Q: I am a registered nurse and physician assistant in USA. I am trying to counsel a patient who has been attending school in a third world country where typhoid is endemic and she has been exposed to 3 other students who, in the past 2 days, have tested positive by Typhi dot-M for S. typhi. Two are symptomatic, and one is not, except for an upper respiratory infection. What is the exact course of the disease? I have read conflicting descriptions that it begins with diarrhoea in the incubation phase; it can last for 1-2 weeks, then the diarrhoea stops and active disease phase starts with high fever, abdominal pain, anorexia and constipation that can last for several weeks. I have also heard that typhoid starts out with a fever and diarrhoea or constipation, which continues throughout the disease. There is no incubation period of being asymptomatic and then, active disease starts. Is there any value in using the Typhidot, IgG level, as an assessment tool for carrier status in the absence of S. typhi isolated in stool culture?

A:The incubation period of typhoid fever varies with the size of the infecting dose and averages 7-14 (range, 3-60) days; 1-10 days for paratyphoid fever. During the incubation period, 10-20% of patients have transient diarrhoea (enterocolitis) that usually resolves before the onset of the full-fledged disease. As bacteraemia develops, the incubation period ends. Symptoms develop gradually in most cases with maximal severity occurring during the second or third week following exposure. Constitutional symptoms include chills, dull frontal headache, sore throat, muscle pain, and weakness before the onset of fever. Gastrointestinal symptoms include nausea, vomiting, anorexia, diarrhoea or constipation, and abdominal pain. About 20-40% of patients present with abdominal pain. Constipation is common in immunocompetent adults and is most likely due to hypertrophy of Peyer patches. Young children and immunocompromised individuals are more likely to have diarrhoea that is probably due to blunted secondary immunity. The incidence of constipation versus diarrhoea varies geographically, perhaps because of local differences in diet or S. typhi strains, or genetic variation. Most of the classic signs and symptoms of typhoid fever are prevented with prompt treatment. Clinical response begins about 2 days after starting antibiotics, and the patient's condition markedly improves within 4-5 days. The best modality of diagnosis is blood culture in the initial period followed by stool, urine or bone marrow culture later. The Typhidot or IgG levels or the widal test have limited role in the diagnosis. They provide limited information, which is affected by the treatment, immune status of the individual, infective dose, and being surrogate markers, have many modifiers.