Incubation Period of Enteric Fever

The incubation period of enteric (typhoid) fever is typically seven to 18 days, with a range of three to 60 days. 1

Epidemiology and Transmission

Enteric fever is caused by human-restricted bacteria Salmonella enterica serovar Typhi (typhoid) and Salmonella enterica serovar Paratyphi A, B, and C (paratyphoid) 2
Transmission occurs via the fecal-oral route, primarily in areas lacking safe water, sanitation, and hygiene infrastructure 2
Enteric fever is the most common serious tropical disease requiring treatment in travelers returning from Asia, though it is relatively uncommon in Africa 1
The highest incidence is found in south central Asia and South East Asia (>100 cases per 100,000 person years) 1
In the United States, 80% of reported cases are typhoid and 20% are paratyphoid A, with the proportion of paratyphoid A increasing in recent years 3

Initial symptoms typically include a gradual fever onset over 3-7 days with malaise, headache, and myalgia 2
Blood culture remains the reference standard diagnostic method despite low sensitivity, with up to 80% sensitivity in the first week of illness 1
Life-threatening complications can arise in the second week of untreated illness 2
Complications may include:
- Central nervous system manifestations (encephalopathy, meningitis, seizures) 4
- Myocarditis 4
- Hepatitis 4
- Gastrointestinal bleeding 4

Blood cultures are the primary diagnostic method, with highest sensitivity (up to 80%) in the first week of illness 1
Newer rapid serological tests detecting IgM against specific antigens (e.g., Typhidot, Typhidot-M, Tubex) have been developed but show mixed results 1
Differential diagnosis should include other causes of fever in returning travelers, with malaria being the most important to exclude first 1

For clinically unstable patients, empiric treatment with ceftriaxone is recommended pending blood culture results 1
For patients who have traveled from sub-Saharan Africa, ciprofloxacin remains an alternative 1
For confirmed cases:
- If sensitive, switch to ciprofloxacin 1
- If resistant, use azithromycin as an oral follow-on agent 1
Treatment should be continued for 14 days to reduce risk of relapse 1
Increasing resistance to fluoroquinolones, particularly among travelers to south and southeast Asia, is a growing concern 1, 2

Three vaccine types are available for prevention of typhoid disease, including newer typhoid Vi-conjugate vaccines 2
Water, sanitation, and hygiene measures are cornerstones of prevention 2

The incubation period knowledge is critical for:
- Identifying potential exposure sources
- Contact tracing in outbreak scenarios
- Determining appropriate monitoring periods for exposed individuals
Always consider enteric fever in travelers returning from endemic regions, particularly south and southeast Asia, who present with fever 1
Remember that previous antimicrobial use may alter the typical presentation 2