Warning: fopen(/home/virtual/epih/journal/upload/ip_log/ip_log_2025-04.txt): failed to open stream: Permission denied in /home/virtual/lib/view_data.php on line 95 Warning: fwrite() expects parameter 1 to be resource, boolean given in /home/virtual/lib/view_data.php on line 96
Korea Centers for Disease Control and Prevention, Seoul, Korea.
Copyright © 2010 Korean Society of Epidemiology
This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The authors have no conflict of interest to declare on this study.
This article is available from: http://e-epih.org/