#12,797
Three days ago in WHO Update: Plague In Madagascar, we looked at what has become pretty much an annual event, a seasonal outbreak of Plague on the island of Madagascar. This year's outbreak, however, is a little bit different from the outbreaks of the past:
- Cases began to appear in August, about a month earlier than usual
- Cases are appearing in a number of densely populated cities, not in the rural highlands as in years past
- And most importantly, a high percentage of cases (60%+) have been of the highly transmissible pneumonic plague, not the easier to control bubonic presentation
All of which makes this year's outbreak in Madagascar a bit of an outlier, although the reasons behind that remain unclear.Whenever a pathogen begins to behave differently, it quickly captures our attention. While we like to think we've got most of these older diseases pegged, in truth, viral and bacterial evolution can quickly upturn everything we think we know.
- Until 2012, the idea that camels could carry and spread a deadly SARS-like virus was unheard of. Our view of coronaviruses, and camels changed overnight with the emergence of MERS.
- Prior to 2013, H7 avian viruses were considered far less of a threat than H5N1. Today, H7N9 is considered to have the greatest pandemic potential of all of the avian viruses in circulation.
- And Ebola, before 2014, was believed incapable of sustained transmission since it only occurred in remote areas deep in central Africa, and it was so virulent it would quickly burn itself out. All that changed when Ebola turned up in West Africa, infecting 30,000 and killing more than 11,000 people over nearly a 2 year period.
Monkeypox and other pox viruses are an increasingly emerging threat, over the past decade we've seen a small avalanche of newly discovered tickborne diseases, and mosquito borne threats like Zika, Chikungunya, and Dengue are increasingly common outside the tropics. Bacterial infections, once susceptible to antibiotics, are quickly learning to evade our last lines of defense.
All of these events were predicted (at least generally) by the late (May 22, 1936 - May 15, 2014) anthropologist and researcher George Armelagos of Emory University in his work The Changing Disease-Scape in the Third Epidemiological Transition, where he posited that since the late 1970's we have entered the age of newly emerging infectious diseases, re-emerging diseases and a rise in antimicrobial resistant pathogens
For a more detailed review of that paper, you may wish to revisit my 2016 blog The Third Epidemiological Transition.While none of this is to suggest that pneumonic plague is about to spin out of control on the island of Madagascar, the big lesson from 2014's Ebola outbreak is that we can't rely on a pathogen's past behavior to predict with absolute certainty what it will do next.
With the evolutionary rate of pathogens, changing environments, and a far more mobile society we always need to be prepared for surprises.Some excerpts from the WHO SitRep #1 follow. Of particular note, the WHO is reexamining their Risk Assessment, based on the unusual aspects of this outbreak. Follow the link to read the full 5-page PDF update.
PLAGUE OUTBREAK
Madagascar Health Emergency(Excerpt)
As of 3 October 2017, a total of 194 cases (suspected, probable and confirmed) with 30 deaths (case fatality rate 15.5%) have been reported from 20 districts in 10 regions. Of these, 124 cases and 21 deaths (case fatality rate 16.9%) had the pneumonic form of the disease. Eight healthcare workers from one health facility in Tamatave have contracted pneumonic plague. Of 29 cases with specimens collected, 19 (66%) have been confirmed by either polymerase chain reaction (PCR) or RDT performed at the Institut Pasteur de Madagascar. On 3 October 2017, 37 new cases including 2 deaths have been reported.
On 29 September 2017, the Malagasy health authorities confirmed pneumonic plague as the cause of death of a Seychelles basketball coach, who was attending the Indian Ocean Basket-ball Club championship from 23 September - 1 October 2017. A South African basketball official also tested positive for plague by PCR test on 3 October 2017. The risks of further spread associated with this tournament are currently being assessed, as all the participants are being monitored.
Plague is endemic in Madagascar, especially in the central highlands, where a seasonal upsurge (predominantly the bubonic form) occurs each year, usually between August and September. There are three forms of plague infection, depending on the route of infection: bubonic, septicaemic and pneumonic (for more information, see the link http://www.who.int/mediacentre/factsheets/fs267/en/).
Current risk assessment
A revision to the risk assessment is currently underway. An initial rapid risk assessment based on the situation as of 19 September 2017, concluded that the overall risk at national level was high due to the high transmissibility of pneumonic plague associated with severe disease and detection of this outbreak more than two weeks after the first case died, during which cases travelled to different parts of the country, including the capital Antananarivo. The overall regional risk is moderate due to frequent flights to neighbouring Indian Ocean islands. The global risk is low.
The risk assessment will be re-evaluated by the three levels of WHO, based on the evolution of the situation and the available information.
As the graphic above states, this is a rapidly changing situation. Since Madagascar's plague `season' is just getting started, this outbreak could conceivably persist for months.
Stay tuned.
