Plague: Past, Present, and Future

Recent experience with SARS (severe acute respiratory syndrome) [1] and avian flu shows that the public and political response to threats from new anthropozoonoses can be near-hysteria. This can readily make us forget more classical animal-borne diseases, such as plague (Box 1). Box 1. The Plague The causative bacterium (Yersinia pestis) was discovered by Yersin in 1894 [11] (see also [63]). Case-fatality ratio varies from 30% to 100%, if left untreated. Plague is endemic in many countries in the Americas, Asia, and Africa. More than 90% of cases are currently being reported from Africa. Clinical presentation: After an incubation period of 3–7 days, patients typically experience a sudden onset of fever, chills, headaches, body aches, weakness, vomiting, and nausea. Clinical plague infection manifests itself in three forms, depending on the route of infection: bubonic, septicaemic, and pneumonic. The bubonic form is the most common, resulting from the bite of an infected flea. The pneumonic form initially is directly transmitted from human to human via inhalation of infected respiratory droplets. Treatment: Rapid diagnosis and treatment are essential to reduce the risk of complications and death. Streptomycin, tetracyclines, and sulfonamides are the standard treatment. Gentamicin and fluoroquinolones may represent alternatives when the above antibiotics are not available. Patients with pneumonic plague must be isolated to avoid respiratory transmission. Challenges ahead: Biological diagnosis of plague remains a challenge because most human cases appear in remote areas with scarce laboratory resources. So far, the main confirmation techniques were based on the isolation of Y. pestis (requiring a minimum of 4 days). The recent development of rapid diagnostic tests, now considered a confirmation method in endemic areas, opens new possibilities in terms of surveillance and case management. Three recent international meetings on plague (Box 2) concluded that: (1) it should be re-emphasised that the plague bacillus (Yersinia pestis) still causes several thousand human cases per year [2,3] (Figure 1); (2) locally perceived risks far outstrip the objective risk based purely on the number of cases [2]; (3) climate change might increase the risk of plague outbreaks where plague is currently endemic and new plague areas might arise [2,4]; (4) remarkably little is known about the dynamics of plague in its natural reservoirs and hence about changing risks for humans [5]; and, therefore, (5) plague should be taken much more seriously by the international community than appears to be the case. Figure 1 The Global Distribution of Plague Box 2. Recent International Meetings on Plague A meeting on plague in the present, past, and future was held by the Academy of Science and Letters, Oslo, Norway (http://www.cees.no/oslo-plague-meeting). A workshop focusing on the comparison of the Black Death and modern plague was organised by the Wellcome Trust Centre for the History of Medicine, University College, London (http://www.ucl.ac.uk/histmed/). The World Health Organization convened an expert meeting in Antananarivo, Madagascar updating clinical plague definitions, diagnostic methods, vaccines, and antimicrobial therapy, as well as reservoir and vector control strategies (http://www.who.int/csr/disease/plague/interregionalmeeting2006/en/index.html).