Why did Ebola epidemic die out so quickly?
Last year, all the world was alarmed by a sudden attack of Ebola epidemic. With its extremely high mortality rate, this uncontrollable virus spread throughout the West Africa, resulting in a few thousand mortality within a few months. WHO declared a war against Ebola, expecting some possibility that this virus might end up threatening the entire global population.
Well, however, how about now? It seems that everybody who once was scared by the news about Ebola from the mass media already forgot what happened last year. In fact, the total number of deaths was a few thousand last year, but it is still a few thousand now at the end of 2015. Center for Disease Control and Prevention (CDC) introduce the case of Ebola as “2014 Ebola Epidemic in West Africa”, making it clear that this is not an present issue.
So what made this once seemingly overwhelming disaster to be forgotten so quickly? Adopting a bit of concepts in general epidemic control theories, we can say that Ebola was the case where we can easily decrease the R0 factor (the average number of people that are infected by one subject until the subjects’ recovery or death) with a little effort of intervention. The key reason why this was possible is actually hidden in the nature of Ebola. Since the virus was so fatal, the death rate was so high that the host died too quickly to infect others. Also, more importantly, the way that the Ebola spreads out is only through the direct contact or the exchange of body fluids, which results in already low p, the probability of infection per contact. This p value was even lower in the developed countries with higher quality of public hygiene and sanitary control, and, thus, the threat of Ebola was restricted only to its first origin, the West Africa. Even, by doing proper quarantine–lowering k, the number of people that each person comes into contact, we were able to see the immediate drop in the rate of spread of the deadly virus. In this sense, the case study of Ebola provides us a real example that shows the importance of effective epidemic intervention.
http://www.cdc.gov/vhf/ebola/outbreaks/2014-west-africa/case-counts.html
http://www.cs.cornell.edu/home/kleinber/networks-book/networks-book-ch21.pdf