title: Viral shedding of 2009 pandemic H1N1 and evaluation of quarantine recommendations.
abstract: Public health authorities recommend that isolation precautions for influenza  should be continued for 7 days after illness onset or until 24 h after the resolution of symptoms,  whichever event lasts longer. However, little data are available regarding the duration of  isolation for patients with 2009 pandemic H1N1 (pH1N1). We recruited patients with confirmed pH1N1  virus infection at a 2,000-bed tertiary care center. Influenza viral loads from oropharyngeal swab  specimens were serially determined by reverse transcriptase quantitative polymerase chain reaction  every other day, and the risk factors for prolonged viral shedding were investigated. To evaluate  the current recommendations for isolation precautions, we measured the intervals between symptom  onset and the last viral RNA detection, and that between the last viral RNA detection and the  point at which the patient was symptom-free for 24 h. From November 2009 to January 2010, 26  patients were enrolled, and viral RNA was detected in more than half of the eligible patients (10  of 19, 52.6%) for ≥7 days after symptom onset. While evaluating the policy for lifting quarantine,  we found that viral RNA was detected in 4 of 15 patients (26.7%) beyond the recommended duration  of isolation. In conclusion, viral RNA was detected in a substantial proportion of hospitalized  patients even when they fulfilled the recommended conditions for lifting quarantine, and we  believe that more prudence is required in this aspect.
authors.affiliation: Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Bum Sik
authors.initials: BS
authors.lastname: Chin
authors.forename: Yun Tae
authors.initials: YT
authors.lastname: Chae
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Choi
authors.forename: Ji-Hyeon
authors.initials: JH
authors.lastname: Baek
authors.forename: Sung Joon
authors.initials: SJ
authors.lastname: Jin
authors.forename: So Youn
authors.initials: SY
authors.lastname: Shin
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Han
authors.forename: Jun Yong
authors.initials: JY
authors.lastname: Choi
authors.forename: Chang Oh
authors.initials: CO
authors.lastname: Kim
authors.forename: Young Goo
authors.initials: YG
authors.lastname: Song
authors.forename: Seok Hoon
authors.initials: SH
authors.lastname: Jeong
authors.forename: June Myung
authors.initials: JM
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000473:pathology / Q000821:virology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009960:Oropharynx / Q000821:virology; D011790:Quarantine / Q000379:methods*; D060888:Real-Time Polymerase Chain Reaction; D013997:Time Factors; D019562:Viral Load; D017201:Virus Shedding