Endemic Typhus in Singapore - A Re-Emerging Infectious Disease?

AKY Ong, PA Tambyah, S Ooi, G Kumarasinghe, C Chow
Correspondence: Dr Paul Ananth Tambyah, mdapat@nus.edu.sg

ABSTRACT
Singapore is a modern urban city and endemic typhus is thought to be a disease of the past. This may be due to lack of specific serological testing as indirect immunoperoxidase testing using specific rickettsial antigens (U.S. Army Medical Research Unit, Institute of Medical Research, Kuala Lumpur, Malaysia) has only recently become available. In the last fourteen months, twenty-one cases of endemic typhus were diagnosed in patients hospitalised for acute febrile illnesses at the National University Hospital. We conducted a case control study to define the clinical and laboratory features of endemic typhus in Singapore.
Method Demographic, clinical and laboratory data were reviewed for cases and twenty-one age and sex matched controls who had negative serologic tests as part of a work-up for fever of unknown origin.
Results Apart from a higher initial temperature (39 degrees C vs 37.9 degrees C (p < 0.001)) and ALT(p = 0.002), cases and controls had similar presentations of fever, myalgia, headache, cough, normal WBC and platelet counts. Singapore residents and migrant workers were represented in both groups (p = ns).
Conclusion Endemic typhus remains an important cause of acute febrile illness in Singaporein both the local and migrant worker populations. The presentation is similar to other causes of acute febrile illnesses and the diagnosis will be missed unless it is specifically sought.

Keywords: endemic typhus, rickettsial disease, fever of unknown origin
Singapore Med J 2001; 42(12): 549-552