male. Patients with leptospirosis were of similar age and sex as patients with dengue (Table 1). Patients with lep- tospirosis had less education and came from households with lower income than patients with dengue. The peak occurrence of leptospirosis was in October and November, shortly after the monsoon season in Bangladesh. This overlapped with the period of highest dengue activity (July through December) (Figure). Patients with leptospirosis reported a slightly longer duration of fever than patients with dengue (Table 2). While most patients with dengue or leptospirosis had con- tinuous fever, an intermittent fever was more likely with leptospirosis. Reports of rash were more common with dengue fever. Aside from fever and rash, the symptoms of patients with leptospirosis and dengue were similar (Table 2): headache, myalgia, nausea, and vomiting were most common. The median temperature and heart rate at physical examination were higher in leptospirosis patients than in dengue patients. Evidence of bleeding, including petechial rash, positive tourniquet test result, and gum bleeding, were more common in patients with dengue, although they were also found in some patients with leptospirosis. Subconjunctival hemorrhage, which may have been con- fused with conjunctival inflammation, was more common- ly reported in patients with leptospirosis. Hepatomegaly and jaundice were more common in leptospirosis patients, but this difference was not statistically significant. On laboratory examination, total leukocyte counts were similar in patients with dengue and patients with lep- tospirosis; however, lymphocytes were more likely to be predominant in patients with dengue. Hemoconcentration and thrombocytopenia were associated with dengue fever. Of the patients whose outcome was known, 3 (5%) patients with leptospirosis died, compared with 11 (1.2%) patients with dengue (p = 0.048). Antimicrobial therapy Leptospirosis during Dengue Outbreak, Bangladesh Figure. Proportion of dengue and leptospirosis patients at 2 major hospitals in Dhaka, Bangladesh, by month, 2001. for leptospirosis was not provided, and data on the cause of death were not available. The patients who died of lep- tospirosis were younger than those who died of dengue (24 ± 6 years of age vs. 36 ± 9 years, p = 0.05). Conclusions This is the first description of disease caused by Leptospira in urban Bangladesh. Our findings indicate that leptospirosis causes serious febrile illness in the densely populated city of Dhaka. Studies conducted in other dengue-endemic areas have shown that leptospirosis can be confused with dengue fever (10–12). Most clinical symptoms of leptospirosis patients in Dhaka were nonspecific and not distinguishable from symptoms associated with dengue fever or other viral illnesses. Although fever in leptospirosis patients was higher and of longer duration than in dengue patients, there is sufficient overlap of clinical findings to suggest that cli- nicians caring for patients in Bangladesh should maintain a high index of suspicion for both diseases, especially dur- ing the peak incidence seasons that follow the monsoons. Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 11, No. 5, May 2005 767