– Microcephaly is a fairly uncommon condition in most parts of the world, but currently it is a big concern in parts of South America, where Zika is spreading quickly. According to the Mayo Clinic, microcephaly is “a rare neurological condition in which an infant’s head is significantly smaller than the heads of other children of the same age and sex. Sometimes detected at birth, microcephaly usually is the result of the brain developing abnormally in the womb or not growing as it should after birth.” This disease can be caused by a number of factors, including genetic factors as well as environmental factors, such as Zika.