Epidemiology of human leptospirosis in Malaysia, 2004-2012

Leptospirosis is an emerging disease, especially in countries with a tropical climate such as Malaysia. A dramatic increase in the number of cases has been reported over the last decade; however, information on the epidemiological trends of this disease is lacking. The objective of this study is to provide an epidemiological description of human leptospirosis cases over a 9-year period (2004-2012) and disease relationship with meteorological, geographical, and demographical information. A retrospective study was undertaken to describe the patterns of human leptospirosis cases and their association with intrinsic (sex, age, and ethnicity) and extrinsic (location, rainfall, and temperature) factors. Data was grouped according to age, sex, ethnicity, seasonality and geographical distribution, and analyzed using statistical tools to understand the influence of all the different factors on disease incidence. A total of 12,325 cases of leptospirosis were reported between 2004 and 2012 with an upward trend in disease incidence, with the highest in 2012. Three hundred thirty-eight deaths were reported with an overall case fatality rate of 2.74%, with higher incidence in males (9696; 78.7%) compared with female patients (2629; 21.3%), and overall male to female ratio of 3.69:1. Patients aged cohorts between 30-39 years old (16.22 per 100,000 population) had the highest disease incidence while the lowest incidence occurred between <1 to 9 years old (3.44 per 100,000 population). The average incidence was highest amongst Malays (10.97 per 100,000 population), followed by Indians (7.95 per 100,000 population). Stratification according to geographical distribution showed that the state of Malacca had the highest average disease incidence (11.12 per 100,000 population) followed by Pahang (10.08 per 100,000 population). The states of Terengganu, Kelantan, and Perak recorded similar rates of incidence (≈8.00 per 100,000 population), while Johor with the least number of reported cases (1.80 per 100,000 population). Positive relationships were recorded between the number of reported cases with the number of raining days per month and monthly average temperature (p-value<0.05). However, no significant association was noted between rainfall volume and number of reported Leptospirosis cases. This collaborative efforts between medical, academic and governmental institutions has enabled the construction of this comprehensive database that is essential to understand the disease trends in Malaysia and add insights into the prevention and control of this disease.

Human Leptospirosis in Malaysia

The history and epidemiology of human leptospirosis in Malaysia from 1925 to 2012 are described. Previous studies have demonstrated that leptospirosis is an endemic disease in Malaysia occurring in both urban and rural locations. The number of cases has risen dramatically since the Ministry of Health Malaysia highlighted leptospirosis as a notifiable disease in 2010, with reported cases increasing from 248 cases in 2004 to 3604 in 2012. The incidence of infection among the population suggests that occupation, sex, age, ethnic background, water recreational activities, and sporting events are risk factors. A robust surveillance system is now in place to monitor temporal and spatial changes in the incidence and prevalence of infection and to identify risk areas and disease behavior. Despite extensive studies over the past decade, there is a still a need to describe local serovars in host carriers and the human population, with the view to develop an effective vaccine against leptospirosis.