In most cases, illness from Zika virus infection is mild. Many people don’t have any symptoms, and when they do, they generally have fever, rash, joint pain, or red, watery eyes (conjunctivitis).
For pregnant women and newborns, it’s a different matter. Scientists have now concluded that Zika virus infection can cause a birth defect called microcephaly, an abnormally small brain and skull. Zika has also been linked to other problems in newborns, such as eye defects, hearing loss, and impaired growth. So while Zika illness is usually pretty mild in most adults, it’s deeply concerning for pregnant women and their babies. Researchers are still investigating Zika infections during pregnancy. For example, we don’t know why some infected pregnant women have babies that are healthy and others have babies with birth defects. And we don’t know when during the pregnancy the infection might cause harm to the fetus.
A small proportion of Zika infections have been linked to Guillan-Barré Syndrome (GBS), which causes muscle weakness and sometimes paralysis. CDC is still investigating this, but it appears likely that Zika triggers GBS.