Epidemiological characteristics of an urban plague epidemic in Madagascar, August–November, 2017: an outbreak report

Abstract

Summary Background Madagascar accounts for 75% of global plague cases reported to WHO, with an annual incidence of 200–700 suspected cases (mainly bubonic plague). In 2017, a pneumonic plague epidemic of unusual size occurred. The extent of this epidemic provides a unique opportunity to better understand the epidemiology of pneumonic plagues, particularly in urban settings. Methods Clinically suspected plague cases were notified to the Central Laboratory for Plague at Institut Pasteur de Madagascar (Antananarivo, Madagascar), where biological samples were tested. Based on cases recorded between Aug 1, and Nov 26, 2017, we assessed the epidemiological characteristics of this epidemic. Cases were classified as suspected, probable, or confirmed based on the results of three types of diagnostic tests (rapid diagnostic test, molecular methods, and culture) according to 2006 WHO recommendations. Findings 2414 clinically suspected plague cases were reported, including 1878 (78%) pneumonic plague cases, 395 (16%) bubonic plague cases, one (<1%) septicaemic case, and 140 (6%) cases with unspecified clinical form. 386 (21%) of 1878 notified pneumonic plague cases were probable and 32 (2%) were confirmed. 73 (18%) of 395 notified bubonic plague cases were probable and 66 (17%) were confirmed. The case fatality ratio was higher among confirmed cases (eight [25%] of 32 cases) than probable (27 [8%] of 360 cases) or suspected pneumonic plague cases (74 [5%] of 1358 cases) and a similar trend was seen for bubonic plague cases (16 [24%] of 66 confirmed cases, four [6%] of 68 probable cases, and six [2%] of 243 suspected cases). 351 (84%) of 418 confirmed or probable pneumonic plague cases were concentrated in Antananarivo, the capital city, and Toamasina, the main seaport. All 50 isolated Yersinia pestis strains were susceptible to the tested antibiotics. Interpretation This predominantly urban plague epidemic was characterised by a large number of notifications in two major urban areas and an unusually high proportion of pneumonic forms, with only 23% having one or more positive laboratory tests. Lessons about clinical and biological diagnosis, case definition, surveillance, and the logistical management of the response identified in this epidemic are crucial to improve the response to future plague outbreaks. Funding US Agency for International Development, WHO, Institut Pasteur, US Department of Health and Human Services, Laboratoire d'Excellence Integrative Biology of Emerging Infectious Diseases, Models of Infectious Disease Agent Study of the National Institute of General Medical Sciences, AXA Research Fund, and the INCEPTION programme.

Key Strategies to Address Emerging and Reemerging Infectious Diseases: A Systematic Analysis

“…A truly comprehensive EID response system requires system-wide coordination, ongoing surveillance systems throughout the world, strengthening healthcare resources (personnel, medications, facilities, etc. ), social, behavior, and change interventions, and the integration of appropriate diagnostics into prevention and control plans [14,15,18]. Ten different results (33.3%) stressed the importance of tailored EID surveillance strategy that would prevent and mitigate EID outbreaks [11,12,13,14,15,16,17,18,19,20,21].…”

Performance of plague rapid diagnostic test compared to bacteriology: a retrospective analysis of the data collected in Madagascar

“…If results from this test are inconclusive, a conventional PCR targeting pla, caf1, and inv genes is performed. The new decision tree has been reported along with all details concerning findings during the epidemic [3]. Comparisons between RDT and bacteriological culture may be skewed by factors which could affect the isolation of Y. pestis.…”

“…Indeed, in 2017, Madagascar faced a pneumonic plague (PP) epidemic in two urban areas. A new molecular biology-based diagnostic test was implemented at the CLP and adapted to the epidemic context of PP [3,4].…”

A Survey of Antimicrobial Resistance Determinants in Category A Select Agents, Exempt Strains, and Near-Neighbor Species

“…MDR Yersinia pestis strains isolated in Madagascar in the 1990s harbored plasmids with up to eight AMR determinants, at least four of which confer resistance to recommended therapeutics or prophylactic treatments [13][14][15][16][17]. Fortunately, the strains responsible for more recent outbreaks in Madagascar, the Democratic Republic of Congo, and Uganda do not carry these plasmids and are susceptible to the standard therapeutics [18,19]. Even so, AMR determinants present on mobile elements have the potential to spread widely; a number of reports have described the means of transferring naturally occurring plasmids harboring AMR determinants to and from these strains [14,20,21].…”