Second meeting of the Leptospirosis Burden Epidemiology Reference Group, Geneva, 22-23 September 2010

The second meeting of the Leptospirosis Burden Epidemiology Reference Group (LERG) was held on 22–23 September 2010 in Geneva. The objectives of this meeting were to:

  • Review and appraise the revised systematic epidemiological review for mortality, morbidity and disability of human leptospirosis;
  • Review draft transmission disease model for leptospirosis and provide technical input for the further development and refinement of the model;
  • Assemble preliminary burden estimates;
  • Identify present knowledge and research gaps; and
  • Advise WHO on next steps for human leptospirosis burden estimation and their translation into policy.

Human leptospirosis is a neglected disease, mostly affecting vulnerable populations in rural settings and semi-urban slums. A systematic literature review estimated the median global annual incidence of endemic human leptospirosis, i.e. excluding outbreaks, as 5 cases per 100 000 population. It is highly probable that this is a gross underestimate, since many cases of leptospirosis are undiagnosed or misdiagnosed, because of lack of awareness of the disease and difficulties in carrying out laboratory confirmation tests. Studies have shown that leptospirosis may represent up to 20% of febrile illness of unknown origin. Limited studies have suggested that the highest median annual incidence occurs in the African Region (95.5 per 100 000 population) followed by the Western Pacific (66.4), the Americas (12.5), South-East Asia (4.8) and Europe (0.5). In some areas, incidence is as high as 975 cases per 100 000. An estimated 17% of hospitalized patients suffer acute lung injury, of which 25% die as a result. Existing data on leptospirosis incidence and disease sequelae are limited, but suggest that Africa, the Western Pacific, and the Americas have the greatest burden of disease, and that fewer economic resources are associated with a higher burden of disease.

An improved understanding of the risk factors and drivers for leptospirosis transmission and infection is needed to devise improved integrated interventions for reduction of sources of infection. Work has started to develop a transmission model, to aid the translation of the burden of disease estimates into contextualized support for decision-making by policy-makers.