ABSTRACT
Leptospirosis is an emerging infectious disease of global importance, as illustrated by recent large outbreaks on virtually all continents. The disease is caused by pathogenic leptospires and characterized by a broad spectrum of clinical manifestations, varying from unapparent infection to fulminant, life-threatening disease. In its mild form, leptospirosis may present with fever, headache, and myalgias. Severe leptospirosis, characterized by jaundice, renal disorders, and hemorrhagic diathesis, is referred to as Weil’s syndrome. Weil’s syndrome is associated with case fatality rates (CFR) ranging from 5% to 20%. Either concomitant or not, severe pulmonary hemorrhage syndrome (SPHS) is worldwide emerging and, with a CFR exceeding 70%, presents the most severe form of the disease.1 Because of the wide variety of clinical manifestations, mostly uncharacteristic, leptospirosis mimics many other diseases such as in³uenza; hepatitis; dengue; Hantavirus infections and other viral hemorrhagic fevers; yellow fever, malaria, typhoid fever and other enteric diseases; and pneumonia.2-7 Therefore, it is frequently confused with any of these other diseases that often are endemic and epidemic under the same ecological and climatologic conditions. ConŠrmation of clinically suspected leptospirosis cases at the laboratory also has many bottlenecks. Standard tests, such as culturing and the microscopic agglutination test (MAT) are tedious, laborious, and require well-equipped laboratories with experienced staff. Therefore, performance
of these tests is restricted to a few “expert” centers. Novel or adapted simpliŠed diagnostic tests are badly needed. Several rapid tests for human use are currently available.8 Meaningful comparisons to ascertain their relative merits as diagnostic tools are scarce,9-11 and performance appears to vary in distinct regions.12 Therefore, these tests are for screening purposes only, and results must be conŠrmed or locally evaluated by standard tests. In addition, serological tests are applicable only at a later stage of disease when effective treatment with antibiotics is less effective. The lack of awareness is mainly due to the uncharacteristic clinical manifestations and the technically demanding laboratory tests, making the disease difŠcult to diagnose. This makes leptospirosis one of the most overlooked and neglected infectious diseases. Worldwide surveys performed by the International Leptospirosis Society (ILS) revealed that from 300,000 to 500,000 recorded severe leptospirosis cases occurred annually.13,14 Hantavirus infections and dengue are viral hemorrhagic fevers that are frequently confused with leptospirosis6,7,15 and that beneŠt from more attention. Comparison of global numbers of severe cases and CFRs of leptospirosis with those of dengue and Hantavirus infections, shows that leptospirosis is at least equal to both as a public health hazard.15,16 It should be noted that notiŠcation systems are lacking in most high-prevalence countries and that usually only hospitalized cases of Weil’s syndrome are recognized. The unbalanced reporting to ILS by predominantly low-prevalence partners probably caused a
97.1 Introduction ....................................................................................................................................................................1169 97.1.1 ClassiŠcation, Morphology, and Genome Structure ...........................................................................................1170 97.1.2 Clinical Features and Pathogenesis ....................................................................................................................1172 97.1.3 Diagnosis ............................................................................................................................................................1174
