title: Subclinical Plasmodium falciparum infections act as year-round reservoir for malaria in the hypoendemic Chittagong Hill districts of Bangladesh.
abstract: OBJECTIVE
  An analysis of the risk factors and seasonal and spatial distribution of individuals with subclinical malaria in hypoendemic Bangladesh was performed.
  
  
  METHODS
  From 2009 to 2012, active malaria surveillance without regard to symptoms was conducted on a random sample (n=3971) and pregnant women (n=589) during a cohort malaria study in a population of 24000.
  
  
  RESULTS
  The overall subclinical Plasmodium falciparum malaria point prevalence was 1.0% (n=35), but was 3.2% (n=18) for pregnant women. The estimated incidence was 39.9 per 1000 person-years for the overall population. Unlike symptomatic malaria, with a marked seasonal pattern, subclinical infections did not show a seasonal increase during the rainy season. Sixty-nine percent of those with subclinical P. falciparum infections reported symptoms commonly associated with malaria compared to 18% without infection. Males, pregnant women, jhum cultivators, and those living closer to forests and at higher elevations had a higher prevalence of subclinical infection.
  
  
  CONCLUSIONS
  Hypoendemic subclinical malaria infections were associated with a number of household and demographic factors, similar to symptomatic cases. Unlike clinical symptomatic malaria, which is highly seasonal, these actively detected infections were present year-round, made up the vast majority of infections at any given time, and likely acted as reservoirs for continued transmission.
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Kerry L
authors.initials: KL
authors.lastname: Shannon
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Wasif A
authors.initials: WA
authors.lastname: Khan
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Sack
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: M Shafiul
authors.initials: MS
authors.lastname: Alam
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Sabeena
authors.initials: S
authors.lastname: Ahmed
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Chai Shwai
authors.initials: CS
authors.lastname: Prue
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Jacob
authors.initials: J
authors.lastname: Khyang
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Malathi
authors.initials: M
authors.lastname: Ram
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: M Zahirul
authors.initials: MZ
authors.lastname: Haq
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Akter
authors.affiliation: Johns Hopkins Malaria Research Institute, Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615N. Wolfe St, Rm W4612, Baltimore, MD 21205, USA; Department of Geography, University of Florida, Gainesville, Florida, USA.
authors.forename: Gregory E
authors.initials: GE
authors.lastname: Glass
authors.affiliation: Johns Hopkins Malaria Research Institute, Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615N. Wolfe St, Rm W4612, Baltimore, MD 21205, USA.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Shields
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
authors.forename: Sean R
authors.initials: SR
authors.lastname: Galagan
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA; University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Myaing M
authors.initials: MM
authors.lastname: Nyunt
authors.affiliation: Johns Hopkins Malaria Research Institute, Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615N. Wolfe St, Rm W4612, Baltimore, MD 21205, USA. Electronic address: dsulliv7@jhmi.edu.
authors.forename: David J
authors.initials: DJ
authors.lastname: Sullivan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D058345:Asymptomatic Infections / Q000453:epidemiology*; D001459:Bangladesh / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D016778:Malaria, Falciparum / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D015995:Prevalence
keywords: Asymptomatic; Epidemiology; Malaria; Rapid diagnostic test; Subclinical