Still many questions about Zika's threat to pregnant women

WASHINGTON (AP) — Zika may stand convicted of causing devastating birth defects but there still are lots of questions about how much of a threat the virus poses to pregnant women, and what to do about it.

[...] mosquitoes aren't spreading Zika in the mainland U.S. That means for now, the main advice for pregnant women here is to avoid travel to Zika-affected parts of Latin America or the Caribbean.

Here are some questions and answers about what experts know, and need to learn, as the first mosquito-borne virus known to cause birth defects inches closer to the U.S.

Zika had been considered a nuisance virus until a massive outbreak began last year in Brazil and doctors there reported babies being born with unusually small heads, called microcephaly.

Last week, the U.S. Centers for Disease Control and Prevention said Zika was indeed the culprit — and that it caused a particularly severe form of microcephaly, with serious underlying brain damage, as well as other brain-related abnormalities.

Studies increasingly show Zika gets into a fetus' developing brain and kills cells, or stops them from growing further, and even can kill the fetus.

In another study, ultrasound exams spotted some sort of abnormality, not just microcephaly, in nearly 30 percent of women who had Zika during pregnancy.

The CDC says women who traveled to a Zika-affected area or who became infected should wait eight weeks before attempting conception.

No, but they do expect local clusters of cases — just like has happened in previous years with a Zika relative named dengue fever that's spread by the same mosquito, a species named Aedes aegypti.

NIH's Fauci hopes to begin small safety steps of a candidate by September but that wouldn't make any dent in the Latin American outbreak.

Zika also has been linked to a nerve disorder called Guillain-Barre syndrome that can be triggered by various infections, and there have been occasional reports