Leptospirosis in the Andaman Islands, India

Leptospirosis is an emerging zoonosis. In the Andaman Islands during the early twentieth century, it occurred in the penal settlements of the British India Administration, mostly as Weil's disease, an acute febrile illness with hepato-renal complications. It was caused by leptospires belonging to groups Akiamy A and Andamans A. After the 1930s nothing further is known regarding the disease until the late 1980s, when Andaman haemorrhagic fever (AHF), a mysterious illness with the majority of cases presenting pulmonary involvement, appeared. AHF was later identified as leptospirosis and severe pulmonary haemorrhage was shown for the first time as a complication of leptospirosis from India. Leptospirosis continues to occur in the Islands annually. It generally presents as two separate clinical syndromes: the hepato-renal form, and the pulmonary form, which is associated with high case fatality rates ranging from 10 to 15%. Infections are due to a variety of serovars, Valbuzzi being the commonest. Leptospira interrogans sensu stricto has been the predominant infecting species. Doxycycline has been shown to confer a beneficial effect in reducing the clinical illness and mortality during outbreaks. The history of leptospirosis in the Islands, its epidemiology, clinical spectrum, characteristics of the isolates and control are reviewed and discussed in this article.     

Epidemiology of leptospirosis in New Caledonia (South Pacific): a one-year survey

We describe a series of 144 cases of leptospirosis diagnosed in 1989 in New Caledonia. The incidence rate was 90 per 100,000 person-years, with a specific mortality rate of 4% patients. Those affected (100 males, 44 females) were mainly aged 20 to 40 years. Incidence in rural areas (112 per 100,000 person-years) was seven times higher than in urban settlements. Two periods with higher incidence were noticed corresponding to highest rainfall. Twenty-nine of the cases occurred in individuals with professions commonly associated with leptospirosis. Contacts with rats, dogs and ditch or river water were the most frequently mentioned. The clinical expression of the disease was polymorphic: 60% of the patients had mild symptoms, 40% were acute forms including Weil's disease. Of 57 hospitalized, 23% were admitted with an initial diagnosis of dengue, and 37% with leptospirosis. Main clinical syndromes were: icterus and/or renal syndrome in 50% of patients, cardiac syndrome in 65%, acute myalgies in 58% and pulmonary syndrome in 50%. Although hemorrhages were uncommon (17%), 40% of the cases demonstrated thrombocytopenia (< 50,000/m³). Pancreatic involvement with hyperamylasemia was evidenced in 50% of cases. Twelve serogroups of Leptospira were implicated, icterohaemorragiae predominated (41%), but was not associated with severe forms. In New Caledonia, like in all tropics, leptospirosis must be considered as an environmental disease, professional activities being just an additional risk factor. Use of serology as a reliable tool for confirmation of cases in areas of high environmental contamination is discussed.     

Phylogenetic relatedness among leptospiral strains belonging to same serovar recovered from patients with different clinical syndromes.

Leptospirosis is an emerging zoonotic disease with widespread distribution. The disease, caused by a large number of pathogenic serovars of leptospires, varies in severity from mild flu like illness to severe and fatal forms. It has often been observed that the strains of the same serovar are associated with different clinical syndromes. In this study the isolates recovered from patients with mild and severe form of leptospirosis and those isolated from rodents trapped in the same areas were analyzed by using random amplified polymorphic DNA (RAPD) fingerprinting method using the primers PB1, M16, B11 and B12. RAPD fingerprinting patterns of these strains consistently showed five different genetic clusters. Strains belonging to serovar Ratnapura that caused hepato-renal involvement in patients in South India were genetically dissimilar to strains of the same serovar isolated from patients in Andamans who had pulmonary complications. Strains of other serovars causing mild and sever illness could also be discriminated. However, isolates obtained from human patients and rodents in the same geographical areas showed identical fingerprint patterns indicating that strains circulating in different geographical regions, though belonging to same serovar, are unique to each region.     

