Government fumigators prepare to spray homes for mosquitoes in Havana, Cuba, Feb. 22, 2016.
Government fumigators prepare to spray homes for mosquitoes in Havana, Cuba, Feb. 22, 2016.

WASHINGTON - Some 500 million people in the Americas and the Caribbean are at risk of getting the Zika virus. So far, 37 countries and territories are reporting transmission of the virus. Peru is the latest country to report transmission. The virus is also in Saint-Barthélemy, a French territory in the Caribbean. The virus itself is largely inconsequential, but doctors and medical scientists involved in public health say getting across the message that a mild disease could be devastating to unborn babies is challenging.

Zika causes microcephaly, a birth defect where the head and brain are abnormally small, but as of yet, researchers don't know what percentage of pregnant women who get the virus end up delivering babies with microcephaly. One study shows a one percent risk. Another small study puts the risk at 29 percent.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said no one knows the true risk. A much larger study is now being conducted but until the results are in, the best answer is, "We don't know," Fauci said.

So far, most cases of microcephaly have been reported in Brazil, but cases have also been reported in Colombia, Panama, Martinique and the United States. The Zika virus is also associated with a form of paralysis called Guillian-Barre syndrome. Seven countries have reported cases of Guillian-Barre which can be fatal.

The only protection against this mosquito-bourne virus is not to get bitten or not to get pregnant, as women in some countries have been advised. The problem is the Aedes aegypti mosquito that carries the Zika virus is hard to contain. It prefers human blood to that of animals, and it likes to live indoors. It's also a day-time biter. In many parts of the Americas, birth control is not readily available, another complicating factor. The only answer lies in the development of a vaccine. One will be tested on humans by September, but it could still be at least three years before it becomes available.

Meantime, helping children born with microcephaly is expensive. Some may need lifelong care.

"What we see now is the tip of the iceberg," said Dr. Sylvain Aldighieri, the Zika Incident Manager for the Pan American Health Organization. Aldighieri added that these children, even those without microcephaly but whose mothers had Zika while pregnant, will have to be followed for a period of two to four years in order to understand the extent of the damage.

Microcephaly can cause blindness, physical deformities beyond small heads, and can affect the intellect. 

Aldighieri and Fauci spoke at a press conference at the Pan American Health Organization's headquarters in Washington, D.C.

The U.S. Congress has not yet approved $1.9 billion in emergency funding that President Obama requested in February. Fauci said the funding "is absolutely essential." He said he had to move money from programs on malaria, influenza and tuberculosis to provide funds for Zika research.

Without the additional funds, "We cannot do the job that needs to be done." he said.

Fauci expects the virus to be transmitted in the U.S., but he also said Zika is likely to be contained such as similar viruses like dengue and chikungunya have been contained in the past.