Plague Outbreak in Libya, 2009, Unrelated to Plague in Algeria

Nicolas Cabanel, Alexandre Leclercq, Viviane Chenal-Francisque, Badereddin Annajar, Minoarisoa Rajerison, Souad Bekkhoucha, Eric Bertherat, and Elisabeth Carniel

Author affiliations: Author affiliations: Institut Pasteur, Paris, France (N. Cabanel, A. Leclercq, V. Chenal-Francisque, E. Carniel); National Center for Disease Control, Tripoli, Libya (B. Annajar); Institut Pasteur, Antananarivo, Madagascar (M. Rajerison); University Hospital, Oran, Algeria (S. Bekkhoucha); World Health Organization, Geneva, Switzerland (E. Bertherat)

Abstract

After 25 years of no cases of plague, this disease recurred near Tobruk, Libya, in 2009. An epidemiologic investigation identified 5 confirmed cases. We determined ribotypes, Not1 restriction profiles, and IS100 and IS1541 hybridization patterns of strains isolated during this outbreak. We also analyzed strains isolated during the 2003 plague epidemic in Algeria to determine whether there were epidemiologic links between the 2 events. Our results demonstrate unambiguously that neighboring but independent plague foci coexist in Algeria and Libya. They also indicate that these outbreaks were most likely caused by reactivation of organisms in local or regional foci believed to be dormant (Libya) or extinct (Algeria) for decades, rather than by recent importation of Yersinia pestis from distant foci. Environmental factors favorable for plague reemergence might exist in this area and lead to reactivation of organisms in other ancient foci.

Plague is a zoonosis caused by the bacillus Yersinia pestis. Rodents are the reservoir and fleas are the vector of this organism. Humans most often become infected by an infectious fleabite, which leads to development of a bubonic form of plague (1). If the bacillus reaches the lungs, the patient will expel the bacteria while coughing, causing another clinical form: pneumonic plague, which is directly transmissible from person to person. Without prompt and efficient treatment, the case-fatality rate is 40%–70% for bubonic plague and ≈100% for pneumonic plague (1).
The plague bacillus is believed to have originated <20 a="" ago="" asia="" central="" href="http://wwwnc.cdc.gov/eid/article/19/2/12-1031_article.htm?s_cid=eid-gDev-email#r2" in="" title="2" years="">2
), from which it has spread on multiple occasions and caused 3 well-documented pandemics (1). The first pandemic, known as Justinian’s plague, reached Africa and then Europe during the sixth century. The second pandemic struck the countries surrounding the Mediterranean in 1348 and then spread rapidly throughout Europe. The third pandemic started in Hong Kong in 1894 and reached previously unscathed territories worldwide. These 3 pandemics were extremely devastating and killed millions of persons. Because of identification of the causative agent (3), the reservoir, and the vector of the disease at the end of the 19th century (4) and then the availability of effective antimicrobial drugs, human illness and death caused by plague have been considerably reduced since the middle of the 20th century.