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A cluster of lung injury cases associated with home humidifier use: an epidemiological investigation
  1. Hwa Jung Kim1,
  2. Moo-Song Lee1,2,
  3. Sang-Bum Hong3,
  4. Jin Won Huh3,
  5. Kyung-Hyun Do4,
  6. Se Jin Jang5,
  7. Chae-Man Lim3,
  8. Eun Jin Chae4,
  9. Hanyi Lee6,
  10. Miran Jung7,
  11. Young-Joon Park8,
  12. Ji-Hyuk Park9,
  13. Geun-Yong Kwon9,
  14. Jin Gwack9,
  15. Seung-Ki Youn9,
  16. Jun-Wook Kwon10,
  17. Byung-Guk Yang11,
  18. Byung-Yool Jun12,
  19. Yangho Kim13,
  20. Hae-Kwan Cheong14,
  21. Byung Chul Chun15,
  22. Heon Kim16,
  23. Kyuhong Lee17,
  24. Younsuck Koh3
  1. 1Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
  2. 2Department of Preventive Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
  3. 3Department of Pulmonary Medicine and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
  4. 4Department of Radiology, Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
  5. 5Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
  6. 6Department of Nursing, Hanyang University, Seoul, Korea
  7. 7Department of Nursing, Asan Medical Center, Seoul, Korea
  8. 8Division of Vaccine-preventable Diseases Control and National Immunization Program, Korea Centers for Disease Control and Prevention, Osong, Korea
  9. 9Division of Epidemic Intelligence Service, Korea Centers for Disease Control and Prevention, Osong, Korea
  10. 10Center for Infectious Disease Control, Korea Centers for Disease Control and Prevention, Osong, Korea
  11. 11Bureau of Public Health Policy, Ministry of Health and Welfare, Seoul, Korea
  12. 12Korea Centers for Disease Control and Prevention, Osong, Korea
  13. 13Department of Occupational and Environmental Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea
  14. 14Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, Suwon, Korea
  15. 15Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea
  16. 16Department of Preventive Medicine and Medical Research Institute, College of Medicine, Chungbuk National University, Cheongju, Korea
  17. 17Inhalation Toxicology Center, Korea Institute of Toxicology, Jeongeup, Korea
  1. Correspondence to Moo-Song Lee, Department of Clinical Epidemiology and Biostatistics, Department of Preventive Medicine, Asan Medical Center, University of Ulsan College of Medicine, 43-gil Olympic-ro, Songpa-gu, Seoul 138-736, Korea; lee.moosong.md{at}gmail.com, leems{at}amc.seoul.kr

Abstract

Background In April 2011 a tertiary hospital in Seoul, Korea reported several cases of severe respiratory distress of unknown origin in young adults.

Methods To find the route of transmission, causative agent and patient risk factors of the outbreak, an investigation of the epidemic was initiated. Clinicopathological conferences led to the suspicion that the cases related to an inhalation injury. An age- and sex-matched case–control study was therefore performed to examine the inhalation exposure of the patients to various agents.

Results Of the 28 confirmed cases, 18 agreed to participate. A total of 121 age- and sex-matched controls with pulmonary, allergic or obstetric disease were selected. All patients and controls completed questionnaires with questions about exposure to various inhalants. The crude ORs for patient exposure to indoor mould, humidifier use, humidifier detergent use and insecticide use were 4.4 (95% CI 1.5 to 13.1), 13.7 (95% CI 1.8 to 106.3), 47.3 (95% CI 6.1 to 369.7) and 3.9 (95% CI 1.3 to 11.7), respectively. However, when considered concurrently, indoor mould and insecticide use lost statistical significance. Moreover, humidifier use was ruled out as the cause because of a lack of biological plausibility and the weak strength of the association. This suggested that humidifier disinfectant was the cause of the outbreak. This information led the Korean government to order the removal of humidifier detergents from the market. In the years following the ban, no additional cases were detected.

Conclusions Epidemiological evidence strongly suggests that the lung injury outbreak was caused by humidifier detergent use at home.

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