The current outbreak of the Zika virus across large swaths of South America presents a public health threat of "alarming proportions" and could affect as many as 4 million people, the World Health Organization (WHO) warned on Jan. 28.

Margaret Chan, the U.N. health agency's director general, reiterated the disease has become associated with neurological complications, as thousands of women infected with the virus have given birth to severely or mortally disabled infants. The WHO will now convene an International Health Regulations Emergency Committee meeting on Feb. 1, according to a statement.

WHO 'Scaling Up Surveillance Systems'

The agency was "supporting the scaling up and strengthening of surveillance systems in countries that have reported cases of Zika and of microcephaly and other neurological conditions that may be associated with the virus," it noted in the statement.

The Geneva-based organization also promised that it would heighten surveillance in affected countries and "convene experts to address critical gaps in scientific knowledge about the virus and its potential effects on fetuses, children and adults."

Zika 'Spreading Explosively,' WHO Warns

Chan, meanwhile, warned on Jan. 28 that the Zika virus is "spreading explosively" in the Americas, Voice of America reported.

"As of today, cases have been reported in 23 countries and territories in the [Americas] region," Chan said.

"The level of alarm is extremely high. Arrival of the virus has been associated with a steep increase in the birth of babies with abnormally small heads."

Virus Originated in Africa, Spread to Brazil in 2015

The Zika virus, a mosquito-transmitted infection, was discovered in the Zika forest in Uganda in 1947 and is common in Africa and Asia, The New York Times reported. After an outbreak in Brazil last May, it began spreading widely in the Western Hemisphere.

The U.S. Centers of Disease Control and Prevention (CDC) now recommend that pregnant women avoid travel to almost 30 destinations, including Bolivia, Brazil, Cape Verde, Colombia, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Haiti, Honduras, Mexico, Panama, Paraguay, Suriname and Venezuela; a number of Caribbean islands; as well as Puerto Rico and the U.S. Virgin Islands.