The Epidemiological Bulletin is published by the Area of Health Surveillance and Disease Prevention and Control (HSD), Pan American Health Organization, Regional Office of the World Health Organization. Address: 525 Twenty-third Street, N.W., Washington, DC. 20037, U.S.A. Telephone: (202) 974.3855. Fax: (202) 974.3674. http://www.paho.org. The texts and the images can be reproduced freely provided that 1) the author/image is cited correctly; 2) the text is accompanied by the credit "Reprinted of the Epidemiological Bulletin of the Pan American Health Organization. Pan American Health Organization, Regional Office of the World Health Organization". 3) A copy of the printed matter is sent to the editor.