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9 of the worst viruses on Earth

By: Mary Jo DiLonardo on Dec. 9, 2019, 8:36 a.m.
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This once-obscure virus has been wreaking havoc recently, especially in the Americas. The WHO declared Zika a global public health emergency, especially because of newfound links with birth defects and other potentially severe health problems.

Zika is transmitted by infected Aedes mosquitoes like Aedes aegypti and Aedes albopictus, also known as the Asian tiger mosquito. Although only about one in five people infected with Zika virus will get sick, according to the CDC, the virus is linked to microcephaly, a birth defect characterized by an undersized head and incomplete brain development.