Jpn. J. Infect. Dis., 65 (2), 105-110, 2012
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Bum Sik Chin1, Yun Tae Chae1, Hee Kyung Choi1, Ji-Hyeon Baek1, Sung Joon Jin1, So Youn Shin1, Sang Hoon Han1, Jun Yong Choi1, Chang Oh Kim1*, Young Goo Song1, Seok Hoon Jeong2, and June Myung Kim1
1Department of Internal Medicine and AIDS Research Institute and 2Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Republic of Korea
(Received September 7, 2011. Accepted November 21, 2011)
*Corresponding author: Mailing address: Department of Internal Medicine, Yonsei University College of Medicine, 250 Seongsanno, Seodaemun-gu, Seoul, Republic of Korea, 120-752. Tel: +82-2-2228-1997, Fax: +82-2-393-6884, E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
SUMMARY: 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.