title: Burden of Influenza and Respiratory Syncytial Virus Infection in Pregnant Women and Infants Under 6 Months in Mongolia: A Prospective Cohort Study.
abstract: BACKGROUND
  Pregnant women and infants under 6 months are at risk of influenza-related complications. Limited information exists on their community burden of respiratory viruses.
  
  
  RESULTS
  This prospective, observational open cohort study was conducted in Baganuur district, Ulaanbaatar, Mongolia during 2013/14 and 2014/15 influenza seasons. Influenza-like illness (ILI) and severe acute respiratory infection (sARI) were identified by follow-up calls twice a week. For those identified, influenza and respiratory syncytical virus (RSV) were tested by point-of-care test kits. We calculated overall and stratified (by trimester or age group) incidence rates (IR) and used Cox proportional hazard regression for risk factor analyses. Among 1260 unvaccinated pregnant women enrolled, overall IRs for ILI, sARI and influenza A were 11.8 (95% confidence interval (C.I):11.2-12.4), 0.1 (95%C.I:0.0-0.4), and 1.7 (95%C.I:1.5-1.9) per 1,000person-days, respectively. One sARI case was influenza A positive. IRs and adjusted hazard ratios (Adj.HR) for ILI and influenza A were lowest in the third trimester. Those with co-morbidity were 1.4 times more likely to develop ILI [Adj.HR:1.4 (95%C.I:1.1-1.9)]. Among 1304 infants enrolled, overall ILI and sARI IRs were 15.2 (95%C.I:14.5-15.8) and 20.5 (95%C.I:19.7-21.3) per 1,000person-days, respectively. From the tested ILI (77.6%) and sARI (30.6%) cases, the overall positivity rates were 6.3% (influenza A), 1.1% (influenza B) and 9.3% (RSV). Positivity rates of influenza A and RSV tend to increase with age. sARI cases were 1.4 times more likely to be male [Adj.HR:1.4 (95%C.I:1.1-1.8)]. Among all influenza A and RSV positive infants, 11.8% and 68.0% were respectively identified among sARI hospitalized cases.
  
  
  CONCLUSIONS
  We observed low overall influenza A burden in both groups, though underestimation was likely due to point-of-care tests used. For infants, RSV burden was more significant than influenza A. These findings would be useful for establishing control strategies for both viruses in Mongolia.
authors: Department of Virology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors: Liling
authors: L
authors: Chaw
authors: Department of Virology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors: Taro
authors: T
authors: Kamigaki
authors: National Influenza Center, National Center of Communicable Diseases, Ulaanbaatar, Mongolia.
authors: Alexanderyn
authors: A
authors: Burmaa
authors: National Influenza Center, National Center of Communicable Diseases, Ulaanbaatar, Mongolia.
authors: Chuluunbatiin
authors: C
authors: Urtnasan
authors: Baganuur District, Ulaanbaatar, Mongolia.
authors: Ishiin
authors: I
authors: Od
authors: National Influenza Center, National Center of Communicable Diseases, Ulaanbaatar, Mongolia.
authors: Gunregjaviin
authors: G
authors: Nyamaa
authors: National Influenza Center, National Center of Communicable Diseases, Ulaanbaatar, Mongolia.|Mongolian Academy of Medical Sciences, Ulaanbaatar, Mongolia.
authors: Pagbajabyn
authors: P
authors: Nymadawa
authors: Department of Virology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors: Hitoshi
authors: H
authors: Oshitani
mesh_terms: D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D009980:Influenza A virus / Q000502:physiology; D009981:Influenza B virus / Q000502:physiology; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008986:Mongolia / Q000453:epidemiology; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology*; D011446:Prospective Studies; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology*; D012307:Risk Factors