Pulmonary haemorrhage as a predominant cause of death in leptospirosis in Seychelles

We examined the cause of death during a 12-month period (1995/96) in all consecutive patients admitted to hospital with leptospiral infection in Seychelles (Indian Ocean), where the disease is endemic. Leptospirosis was diagnosed by use of the microscopic agglutination test and a specific polymerase chain reaction assay on serum samples. Seventy-five cases were diagnosed and 6 patients died, a case fatality of 8%. All 6 patients died within 9 days of onset of symptoms and within 2 days of admission for 5 of them (5 days for the 6th). On autopsy, diffuse bilateral pulmonary haemorrhage (PH) was found in all fatalities. Renal, cardiac, digestive and cerebral haemorrhages were also found in 5, 3, 3 and 1 case(s), respectively. Incidentally, haemoptysis and lung infiltrate on chest radiographs, which suggest PH, were found in 8 of the 69 non-fatal cases. Dengue and hantavirus infections were ruled out. In conclusion, PH appeared to be a main cause of death in leptospirosis in this population, although haemorrhage in other organs may also have contributed to fatal outcomes. This cause of death contrasts with the findings generally reported in endemic settings.     

Recent trends in human leptospirosis in Italy

The recent epidemiological trends of human leptospirosis in Italy were investigated using data collected for the years 1981–1985. A total of 626 hospitalized patients with clinical diagnoses of suspected leptospirosis were reported by hospital centers from several Italian regions. Epidemiological, clinical and seroimmunological data were collected in 517 of these cases and examined by the National Center for Leptospirosis.Serological findings in 33.5% of these subjects met the criteria for confirmation of the disease. In 21.8% of the subjects, low titer antibodies were detected, which possibly reflected previous leptospiral infections. An early antibiotic treatment of the current infection may also have lowered the seroimmunological response in some of these patients.In 59.3% of the confirmed cases, modes of transmission were allotted equally between accidental events and recreational or occupational activities. Drinking water from an open air fountain emerged as an uncommon mode of transmission; it was responsible for an outbreak of 33 cases of leptospirosis. In another 37.07% of the subjects, it was impossible to establish the mode of transmission.Respiratory or influenza-like symptoms were the only clinical signs of illness in 21.2% of the patients with confirmed leptospirosis.In comparison to the sixties and seventies, the prevalence of infecting serovars showed increasing incidence of infections due to serovars of the Javanica (11.0%) and Australis (11.0%) serogroups and an important decrease in the Bataviae serogroup infections (from 58.8% in rice-field workers in the forties to 0.6% in the years 1981–1985). Sejroe serogroup infections accounted for 4.5 per cent of confirmed cases of leptospirosis.In 49.7% of subjects with confirmed leptospirosis, cross-agglutination at the same titre with two or more serovars of different sero-groups occurred, thus preventing the identification of the serogroup of the infecting strain.     

Persistence of anti-leptospiral IgM,IgG and agglutinating antibodies in patients presenting with acute febrile illness in Barbados 1979-1989

The persistence of anti-leptospiral IgM and IgG antibodies and agglutinating antibodies was studied in serologically confirmed cases of severe leptospirosis during the acute illness and over periods of several years after recovery. The antibody response in non-leptospirosis patients presenting to hospital with similar symptoms over the same period of time was used to estimate the background antibody level to leptospirosis in the community. All patients enrolled in the study had blood samples collected twice in the acute stage of illness, once during convalescence and then annually from the time of initial hospitalisation until the end of the study period. Six hundred and thirty-eight patients presented to hospital with acute febrile illness, of whom 321 were diagnosed with leptospirosis. Patients who had severe leptospirosis commonly remained seropositive, with IgM, IgG and agglutinating antibodies detectable for several years after infection. A significant proportion of cases had high titres of agglutinating antibody detectable by the microscopic agglutination test ( 800). There were marked differences in the magnitude and duration of persistence of agglutinating antibodies directed against different serogroups. More than 20% of cases with evidence of infection with serogroup Autumnalis retained titres of > 800, 4 years after the acute illness. In one case a titre of 800 was detected 11 years after infection. Persistence of agglutinating antibody titres can create problems in interpretation of serological results and make it impossible to estimate the time of infection, given a specific titre. This study demonstrates that in endemic areas where seroprevalence is high, use of a single elevated titre is not reliable to define a current infection.     

