The deadly Zika virus can cause birth deformities and small heads in babies born to infected mothers. There is currently nor cure or antidote.
Earlier this week, cases were reported in Texas. Now, the first two cases have been reported in Pennsylvania. Both people had travelled to countries which are infected. And on Tuesday, a case was reported in Delaware.
Zika can be only mildly harmful for many people, but for pregnant women it can be deadly for their babies. There is particular concern this year since the disease is centered in Brazil and Brazil is scheduled to host the 2016 Olympics with potentially millions of visitors.