title: Human leptospirosis in Portugal: A retrospective study of eighteen years.
abstract: BACKGROUND
  Leptospirosis, an under-recognized public health problem, needs to be confirmed through specific laboratory diagnosis.
  
  
  METHODS
  We describe herein a series of 4618 symptomatic patients for whom a microagglutination test (MAT) serology was available, representing a unique picture of human leptospirosis in central mainland Portugal and the Azores islands of São Miguel and Terceira, over eighteen- and twelve-year periods, respectively.
  
  
  RESULTS
  The distribution of the 1024 (22%) cases identified was an average 57 cases per year, with higher frequency in males (67%). These represent the majority of leptospirosis notifications in Portugal, with a higher annual incidence rate in the islands, compared to the central mainland (11.1 and 1.7/100,000 population, respectively). Middle-aged adults (25-54 years) were most frequently infected (45%). Cases occurred mainly in December and January. Serovars from nine presumptive serogroups caused infection, with a predominance of Icterohaemorrhagiae, Pomona, and Ballum, accounting for 66% of cases.
  
  
  CONCLUSIONS
  Seropositivity was associated with both anicteric and icteric leptospirosis. Several risk factors and a higher transmission risk in certain areas were emphasized. Leptospirosis was confirmed as a steadily increasing public health problem; good surveillance, communication, and laboratory support are thus necessary to reduce the impact of leptospirosis in areas at risk.
authors.affiliation: Unidade de Leptospirose e Borreliose de Lyme, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisboa, Portugal.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Vieira
authors.forename: Maria Jacinta
authors.initials: MJ
authors.lastname: Gama-Simões
authors.forename: Margarida
authors.initials: M
authors.lastname: Collares-Pereira
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001394:Azores / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007922:Leptospirosis / Q000453:epidemiology* / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D009790:Occupations; D011174:Portugal / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D016036:Seroepidemiologic Studies; D015047:Zoonoses / Q000453:epidemiology / Q000382:microbiology