title: Design and structure of the Estonian HIV Cohort Study (E-HIV).
abstract: BACKGROUND
  Estonia is experiencing the new Eastern Europe human immunodeficiency virus (HIV) epidemic, with the highest incidence of new infections in the EU. We describe demographic changes, HIV-related laboratory parameters and co-infections during the concentrated HIV epidemic using the Estonian HIV Cohort Study (E-HIV) database, founded in 2009.
  
  
  METHODS
  All 3750 subjects in the E-HIV database on December 31, 2013 were included. Subjects were divided into risk groups: people who inject drugs (PWIDs), sexual transmission (heterosexual/homosexual), and other (perinatal) or unknown risk group. Subjects diagnosed before 2009 (first period) and after (second period) were analyzed separately.
  
  
  RESULTS
  The mean age at diagnosis has increased from 22.8 years (interquartile range (IQR) = 19.5-27.2) to 29.7 years (IQR = 25.3-36.2) (p < 0.001) between the first and second periods. PWIDs were younger than other transmission groups (23.2 vs 27.1; p < 0.001). There is a statistical difference in the route of transmission among genders, with overall increasing sexual transmission. The most common AIDS-defining illness was tuberculosis (0.5%). HIV/hepatitis C (HCV) co-infection was diagnosed in 42% of cases. The population median CD4 + cell count at diagnosis has declined over the years; in total 53% have been late presenters. Half of the patients are receiving antiretroviral treatment (cART). The most common combinations are nucleoside reverse transcriptase inhibitor (NRTI) backbone plus protease inhibitors (PIs) (57%) or NRTI backbone + non-NRTIs (42%).
  
  
  CONCLUSIONS
  The E-HIV enables us to fill the gap in the lack of data on the course of the new Eastern European HIV epidemic. These data demonstrate that the HIV epidemic in Estonia is moving from PWIDs to the general population, suggesting that prevention measures and testing guidelines should be revised.
authors.affiliation: From the Institute of Microbiology, Faculty of Medicine, University of Tartu , Tartu , Estonia.
authors.forename: Pilleriin
authors.initials: P
authors.lastname: Soodla
authors.forename: Heli
authors.initials: H
authors.lastname: Rajasaar
authors.forename: Radko
authors.initials: R
authors.lastname: Avi
authors.forename: Kai
authors.initials: K
authors.lastname: Zilmer
authors.forename: Kersti
authors.initials: K
authors.lastname: Kink
authors.forename: Liilia
authors.initials: L
authors.lastname: Novikova
authors.forename: Kristi
authors.initials: K
authors.lastname: Huik
authors.forename: Matti
authors.initials: M
authors.lastname: Maimets
authors.forename: Irja
authors.initials: I
authors.lastname: Lutsar
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage; D018791:CD4 Lymphocyte Count; D015331:Cohort Studies; D004957:Estonia / Q000453:epidemiology; D005260:Female; D015658:HIV Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology; D006801:Humans; D008297:Male; D055815:Young Adult
chemical_list: D019380:Anti-HIV Agents
keywords: Caucasian; HIV epidemic of Eastern Europe; PWID; co-infection