It still occurs fairly regularly, even in the USA. We simply have effective treatments now (Yersinia pestis is susceptible to a number of common antibiotics).

From UptoDate (sorry, may violate the 20 year rule with some of this information): "From 2000 to 2009, a total of 21,725 cases of plague with 1612 deaths (7.4 percent fatality rate) were reported worldwide from 16 countries [4]. Since 2000, more than 95 percent of reported cases have been from Africa [4,5]. Outbreaks of human plague, with numbers of cases ranging from 100 to more than 1000, have occurred since 1992 in Zaire, Peru, India, and the Congo [3,4]. Plague reappeared in Malawi, Mozambique, and India in 1994, in Algeria in 2003, and in Libya in 2009, raising concern that the disease may reemerge as a significant worldwide public health hazard [6-10]. An increase in bubonic cases was noted in Uganda in 2006, and more than 1000 cases were recognized in the Congo from 2005 to 2010 related in part to ongoing civil war and strife and focal outbreaks in diamond workers [4,11,12]. These incidence data may be underestimates because diagnostic facilities and surveillance systems are inadequate in many areas of the world where plague is endemic or occurs in focal outbreaks.

In the United States, plague is endemic in all of the western states and has extended north and east over the years. The rate of plague in the United States is low, probably because the affected areas are rural and largely uninhabited. A total of 57 cases of human plague were reported in the United States from 2000 to 2009 [4]. The vast majority of human cases in the United States have occurred in five states: Arizona, California, Colorado, New Mexico, and Texas. Human disease has also been reported from Oklahoma and Oregon [13,14]. In addition, animal and/or flea plague has been identified in western North Dakota and Nebraska"

References from the above:

Perry RD, Fetherston JD. Yersinia pestis--etiologic agent of plague. Clin Microbiol Rev 1997; 10:35.Butler T. Plague gives surprises in the first decade of the 21st century in the United States and worldwide. Am J Trop Med Hyg 2013; 89:788.Human plague in 2000 and 2001. Wkly Epidemiol Rec 2003; 78:130.Butler T. Yersinia infections: centennial of the discovery of the plague bacillus. Clin Infect Dis 1994; 19:655.Campbell GL, Hughes JM. Plague in India: a new warning from an old nemesis. Ann Intern Med 1995; 122:151.Human plague in 1994. Wkly Epidemiol Rec 1996; 71:165.Bertherat E, Bekhoucha S, Chougrani S, et al. Plague reappearance in Algeria after 50 years, 2003. Emerg Infect Dis 2007; 13:1459.Cabanel N, Leclercq A, Chenal-Francisque V, et al. Plague outbreak in Libya, 2009, unrelated to plague in Algeria. Emerg Infect Dis 2013; 19:230.Centers for Disease Control and Prevention (CDC). Bubonic and pneumonic plague - Uganda, 2006. MMWR Morb Mortal Wkly Rep 2009; 58:778.Bertherat E, Thullier P, Shako JC, et al. Lessons learned about pneumonic plague diagnosis from two outbreaks, Democratic Republic of the Congo. Emerg Infect Dis 2011; 17:778.Centers for Disease Control and Prevention (CDC). Human plague--United States, 1993-1994. MMWR Morb Mortal Wkly Rep 1994; 43:242.Centers for Disease Control and Prevention (CDC). Notes from the field: two cases of human plague--Oregon, 2010. MMWR Morb Mortal Wkly Rep 2011; 60:214.

The Yersina Pestis has had subsequent outbreaks since then.

The last global outbreak occurred between 1892-1901- with smaller outbreak reoccurring in some areas over the next decade. This is outbreak is usually referred to as the Third Pandemic. It originated in China and spread from the colonial trading posts in Hong Kong and Shanghai down to Indochina and India and from there out and into the overseas posts of the British and French Empires- eventually being carried across the Pacific to Honolulu, San Francisco, down to Sydney/Melbourne, over to Porto, Portugal, Cape Town, etc. Ultimately this outbreak will touch each of the inhabited continents.

The epidemic spread thanks to fleas who stowed away on shipboard rats and sacks of grain. Migratory animals/people likely brought to disease down from its highland reservoirs- but then it was the global lines of colonial commerce that carried it across the oceans.

I'm not surprised you- or many other people haven't heard of this outbreak, despite its global nature. The mortality rates were significantly lower than they were in the high middle ages or early modern period in Europe. There was also a strong racial element to this outbreak- in European colonial cities like Nouméa, Sydney, Bombay, or Cape Town there was a great deal of blame placed on non-whites for the spread of the disease- and a faith that the disease would in fact respect racial boundaries- striking down only those poor non-whites who lived in squalor and filth. In Honolulu- this plays out in the form of a great fire that burns down Chinatown, most of which had been constructed out of wood at that point.

Despite the blame on non-whites, there was a fear that the disease could spread among whites as well. It did in fact- my own research on this topic shows though that the fatality/dead rates were vastly different between racial groups among those who were 'officially' announced to be infected with the plague. I use quotation marks because often people did everything they could to hide their infection, which no doubt helped it spread. So the unofficial survival rates might be much higher. Generally whites had access to a healthier urban environment and much better medical care- non-whites could often simply be banished to a quarantine with far less individual care or attention. Whites were also under far less surveillance; in the Pacific context, which I am far more familiar with, surveillance of non-white neighborhoods or worker-barracks was far heavier. Any sign of disease and the person would be quarantined along with any family- and then their home often burned to the ground; whereas a respectable white citizen could hide their illness and have their property 'sanitized' without being burned down.

During the outbreak there were attempts to develop a scrum/antidote/immunization. These attempts were at least partly successful- by 1899 and throughout 1900 the Pasteur Institute was able to deploy a serum that gave at least partial immunity to the outbreak. It was not a perfect solution though- according to their trials it only cured the plague outbreak if administered quickly after initial infection and the immunization effects only seemed to last three or four months, so it had to be reapplied frequently. The only problem with widespread application of the serum was the laboratory needs of creating it- so distant colonies and cities lacked the appropriate facilities and expertise to produce the serum. The serum also seemed to lose effectiveness when they tried shipping it over long distances. So ultimately, only cities with Pasteur Institutes in them- or nearby appropriate facilities (like Porto) received the serum in their efforts to combat the outbreak.

Generally speaking the outbreak is remembered in local stories and histories and not connected as a global event- the Honolulu Chinatown fire is a great example of this.

If you want to read some more about this particular outbreak I would recommend:

• Echenberg, Myron. “Pestus Redux: The Initial Years of the Third Bubonic Plague Pandemic, 1894-1901.” Journal of World History 13, no. 2 (Fall 2002): 429-449

• ——. Plague Ports: The Global Urban Impact of Bubonic Plague, 1894-1901. New York: New York University Press, 2007.

I also have some articles coming out about this outbreak- particularly the Pacific context, however, they won't be out in print for a little while still- in fact this is a kind of a reminder than I need to finish my edits and get them back to the editors!