Epidemiological trend of human leptospirosis in Italy between 1994 and 1996

In the three-year period 1994–1996, 222 reports on human cases of leptospirosis were received by the Italian Ministry of Health. The average annual number of reports was 29.2% lower than in the preceding eight years. In all cases but two the infections were thought to have been acquired in Italy. As in previous years, the majority of cases was observed in the northern regions of the country (83.8%), mostly in males (88.9%). Cases occurred in all age groups, but were more common in the working-age population (15–64 years). There was no common-source outbreaks. The typical leptospiral seasonal course, with a peak in August, was observed. During 1994, leptospirosis was the reported cause of death in 19 patients. Mortality was higher among males than females. The overall fatality rate was 22.6%. During the study period, a total of 126 cases of leptospirosis were confirmed by the National Centre for Leptospirosis or one of the 12 Regional Leptospira Laboratories. Of the 103 patients for whom information on place of residence, contact with animals, occupational and recreational activities was available, 98 (95.1%) were people who live in rural areas or devote themselves to occupational or recreational activities at risk. The likely source of infection and the mode of exposure were known for 55 patients. Forty-five patients (81.8%) were likely infected by contaminating water (43 cases) or soil (2 cases), ten (18.2%) by direct contact with animals or animal urine. Both running (51.2%) and stagnant water (27.9%) have been reported as a source of infection. Rodents were implicated in 50.0% of the 10 cases involving animals. In comparison with the preceding eight-year period, the risk of contracting leptospirosis was found to have increased for recreational activities (from 34.7 to 38.2%) and decreased for occupational activities (from 45.8 to 32.7%). A large number of infections, however, was ascribed to accidental events (25.5%). As in the previous period, besides fever, the involvement of the liver was the most frequent clinical manifestation (70.8%). Influenza-like symptoms were the only signs of illness in 15.1% of cases. Infections by 9 different serogroups were detected. The most frequent antibodies were those against serovars icterohaemorrhagiae, poi, copenhageni and bratislava. The presence of co-agglutinins against serovars belonging to different serogroups prevented the identification of the presumptive infecting serogroup in 19.8% of subjects.     

Infective endocarditis in a district general hospital.

Thirty-three cases of infective endocarditis presenting during a 6.5 year period to a district general hospital were analysed retrospectively. The annual incidence was 22 cases per million population. Twenty-two cases had pre-existing cardiac disease, mainly valvular disease-usually rheumatic (nine cases) and prosthetic valves (10 cases). Recognizable precipitants such as recent surgery were uncommon. Two cases presented after deliberate drug overdose possibly due to depression exacerbated by systemic disease. Symptoms were usually non-specific. All but two cases had murmurs and most were pyrexial. Splinter haemorrhages and clubbing were seen in about 20% of cases. Viridans-type streptococci were the commonest infecting organisms (14 cases). Staphylococcal infection (six cases) was confined to intravenous drug abusers and patients with prosthetic valves. Five cases were culture negative. Cardiac failure was present in 13 cases at presentation and developed in seven others during treatment. Acute valve replacement was necessary in eight cases, and late replacement in three. Renal impairment (plasma urea > 8 mmol/l and/or plasma creatinine > 120 mumol/l) occurred in 19 cases during the course of their illness. Embolic phenomena occurred in 12 patients and mostly involved the central nervous system. In the 8 fatal cases, the cause of death was cardiac failure in six, cerebrovascular accident in one, and myocardial infarction in one. Four of the six patients who subsequently died of cardiac failure had been referred for surgery. Both those who were not referred had coexisting medical problems. Factors associated with increased mortality were age, male sex, cardiac failure (P < 0.01), renal impairment (P < 0.05), and embolic phenomena (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiac involvement in leptospirosis

Leptospirosis is a neglected global disease with significant morbidity and mortality. Cardiac complications such as chest pain, arrhythmias, pulmonary oedema and refractory shock have been reported in patients with severe disease. However, the frequency and extent of cardiac involvement in leptospirosis, are under-reported and poorly understood. Multiple factors may contribute to clinical manifestations that suggest cardiac involvement, causing diagnostic confusion. A variety of electrocardiographic changes occur in leptospirosis, with atrial fibrillation, atrioventricular conduction blocks and non-specific ventricular repolarization abnormalities being the most common. Electrolyte abnormalities are likely to contribute to electrocardiographic changes; direct effects on Na(+)-K(+)-Cl(-) transporters in the renal tubules have been postulated. Echocardiographic evidence of myocardial dysfunction has not been adequately demonstrated. The diagnostic value of cardiac biomarkers is unknown. Histopathological changes in the myocardium have been clearly shown, with myocardial inflammation and vasculitis present in postmortem studies. Nonetheless, the pathophysiology of cardiac involvement in leptospirosis is poorly understood. Cardiac involvement, demonstrated electrocardiographically or clinically, tends to predict poor outcome. No specific therapies are available to prevent or treat cardiac involvement in leptospirosis; current management is based on correction of deranged homeostasis and supportive therapy. Evidence suggests that direct myocardial damage occurs in patients with severe leptospirosis, and further studies are recommended to elucidate its pathophysiology, clinical features and contribution to overall prognosis, and to identify appropriate diagnostic investigations and specific therapies.     

