Zika Virus Outbreak Prompts CDC to Activate Highest Emergency Ops Level

This is only the fourth time that the highest level has been activated.

The Level 1 activation is "reflecting the agency’s assessment of the need for an accelerated preparedness to bring together experts to focus intently and work efficiently in anticipation of local Zika virus transmission by mosquitoes," the agency said in a statement.

Common symptoms of the Zika virus include fever, rash, joint pain and conjunctivitis, according to the CDC. Approximately one in five people infected with the virus show symptoms. The virus has also been associated with a rise of microcephaly birth defect cases in Brazil. The birth defect is characterized by a malformed or smaller head and brain and can result in serious developmental delays.

Guillain-Barre syndrome is an immunological reaction that can occur after viral or bacterial infections.