http://news.yahoo.com/ebola-hit-liberia-cancels-nationwide-election-135505061.html
How long did it take Liberia to institute martial law because of the ebola epidemic? 7 Months.
As of 29 September 2014, there were 3458 cases reported, 1830 total deaths, and 914 lab confirmed cases.[11] For comparison, Lassa fever is estimated to kill about 5000 people a year in West Africa,[12] and in Western countries, medical mistakes kill between 44,000 to 400,000 people a year.
Forgot to source the above information. http://en.wikipedia.org/wiki/2014_Ebola_virus_epidemic_in_Liberia
3458 cases out of 4.3 million people, equals to about .08% of the population.
If the US were to use this model, 254,227 people would have to become infected before martial law would be considered. Personally, I think it won't even be 10% of that before that happens. It seems too many Americans can't do math, and 25,000 people is a much scarier number than .008%.
While it certainly is a very deadly and scary disease, so far I don't think it has reached epidemic, nor even pandemic levels yet, but that won't stop the media from reporting it as a biological catastrophe.