Human leptospirosis in Italy, 1986–1993

In the eight-year period 1986–1993, the Italian National Center for Leptospirosis and the Regional Leptospira Laboratories confirmed 312 cases of clinical leptospirosis by using the microscopic agglutination (MA) assay. The majority of cases was observed in Northern regions of the Country. Cases were reported in all age groups, but were most common in the working-age population. Of 312 cases, 291 (93.3%) occurred among males. The largest number of infections was ascribed to occupational activities (45.8%). The typical leptospiral seasonal course, with a peak during the summer, was observed. Involvement of the liver was the most frequent manifestation. Influenza-like symptoms were the only signs of illness in 11.1% of cases. Anti-leptospira antibodies, cross-reacting with two or more serovars, were found in 28.2% of sera. The most frequent serovar-specific antibodies were those againstpoi, icterohaemorrhagiae, bratislava, copenhageni andsejroe.     

Enquiry about the needs of children whose mothers are admitted to psychiatric hospitals

The objective of this study is to assess whether children's needs are taken into consideration in female patients who are admitted to an adult psychiatric hospital. A retrospective case note audit of 100 female inpatients aged between 18 and 55 years over a 6-month period were randomly selected. The medical and nursing case notes of patients with children aged between 0 and 17 were assessed using a proforma. The information collected on mothers consisted of diagnosis of illness, type of admission (whether voluntary or detained), duration of admission, previous psychiatric admissions, patient age, marital status, whether or not employed, relationship with partner, mental health of partner, history of violence, medical history of relevance, family history of mental illness, and whether other agencies were involved. Children data collected consisted of number of children per patient and their ages, an enquiry into the child's welfare, emotional and behavioural development, educational/cognitive development, physical health and development, relationship with family and peers, children's knowledge of parent's illness, alternative care arrangements for child during mother's admission and their relationship to carer, child's involvement in their parents' illness as a carer and actions taken on behalf of the child. Of the 100 patients, 62 had children aged between 0 and 17 years. There was an enquiry into children's welfare in 15 (24%) cases and an enquiry into children's knowledge of their parents' illness in three (4.8%). Actions were taken on behalf of children in 13 (21%) cases, in five cases this was not necessary as children resided elsewhere, and in one case a social work assessment was requested but no subsequent documentation of this being completed. There was no documentation of actions taken in the remaining 43 (69.4%) cases. The results of this retrospective case note audit suggest that children's welfare is not routinely enquired about in female patients admitted to psychiatric hospitals. Actions taken on behalf of children occurred often when there was social services involvement. As a result of this study guidance was issued to all new junior psychiatric staff as part of their induction process to make enquiries about children and their welfare.     

Isolation of leptospires and demonstration of antibodies in human leptospirosis in Madras, India

Among 25 clinically suspected cases of leptospirosis, organisms could be isolated from blood and urine of only 10 cases but demonstrated in 15 cases. Antibody titres at a low level were observed to one or more leptospiral antigens in all 25 cases. Nine of the repeated samples from 12 cases showed a four-fold rise in titre. The highest antibody titres were seen against autumnalis. The predominant clinical picture was of fever, myalgia, conjunctival suffusion and jaundice with renal involvement.     

肺曲霉菌病36例外科治疗体会

目的研究肺曲霉菌病的特点,并总结其治疗经验。方法回顾我院外科56例肺曲霉菌病患者的临床资料与随访结果。结果在36例患者中,其中无原发肺疾病的患者有21例,有原发肺疾病的患者有15例。在术前确诊为肺曲霉菌病的患者有15例,21例患者中有8例患者被误诊为肺结核,5例患者被误诊为肺部占位病变,6例患者被误诊为支气管扩张症,1例患者被误诊为肺脓肿,1例患者被误诊为肺囊肿。术后可能伴有的并发症包括气胸、伤口感染、残腔形成肺膨胀不良等症状。全组56例患者无1例死亡,随访记录2～96个月,无1例出现复发或死亡现象。结论肺曲霉菌病利用手术治疗可更好的消除病症,达到预防咯血复发的效果。应根据病情的严重情况选择合适的手术方式,尽量不进行肺叶切除手术。     

