Hospital-based influenza surveillance in Korea: Hospital-based influenza morbidity and mortality study group

Joon Young Song, Hee Jin Cheong, Sung Hyuk Choi, Ji Hyeon Baek, Seung Baik Han, Seong Heon Wie, Byung Hak So, Hyo Youl Kim, Young Keun Kim, Won Suk Choi, Sung Woo Moon, Jacob Lee, Gu Hyun Kang, Hye Won Jeong, Jung Soo Park, Woo Joo Kim

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24 Citations (Scopus)


Influenza epidemics occur annually with variations in size and severity. Hospital-based Influenza Morbidity & Mortality was established to monitor influenza epidemics and their severity, which is composed of two surveillance systems: emergency room-based and inpatient-based surveillance. Regarding emergency room-based surveillance, influenza-like illness index (influenza-like illness cases per 1,000 emergency room-visiting subjects), number of laboratory-confirmed cases and the distribution of influenza types were estimated weekly. Inpatient-based surveillance included monitoring for hospitalization, complications, and mortality. The emergency room influenza-like illness index correlated well with the number of laboratory-confirmed influenza cases, and showed a bimodal peak at Week 4 (179.2/1,000 emergency room visits) and Weeks 13-14 (169.6/1,000 emergency room visits) of 2012. Influenza A was the predominant strain during the first epidemic peak, while influenza B was isolated exclusively during the second peak. In 2011-2012 season, the mean admission rate of emergency room-visiting patients with influenza-like illness was 16.3% without any increase over the epidemic period. Among the hospitalized patients with influenza, 33.6% (41 out of 122 patients) were accompanied by complications, and pneumonia (28.7%, 35 out of 122 patients) was the most common. Most fatal cases were caused by influenza A (96.2%) after the first epidemic peak. In conclusion, Hospital-based Influenza Morbidity & Mortality was effective for monitoring the trends in circulating influenza activity concurrently with its severity. In the 2011-2012 season, the influenza epidemic persisted for a ≥5-month period, with a bimodal peak of influenza A and B in sequence. Overall, influenza A was more severe than influenza B. J. Med. Virol. 85:910-917, 2013.

Original languageEnglish
Pages (from-to)910-917
Number of pages8
JournalJournal of Medical Virology
Issue number5
Publication statusPublished - 2013 May
Externally publishedYes


  • Influenza
  • Influenza-like illness
  • Surveillance

ASJC Scopus subject areas

  • Infectious Diseases
  • Virology


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