Title of Study

Burden of Disease Study: Leptospirosis in an Urban Setting, Metro Manila


  • Project leaders
    • Dr. Maridel P. Borja
    • Dr. Shin-ichi Yoshida (KU)
  • Co-Leader
    • Dr. Mitsuyasu Yabe (KU)
  • Researchers and Assistants
    • Ms. Elaina Al-Qaseer
    • Ms. Ma. Leonora Angelica Casas
    • Mr. Darwin Cagang
    • Dr. Hisako Nomura (KU)
    • Mr. Joseph Moraves Albior (KU)

General Objective

To determine the burden of disease of Leptospirosis in the Philippines

Specific Objectives

To estimate the seroprevalence of Leptospirosis among Metro Manila residents aged 10-65 years old

To identify important risk factors that predispose urban dwellers to Leptospirosis

To generate data on the clinical spectrum, diagnostic and curative measures

To estimate the economic costs of preventive, diagnostic and curative measures against Leptospirosis

To quantify the burden of disease of Leptospirosis in Metro Manila through the estimation of the disability adjusted life years (DALYs) lost

To determine the knowledge, attitudes and practices of the community concerning the prevention and control of Leptospirosis

To estimate economic impact of lepstospirosis

Burden of Disease Study: Leptospirosis in an Urban Setting,
Metro Manila1
Maridel P. Borja, MSc, MSPH, Ph.D.2

1A Project conducted by the College of Public Health, University of the Philippines Manila
in collaboration with
Kyushu University, Japan International Cooperation Agency, World Health Organization and the Department of Science and Technology (Philippines)
2Principal Investigator and Professor, Department of Epidemiology and Biostatistics,
College of Public Health, University of the Philippines Manila


Background: Leptospirosis is a zoonotic disease that brings about a diverse array of clinical manifestations ranging from sub-clinical to undifferentiated febrile illness to jaundice, renal failure and life-threatening severe pulmonary hemorrhagic syndrome. Despite its capability to cause serious sequelae to a relatively large number of high risk groups, Leptospirosis remains one of the “neglected diseases.” Hence, this study was conducted to estimate the health and economic burden of disease due to Leptospirosis in order to help policy makers determine whether or not it should be considered among the priority public health problems in the Philippines.

Methods: Multiple research methods, both quantitative and qualitative, were employed for data collection. The rapid survey included 413 households randomly selected through a three-stage cluster sampling design from 30 barangays in Metro Manila. It entailed face-to-face interview of mothers, environmental checklist and antibody testing of household members aged 10 – 65 years using Enzyme-linked Immunosorbent Assay (ELISA). Those with negative antibody tests were followed-up after 6 months to determine the incidence of sero-conversion. Cases identified through the household survey or referrals for antibody testing were likewise interviewed. The qualitative methods used were review of existing documents on health statistics, review of medical records of 64 Leptospirosis cases from government and private hospitals, key informant interviews of 13 infectious disease experts and review of the costs of hospitalization, diagnostic and therapeutic management of patients, and median income losses of both the patients and their caregivers.

Results: More than 80% of households surveyed were within 8 meters of an open sewer or a pile of trash. More than two-fifths were within 10 meters of filth-filled stagnant creeks. Of 1,825 eligible household members, only 1,136 (62%) had blood specimens for the sero-prevalence survey. Non-response was higher among males and students who were not home during the visit of field workers.

The overall sero-prevalence of Leptospirosis was 32% (95% CI: 29 – 34%). While sero-positivity is not associated with sex, education and fever episodes within the past year, it seems that it is higher among those aged 30 years or older and among those working in agriculture, fishing, forestry, construction, building cleaning and maintenance and support occupations in health care and administration.

Of the 78 sero-negatives tested so far, 4 had positive results translating to an incidence of 10,655 per 100,000 person- years (95% CI: 2,903–27,282 per 100,000 person-years). The ages of the incident cases ranged from 23-36 years; three were unemployed females who attained a high school level of education. The lone male was working in a sales-related occupation. The annual incidence rates per 100,000 reported by the National Epidemiology Center (NEC) from 2003 – 2008 were much lower. These ranged from 1.18 to 2.65. Even in 2009, despite the post Typhoon Ondoy epidemic, the reported incidence was only 18.62 per 100,000. Local experts believe that approximately 60% of cases are unreported and this is largely due to the fact that those who get to be reported are mostly those who seek care in government health facilities.

Based on the chart review, the duration of hospitalization ranged from 1 - 21days with an average of 7.4 days. The duration of disability as determined from interview of cases, ranged from 4 to 30 days, with an average of 12 days. Disability is defined as the patients’ inability to go back to school or work, or to perform the usual household chores. The clinical features of hospitalized patients included fever (100%), myalgia (64%), gastro-intestinal complaints (53%), conjunctival suffusion (45%), vomiting (44%), oliguria (38%), jaundice (30%), nausea (27%), proteinuria (17%), and anuria (11%). According to the Leptospirosis Burden Epidemiology Group (LERG) convened by the World Health Organization, the important sequelae of Leptospirosis are acute renal injury, acute lung injury or both of these. The local experts believed that 36%, 10% and 3.5% of cases, respectively, progress to develop acute renal injury, acute lung injury or both of these. Meanwhile, they estimated that the case fatality for patients with complications are 10% for acute renal injury, 32.5 % for acute lung injury and 69.5 % when both of these are obtaining. In comparison, from 2006 – 2010, the surveillance system of NEC reported case fatalities ranging from 5.8% to 8.7%.

The economic impact of Leptospirosis was roughly estimated as the sum of the costs of hospital stay, diagnostic procedures, therapeutic management and median income losses due to absence from work of both the patient and the caregiver. The average cost per patient was 104 US$ for hospital room; 66 US$ for diagnostic costs; 175 US$ for therapeutic management; 128 US$ for median income loss. Thus, the total cost per patient is 473 US$.

Conclusions: More than a third of Metro Manila residents aged 10 - 65 years had either been exposed or infected with Leptospirosis in the past. Incidence is likewise very high. The source of infection is apparently poor environmental conditions around their homes that favor the breeding of rodents. The incidence is grossly under-reported as evidenced by the sero-conversion rate that was more than 500-fold higher than the reported incidence during the worst epidemic experienced in the Philippines. Because the disease has serious complications, it could also prove fatal to approximately 7.7% of cases. Further, the cost per patient of Leptospirosis (473 US$) is beyond the reach of many Metro Manilans because the minimum wage per month is only 217 US$.

The health threat posed by Leptospirosis will increase exponentially with the advent of climate change. Hence, government should put the infrastructure in place that will ensure flood control and environmental sanitation since these will help stymie not only the problem of Leptospirosis but other public health problems as well.

Keywords: Leptospirosis, Burden of Disease, prevalence, incidence, case fatality, economic impact