A 24-year-old housekeeper presented to hospital in Rio de Janeiro in June, 2014, with headache, fever, and a rash, 5 days after waking with a severe generalised headache, retro-orbital pain, weakness, and paraesthesia of the hands and feet. 2 days later she developed fever (axillary temperature 42 C), chills, and a pruritic rash on the face, abdomen, chest, and arms. By day 4, she was afebrile but had painful swelling of the hands (appendix) and feet, difficulty walking, and disseminated rash. She had had dengue 5 years previously, had not travelled recently, and did not recall any tick or mosquito bites. On examination, she was alert and fully oriented. Axillary temperature was 36· 7 C, pulse 90 beats per min, blood pressure 100/60 mm Hg, and respiratory rate 20 breaths per min. She had a diffuse erythematous macular rash, bilateral non-purulent conjunctival hyperaemia, enanthema of the palate, one enlarged painless cervical lymph node, and swelling of the hands and feet, but no signs of meningism. She had reduced strength in the legs, absent deep tendon reflexes at the knees and ankles, and both plantars were absent; sensation to light touch was reduced in the legs, but she had no urinary retention or ataxia. Examination, including neurological examination of the arms, was otherwise normal. Lumbar puncture (day 6), nerve conduction studies and an electromyogram (day 10), and a non-enhanced MRI (day 13) were normal. From day 10 the rash and swelling began to resolve with supportive treatment. By day 13 she was fully mobile and could be discharged. At follow-up on day 41, her only remaining symptom was persistent headache.

We investigated her serum and cerebrospinal fluid (CSF) for dengue, chikungunya, and Zika viruses. Realtime PCR for dengue and chikungunya was negative, but PCR was positive for Zika virus1 in serum (day 5), CSF (day 6), saliva (day 10), and urine (day 11). The CSF and acute and convalescent serum were negative for dengue and chikungunya by IgM-capture ELISA. Zika ELISA was not available. To identify the Zika virus genotype we sequenced 327 base pair amplicons encompassing the envelope protein, and identified the Asian lineage of Zika in the CSF (figure).