers.
D. Modes of Transmission
Spread: Via ingestion of food and water contaminated by feces and urine of patients and carriers. Important vehicles for transmission include shellfish (particularly oysters) from sewage contaminated beds, raw fruit, vegetables fertilized by human feces, contaminated milk/milk products and unidentified cases. Flies may contaminate foods, allowing the organism to multiply to infectious doses. Epidemiological data suggest that waterborne transmission may involve less contamination than foodborne transmission.
E. Incubation period
Depending on the inoculum size and host factors, the incubation period may range from 3 to over 60 days. The usual range is 8-14 days.
F. Period of Communicability or Infectious Period
The disease is communicable for as long as infected persons excrete the bacilli in their stool or urine, usually from the first week throughout convalescence; variable thereafter. Approximately 10% of untreated typhoid patients discharge bacilli for 3 months after symptom onset; 2-5% become carriers.
Typhoid fever has a worldwide distribution, with approximately 5700 cases per year in the United States, with approximately 75% of these cases occurring among travelers to other countries. An estimated 27 million cases of typhoid fever and 210,000 deaths occur worldwide.
H. Bioterrorism Potential
Category B Agent: As with other Salmonella organisms, S. Typhi has potential to be used as a bioweapon similar to other fecal-oral transmission agents.
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Typhoid Fever can be found at: www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis.htm#top
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
CDC web site, Typhoid Fever. www.cdc.gov/nczved/divisions/dfbmd/diseases/typhoid_fever/
Heymann, D.L., ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.
IDPH web site: www.idph.state.ia.us/adper/
World Health Organization site: www.who.int/topics/typhoid_fever/en/