A tropical infection new to the Western Hemisphere. The Zika virus is a mosquito-transmitted infection related to dengue, yellow fever and West Nile virus. Although it was discovered in the Zika forest in Uganda in 1947 and is common in Africa and Asia, it did not begin spreading widely in the Western Hemisphere until last May, when an outbreak occurred in Brazil.

Until now, almost no one on this side of the world had been infected. Few people here have immune defenses against the virus, so it is spreading rapidly. Millions of people in tropical regions of the Americas may now have been infected.

Yet for most, the infection causes no symptoms and leads to no lasting harm. Scientific concern is focused on women who become infected while pregnant and those who develop a temporary form of paralysis after exposure to the Zika virus. via nytimes.com

ATTENTION Zika Virus NEWS February 11 2016 Two U.S. women who contracted the Zika virus while traveling out of the country miscarried after returning home, and the virus was found in their placentas, a spokesman for the Centers for Disease Control and Prevention said Thursday.

Federal health officials have not previously reported miscarriages in American travelers infected with the mosquito-borne virus while abroad. But there have been miscarriages reported in Brazil, the epicenter of a Zika epidemic that now spans nearly three dozen countries. Researchers in Salvador, Brazil's third largest city, are investigating some miscarriages and still births at three maternity hospitals for possible links to Zika.

As many as 1.5 million Brazilians may have been infected with the mosquito-borne Zika virus and now the U.S. and other countries are also reporting news cases. But what is the Zika virus? And why does it pose a threat to pregnant women? Dipti Kapadia explains