WASHINGTON — President Barack Obama is asking Congress for more than $1.8 billion in emergency funding to fight the Zika virus and the mosquitoes that spread it here and abroad, but says “there shouldn’t be a panic on this.”

The virus is spreading rapidly through Latin America. While most people experience either mild or no symptoms, Zika is suspected of causing a birth defect — babies born with abnormally small heads — and pregnant Americans are urged to avoid travel to affected areas.

U.S. health officials say the money is critical for research into the birth defect known as microcephaly. They also want to speed development of a vaccine and better diagnostic tests, and expand mosquito control programs.

“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.