Zika linked to neurological defects

The Zika virus, which is linked to microcephaly – small brains in newborn children – may also cause a swelling of the brain that attacks the central nervous system in a similar way to multiple sclerosis

Zika virus: Infects blood system. Common symptoms include fever, joint pain, conjunctivitis, muscle pain, rash and
headache.

Zika virus

Symptoms are usually mild, and last several days to a week

Immune system: Body’s defence against foreign invaders. Killer T-cells – type of white blood cell – find and destroy infected cells, and virus

Zika virus and pregnancy: Zika has been found in amniotic fluid of women during pregnancy, suggesting virus can cross placental barrier and potentially infect foetus

Brain: New study discovers that Zika infects cells in cortex – brain’s outer layer. How virus crosses protective blood-brain barrier remains unclear

Spinal cord

Nerve

Myelin sheath

Axon

Exposed nerve fibre

Damaged myelin

Healthy neuron (representative diagram)

Dendrites: Receive signals from other neurons

Cell body: Control centre and site of information processing Impulses to and from brain

Axon: Long nerve fibre carries information as electrical impulses

Myelin sheath: Insulates axon

Central nervous system (CNS): Virus is associated with disorders that attack CNS – brain, spinal cord and optic nerves

ADEM: Two Zika victims have also developed acute disseminated
encephalomyelitis – inflammation of CNS in which myelin and axon is damaged. Neuron is unable to conduct signals

Sources: CDC, Science, Lancet, American Academy of Neurology, Johns Hopkins University 

Picture: Purdue University, courtesy of Kuhn and Rossmann research groups