title: Modelling Estimates of Norovirus Disease in Patients with Chronic Medical Conditions.
abstract: BACKGROUND
  The burden of disease due to norovirus infection has been well described in the general United States population, but studies of norovirus occurrence among persons with chronic medical conditions have been limited mostly to the immunocompromised. We assessed the impact of norovirus gastroenteritis on health care utilization in US subjects with a range of chronic medical conditions.
  
  
  METHODS
  We performed a retrospective cohort study using MarketScan data from July 2002 to December 2013, comparing the rates of emergency department visits, outpatient visits and hospitalizations among patients with chronic conditions (renal, cardiovascular, respiratory, immunocompromising, gastrointestinal, hepatic/pancreatic and neurological conditions and diabetes) with those in a healthy population. We estimated the rates of these outcomes due to norovirus gastroenteritis using an indirect modelling approach whereby cases of gastroenteritis of unknown cause and not attributed to a range of other causes were assumed to be due to norovirus.
  
  
  RESULTS
  Hospitalization rates for norovirus gastroenteritis were higher in all of the risk groups analyzed compared with data in otherwise healthy subjects, ranging from 3.2 per 10,000 person-years in persons with chronic respiratory conditions, to 23.1 per 10,000 person-years in persons with chronic renal conditions, compared to 2.1 per 10,000 among persons without chronic conditions. Over 51% of all norovirus hospitalizations occurred in the 37% of the population with some form of chronic medical condition. Outpatient visits for norovirus gastroenteritis were also increased in persons with chronic gastrointestinal or immunocompromising conditions.
  
  
  CONCLUSIONS
  Norovirus gastroenteritis leads to significantly higher rates of healthcare utilization in patients with a chronic medical condition compared to patients without any such condition.
authors.affiliation: P95 Pharmacovigilance and Epidemiology Services, Leuven, Belgium.
authors.forename: Thomas
authors.initials: T
authors.lastname: Verstraeten
authors.affiliation: Takeda Development Center Americas, Inc., Deerfield, Illinois, United States of America.
authors.forename: Baoguo
authors.initials: B
authors.lastname: Jiang
authors.affiliation: Takeda Pharmaceuticals International, Zurich, Switzerland.
authors.forename: John G
authors.initials: JG
authors.lastname: Weil
authors.affiliation: Takeda Development Center Americas, Inc., Deerfield, Illinois, United States of America.
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Lin
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D017250:Caliciviridae Infections / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease / Q000453:epidemiology*; D003695:Delivery of Health Care / Q000706:statistics & numerical data; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005759:Gastroenteritis / Q000175:diagnosis / Q000453:epidemiology / Q000821:virology; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D015233:Models, Statistical; D029322:Norovirus / Q000502:physiology*; D010045:Outpatients / Q000706:statistics & numerical data; D012307:Risk Factors; D012621:Seasons; D055815:Young Adult