Extra pulmonary tuberculosis in children: two years study

Tuberculosis (TB) is an important health problem in developing countries, with varying clinical presentations depending on the organs/systems involved. To study the spectrum of clinical and paraclinical aspects of extra pulmonary TB in children suffering from pulmonary TB. This study has been carried out on 65 children with tuberculosis, admitted in TB wards of National Research Institute of Tuberculosis and Lung Disease (N.R.I.T.L.D) during 2004-2006. All patients were investigated according to specific diagnostic criteria including; history of contact with TB patient, clinical manifestations, radiological findings, tuberculin test and bacteriologic or pathologic results and after confirmation, treatment was administered. Out of 65 cases, 14 had different types of extra pulmonary tuberculosis, and data concerning following factors were studied: age, gender, race, site of involvement, bacteriology, pathology, ADA (ascitic fluid), PCR (tissue specimens), history of close contact, HIV tests (ELISA), tuberculin test, radiological findings, and immunological studies (in disseminated TB). Of 14 cases, 8 were girls and 6 were boys with mean age of 8.75 ± 4.2. Nine patients were Iranian and 5 were Afghan. History of close contact was detected in 4 cases. Type of involvement was: 5 cervical adenitis, 3 osteoarticular disease, 2 peritonitis and 2 disseminated form of tuberculosis, one pericarditis, one renal tuberculosis. Radiological findings showed 4 pulmonary disease and 3 osteoarticular involvement. Tuberculin skin tests greater than 15 mm observed in 5 cases, 9 patients had 0-5 mm induration. 4 cases had concomitant pulmonary and extra pulmonary involvement. Positive AFB in gastric lavage was recognized in 4 cases, in which 3 showed positive cultures for MTB. Pathological examinations in 10 cases revealed granuloma with caseation compatible with tuberculosis, five in lymphadenopathy, three in osteoarticular, two in abdominal tuberculosis. According to this study, 20% of patients had extra pulmonary involvement, which is comparable to other reports (20-25%) and TB lymphadenitis is the most common from of presentation.     

Review of leptospirosis notifications in Queensland and Australia: January 1998-June 1999

The World Health Organization/Food and Agricultural Organization Collaborating Centre for Reference and Research on Leptospirosis, Western Pacific Region, accredited since 1958, is part of Queensland Health Scientific Services, which provide tertiary level support in epidemiology, surveillance, training and diagnosis for hospitals and pathology laboratories across the State. Databases for leptospirosis on a global, Australian and State-wide basis are maintained on site and support public health authorities in Australia, WHO and the International Leptospirosis Society. Queensland data collated and analysed from leptospirosis questionnaires, and a brief overview of Australian data based on questionnaire responses for notified cases from 1998 to June 1999, are summarised. The increase in leptospirosis notifications (77%) during 1998 possibly signalled greater awareness of the disease by clinicians. There was a significant increase in leptospirosis notifications for children and students and a high rate of hospitalisation of cases. An outbreak in North Queensland during the first half of 1999 resulted in 184 notifications with over 50% of cases hospitalised. Polymorphic presentation of the disease with severe pulmonary haemorrhage is associated in particular with the serovar australis. Serovar zanoni continues to be a major cause of severe clinical leptospirosis. Several cases were diagnosed in tourists. One of these cases presented with severe respiratory distress and required 14 days in hospital.     

Multicentre survey of incidence and public health impact of leptospirosis in the Western Pacific

The objectives of the study were to describe the mode of circulation (endemic or epidemic) of human leptospirosis in various Pacific island states and territories by identifying predominant Leptospira serogroups and the most probable routes of human exposure, and to recommend a feasible laboratory strategy for leptospirosis in the Pacific. From September 2003 to December 2005, 263 leptospirosis suspect patients were recruited by public practitioners on 11 Pacific islands, using the WHO case definition. Diagnosis was confirmed using a three-level serology algorithm and a regional laboratory network. Sixty-nine leptospirosis cases were identified from seven islands: Futuna, Raiatea and the Marquesas Islands where outbreaks were apparent, and Vanuatu, Fiji, Palau and Wallis where sporadic cases indicated at least the presence of the disease. Most patients were men aged 17-40 years. The infection appeared to occur during the course of normal daily activities more often than following specific professional exposure. The dominant presumptive serogroups were Icterohaemorrhagiae and Australis, highly suggestive of a rodent reservoir. This study confirms the widespread presence of leptospirosis in the Pacific region. It should help in the implementation of local leptospirosis control plans and highlights the role of on-site laboratory confirmation.     

