Zika Virus Infection Without Known Risk Factors

New information about the epidemiology and complications of Zika virus (ZV) infection is accruing rapidly. We now know that this infection can be transmitted by certain Aedes mosquitos as well as bidirectionally through sexual contact (both from male to female and female to male), even when the transmitting partner is asymptomatic.

Now, researchers report acquisition in Utah in July 2016 of ZV by Patient A, whose only risk factor was close contact with an elderly index patient (a family member) who had returned from a Zika-endemic area. Patient A had not traveled to an endemic area, did not have sexual intercourse with someone who had traveled, and did not receive blood transfusion, organ transplantation, or mosquito bites. Patient A hugged, kissed, and helped care for the index patient and held him while others disposed of the index patient's stool. The index patient developed septic shock and died in the hospital on June 25, 2016. A blood specimen taken from the index patient two days before death had a viremia level 100,000 times the average for patients with ZV infection.

Patient A developed fever, rash, and conjunctivitis six days after the index patient's death. On day 7 of Patient A's illness, his urine was positive for ZV by real-time reverse transcription-polymerase chain reaction, and four days later, after resolution of the illness, his serum was positive for immunoglobulin M and plaque neutralizing antibodies to ZV. All of 19 other family contacts of the index patient were negative for ZV symptoms and infection. Testing of neighbors and healthcare workers involved in the index patient's care has identified no ZV infection but is ongoing. No Aedes mosquitos were detected in the area.