The World Health Organization (WHO) has warned North and South American countries about the spread of the Zika virus across the continent, per the Pan American Health Organization. As of Jan. 23, 2016, reported cases of the mosquito-borne virus has been documented in 21 countries and territories in the Americas.

WHO noted that there is still no vaccine for the Virus spread by Aedes aegypti mosquito with the most effective form of prevention is reducing its populations. It can be done by destroying the insect's habitats while people could prevent bites by using insect repellents and physical barriers.

The countries and territories that already reported cases of the virus include Barbados, Bolivia, Brazil, Cape Verde, Cape Verde, Colombia, Ecuador, El Salvador, French Guiana, Guatemala, Guadeloupe, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Samoa, Suriname and Venezuela. According to PAHO, countries that don't have the Aedes aegypti mosquito like Canada and Chile are less likely to have Zika outbreaks.

In a report by Voice of America, the Zika virus was first discovered in monkeys back in 1947 in Uganda. Cases of the virus were very rare until 2007 when the first serious outbreak happened in 2007. It hit the Pacific island of Micronesia with cases reaching the Cook Islands, Easter Island, New Caledonia and Polynesia.

The Zika virus has also been linked with a rare birth defect called microcephaly, wherein a newborn baby's brain fails to develop properly, resulting to a deformed, small head. The Brazilian Health Ministry has told FOX News that the country has over 3,500 cases of microcephaly causing the government to fund research to combat the virus.

It has also been linked with another rare condition called Guillain-Barre syndrome, per the Associated Press. Brazil and El Salvador have reported an alarming increase in the number of Guillain-Barre cases since the outbreak of the Zika virus in October 2015.

"Guillain-Barré syndrome is an autoimmune disorder in which the body usually is responding to another infection. It has an immune response that destroys the covering of nerves and interferes with the ability of nerves to function and survive," Dr. Bruce Hirsch of the North Shore University Hospital in New York told CBS News.

The U.S. has already reported several cases of the Zika virus with the Centers for Disease Control and Prevention issuing a travel warning in the 20 countries and territories mentioned above. They are encouraging pregnant women to cancel their planned trip to these areas and doctors to ask their pregnant patients about their travel history.