Climatic alterations arising in the north of Perú as a result of the El Niño phenomenon (ENSO) have caused variations in the crop volume, changes in the direction of rivers and probably an increase in the rodent population. In February 1999, in a native community in Jacocha, Huancabamba, Piura's mountains, Perú, an outbreak of bubonic plague appeared with five human cases, one of which lead to death. The diagnosis was confirmed by serology (passive hemaglutination). The presence of antibodies in dogs of localities close to Jacocha has confirmed the circulation of Yersinia pestis in the region. The outbreak was controlled by the local sanitary authorities' prompt action. This episode, after an epidemiological silence for more than four years, showed the necessity of intensifying the plague epidemiological surveillance system in this area.