title: Syndromic recognition of influenza A infection in a low prevalence community setting.
abstract: BACKGROUND
  With epidemics of influenza A virus infection, people and medical professionals are all concerned about symptoms or syndromes that may indicate the infection with influenza A virus.
  
  
  RESULTS
  A prospective study was performed at a community clinic of a metropolitan area. Throat swab was sampled for 3-6 consecutive adult patients with new episode (<3 days) of respiratory tract infection every weekday from Dec. 8, 2005 to Mar. 31, 2006. Demographic data, relevant history, symptoms and signs were recorded. Samples were processed with multiplex real time PCR for 9 common respiratory tract pathogens and by virus culture. Throat swab samples were positive for Influenza A virus with multiplex real time PCR system in 12 of 240 patients. The 12 influenza A positive cases were with more clusters and chills than the other 228. Certain symptoms and syndromes increased the likelihood of influenza A virus infection. The syndrome of high fever plus chills plus cough, better with clustering of cases in household or workplace, is with the highest likelihood (positive likelihood ratio 95; 95% CI 12-750). Absence of both cluster and chills provides moderate evidence against the infection (negative likelihood ratio 0.51; 95% CI 0.29-0.90).
  
  
  CONCLUSIONS
  Syndromic recognition is not diagnostic but is useful for discriminating between influenza A infection and common cold. In addition to relevant travel history, confirmatory molecular test can be applied to subjects with high likelihood when the disease prevalence is low.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Po-Yen
authors.initials: PY
authors.lastname: Huang
authors.forename: Ching-Tai
authors.initials: CT
authors.lastname: Huang
authors.forename: Kuo-Chien
authors.initials: KC
authors.lastname: Tsao
authors.forename: Jung-Jr
authors.initials: JJ
authors.lastname: Ye
authors.forename: Shian-Sen
authors.initials: SS
authors.lastname: Shie
authors.forename: Ming-Yi
authors.initials: MY
authors.lastname: Yang
authors.forename: Hsieh-Shong
authors.initials: HS
authors.lastname: Leu
authors.forename: Ping-Cherng
authors.initials: PC
authors.lastname: Chiang
authors.forename: Yin-Che
authors.initials: YC
authors.lastname: Weng
mesh_terms: D000328:Adult; D019411:Clinical Laboratory Techniques; D003151:Community Health Centers / Q000706:statistics & numerical data*; D003710:Demography; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000502:physiology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D016013:Likelihood Functions; D008297:Male; D015995:Prevalence; D012141:Respiratory Tract Infections / Q000175:diagnosis; D013624:Taiwan / Q000453:epidemiology