NEW YORK (AP) -- The University of Pittsburgh says one of its researchers became infected with the Zika virus in a lab accident.

The scientist accidentally stuck herself with a needle last month during a Zika experiment. She developed Zika symptoms last week and lab tests confirmed the infection.

Pitt officials on Thursday said the researcher has recovered and returned to work.

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The virus is spread mainly through the bite of a tropical mosquito. It causes only a mild and brief illness, at worst, in most people. But it can cause fetal deaths and severe birth defects in the children of women infected during pregnancy.

Nearly 700 infections have been reported in the 50 states. All were people who had traveled abroad, or who had sex with someone who did.