DENGUE DISPATCHES Recognition of leptospirosis is especially important since antimicrobial agents can reduce its severity and duration (13). Leptospirosis patients identified in Dhaka were impov- erished and poorly educated. This may reflect more fre- quent exposure to environments contaminated with urine from rodents or other animals. In contrast, dengue patients came from households with higher incomes and levels of education. Whether these socioeconomic differences reflect differing patterns of disease can only be determined by future population-based studies, which may in turn shed light on optimal prevention strategies. Most of the patients hospitalized with leptospirosis and dengue virus infection in Dhaka during the period of this study were male. A recent seroprevalence study in Bangladesh did not demonstrate a sex difference in dengue seropositivity (14), but leptospirosis has been reported predominantly in men in other regions (15). Further prospective research would be useful to better define the clinical spectrum and gender distribution of disease in Bangladesh. This study has a number of limitations. Only acute- phase serum samples were obtained as part of the hospital- based dengue surveillance program in Bangladesh. Serologic diagnosis of leptospirosis with a single specimen obtained early in infection is limited; hence, we used Leptospira-specific PCR for diagnosis in our study popu- lation. Although this molecular technique is highly sensi- tive and specific for the presence of leptospiremia (7), more cases may have been detected through the use of microscopic agglutination testing on paired serum sam- ples. Notably, less than one-third of the patients with a diagnosis of leptospirosis by PCR had detectable levels of Leptospira-specific IgM. This is likely due to the sampling of acutely ill patients before seroconversion. In support of this, leptospirosis patients who had detectable levels of IgM exhibited a trend toward longer duration of fever compared with those who did not have detectable levels (6.5 vs. 5.5 days, p = 0.12). Some cases of leptospirosis resulted in death, and the case-fatality rate among leptospirosis patients was signifi- cantly higher than among dengue fever patients. The dif- 768 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 5, May 2005