Zika outbreak prompts travel warning in Miami

Global outbreak has led to more than 1,800 serious birth defects

In a highly unusual travel warning, health officials advised pregnant women to avoid a part of Miami where mosquitoes are apparently transmitting Zika directly to humans.

Health officials on Friday announced that mosquitoes have apparently started spreading Zika on the US mainland, citing four cases they strongly believe were caused by bites. Ten more cases were announced on Monday, even though Florida authorities have yet to find any mosquitoes actually carrying the virus.