About 50% of the world's population lives under the threat of dengue, which is responsible for approximately 390 million infections globally per year.
As of March 2017, there were 84 countries and territories in the world with continuing mosquito-borne transmission of Zika.
Norovirus is the most common viral cause of acute gastroenteritis worldwide, responsible for greater than 90% of epidemic non-bacterial outbreaks of gastroenteritis.
As of April 2017, polio remains endemic to only three countries (Afghanistan, Nigeria, and Pakistan), with 80% of the world now living in certified
Before 1970, only nine countries had experienced severe dengue epidemics. The disease is now endemic in more than 100 countries.
As of March 2017, a decline in cases of Zika infection has been reported in some countries, or in some parts of countries; WHO advises that vigilance needs to remain high.
Norovirus is estimated to cause more than 699 million illness cases each year.
Polio cases have decreased by over 99% since 1988, from an estimated 350,000 cases, to only 37 cases in 2016.