The Zika virus is raising fears around the globe, including the continental U.S., leading the World Health Organization (WHO) to declare an international health emergency due to its transmission. The virus is expected to spread from northern Argentina to the southern U.S. by the end of 2016, possibly infecting millions of people.

Zika was discovered almost 70 years ago, but it wasn't linked to outbreaks until 2007. The outbreak began on Yap Island of Micronesia, infecting approximately 75 percent of the population. Six years later, the virus appeared in French Polynesia, along with other outbreaks like dengue and chikungunya, according to the WHO.

There are theories on how the virus made its way to Brazil, including the possibility that it was transmitted at an international canoe event held in Rio de Janeiro in August 2014, which included competitors from various Pacific Islands. Now, in 2016, the virus has spread to throughout several countries, including Argentina, Canada, Chile, France, Italy, New Zealand, Peru, Portugal, and the U.S. during this outbreak. Travel warnings have been issued by governments or health agencies, like the U.K., Ireland, Malaysia, and the EU.

In the U.S., the Centers for Disease Control and Prevention issued a travel warning Monday, advising pregnant women and their partners to not travel to Miami, specifically Wynwood. This is the first time the CDC has warned people to not travel to an American neighborhood for fear of catching an infectious disease.