Clinical diagnosis and geographic distribution of leptospirosis, Thailand

We defined the positive predictive accuracy of a hospital-based clinical diagnosis of leptospirosis in 9 provinces across Thailand. Of 700 suspected cases, 143 (20%) were confirmed by laboratory testing. Accuracy of clinical diagnosis varied from 0% to 50% between the provinces and was highest during the rainy season. Most confirmed cases occurred in the north and northeast regions of the country.     

Leptospirosis in Kolenchery, Kerala, India: Epidemiology, prevalent local serogroups and servoars and a new serovar

Leptospirosis is the most widespread zoonosis in the world. It is mostly an occupational disease especially in rural areas. Kolenchery is in the midlands of Kerala. The landscape consists of marshy land and dry land interspersed by rivulets and ponds. Irrigation of dry lands for cultivation during the summer months started in mid 1980s after the irrigation projects were commissioned. Cases of leptospirosis were rarely diagnosed in Kolenchery before 1987. Since then a yearly increase in incidence is observed. No major study on either epidemiology or clinical picture has been done on human leptospirosis in Kerala so far. The aim of this study was to define the major clinical presentations, epidemiology of the infection and demonstrate the predominant serogroups and serovars causing the illness in this limited geographical area. The study involves 976 cases of leptospirosis confirmed by culture and/or serological tests. Serogroups Autumnalis, Australis and Icterohaemorrhagiae were the commonest. Mortality rate was 5.32%. The increase in incidence is probably due to the geographical characteristics, continuous moisture of the soil due to irrigation in summer and year-round cultivation making food and cover available to host rodents. Close interaction of humans, animals, soil and water in this region make the spread of leptospirosis to humans easy. Confirmation of cases has been done by enzyme linked immunosorbent assay (ELISA) and/or microscopic agglutination test (MAT) and/or by culture. Serovar identification has been done in 21 cultures isolated from patients. One new serovar belonging to serogroup Australis has been identified from a patient and named serovar Australis bharathy.     

云南孟连县钩端螺旋体病发病率调查

在我省南亚热带双季稻种植区总人口78,698人的孟连县进行钩体病调查,一年内检诊患者1,752例,实验室确诊钩体病125例,年发病率158.83/10万,远远超过历史和同类地区的记录。在当地传染病中居第3位。但发病率因地、时性别、年龄而异,坝区高达526.9/10万,半山区97.7/10万,山区60.3/10万;2~12月均可见病例发生,但8月最高(36.0/10万);男性(214.52/10万)显著高于女性(102.36/10万);各年龄组中20~24岁组最高,达435.0/10万。临床表现有4型,流感伤寒占95.2%,其中典型病例只占3.92%,误诊量很大。据此认为以往根据疫情报表中的钩体病数来计算的发病率是极不确切的。     

Spatial epidemiology of suspected clinical leptospirosis in Sri Lanka

Leptospirosis is one of the most widespread zoonoses in the world. A large outbreak of suspected human leptospirosis began in Sri Lanka during 2008. This study investigated spatial variables associated with suspected leptospirosis risk during endemic and outbreak periods. Data were obtained for monthly numbers of reported cases of suspected clinical leptospirosis for 2005-2009 for all of Sri Lanka. Space-time scan statistics were combined with regression modelling to test associations during endemic and outbreak periods. The cross-correlation function was used to test association between rainfall and leptospirosis at four locations. During the endemic period (2005-2007), leptospirosis risk was positively associated with shorter average distance to rivers and with higher percentage of agriculture made up of farms <0·20 hectares. Temporal correlation analysis of suspected leptospirosis cases and rainfall revealed a 2-month lag in rainfall-case association during the baseline period. Outbreak locations in 2008 were characterized by shorter distance to rivers and higher population density. The analysis suggests the possibility of household transmission in densely populated semi-urban villages as a defining characteristic of the outbreak. The role of rainfall in the outbreak remains to be investigated, although analysis here suggests a more complex relationship than simple correlation.