Following the widespread use of poliovirus vaccine in the mid-1950s, the incidence of poliomyelitis declined dramatically in many industrialized countries. A global effort to Eradication of infectious disease polio began in 1988, led by the World Health Organization, UNICEF, and The Rotary Foundation. These efforts have reduced the number of annual diagnosed cases by 99.9 percent; from an estimated 350,000 cases in 1988 to a low of 483 cases in 2001, after which it remained at a level of about 1,000 – 2000 cases per year for a number of years. In 2015, cases decreased to 98 and further decreased in 2016 to 37 wild cases and 5 circulating vaccine-derived cases, but increased in 2017 to 22 wild cases and 91 circulating vaccine-derived cases. Polio is one of only two diseases currently the subject of a global eradication of infectious diseases, the other being Guinea worm disease. So far, the only diseases completely eradicated by humankind are smallpox, declared so, in 1980, and rinderpest, likewise, in 2011. A number of eradication milestones have already been reached, and several regions of the world have been certified polio-free.
How many cases were there in 2015 vs 2016?
61