WASHINGTON (AP) — President Barack Obama is asking Congress for more than $1.8 billion in emergency funding to help fight the Zika virus. In an announcement Monday, the White House said the money would be used to expand mosquito control programs, speed development of a vaccine, develop diagnostic tests and improve support for low-income pregnant women.

Zika virus disease is mainly spread by mosquitoes. Most people who catch it experience mild or no symptoms. But there are suspicions that the fetus of infected pregnant women may be at risk for a rare birth defect that causes brain damage and an abnormally small head.

"What we now know is that there appears to be some significant risk for pregnant women and women who are thinking about having a baby," Obama said in an interview aired Monday on "CBS This Morning."

He added, however, that "there shouldn't be a panic on this."

The Pan American Health Organization reports 26 countries and territories in the Americas with local Zika transmission, the White House noted. To date, there has not been transmission of the Zika virus by mosquitoes within the U.S., but some Americans have returned to the U.S. with Zika infections from affected countries in South America, Central America, the Caribbean and the Pacific Islands.

The Centers for Disease Control and Prevention reports 50 laboratory-confirmed cases among U.S. travelers from December 2015- February 5, 2016, the White House said.