The first case of nonsexual secondary Zika virus transmission has occurred in the United States, according to a research letter published by the New England Journal of Medicine.
“We report a rapidly progressive, fatal [Zika virus] infection acquired outside the United States and secondary local transmission in the absence of known risk factors,” wrote the authors of the report, led by Sankar Swaminathan, MD, of the University of Utah in Salt Lake City.
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The individual infected via secondary transmission, dubbed Patient Two in the report, is suspected to have contracted the disease from Patient One, a 73-year-old man who visited the southwestern coast of Mexico – a known hotbed of Zika virus – for a 3-week trip before returning to the United States. Eight days after returning, Patient One was admitted to a Salt Lake City hospital with symptoms consistent with a flavivirus infection and told doctors that he had been bitten by mosquitoes during his trip (N Engl J Med. 2016 Sep 28. doi: 10.1056/NEJMc1610613).
After undergoing tourniquet and laboratory testing, a diagnosis of dengue shock syndrome was made, but Patient One’s condition continued to deteriorate rapidly. Patient One died 4 days after initial hospitalization; real-time PCR assay confirmed Zika virus infection shortly thereafter.
Patient Two came into contact with Patient One during the latter’s hospitalization, reporting that he “assisted a nurse in repositioning Patient One in bed without using gloves,” according to the report. Patient Two began experiencing conjunctivitis, fever, myalgia, and a maculopapular rash on his face 5 days after Patient One died. The rash resolved itself after 7 days, and while PCR analysis of Patient Two’s serum was negative for Zika, his urinalysis was positive.
Because Patient Two had not traveled to a Zika-endemic area within 9 months of experiencing Zika-like symptoms and had not engaged in sexual intercourse with anyone who traveled to a Zika-endemic area, the authors conclude that he contracted the disease from contact with Patient One. The authors posit that, given the high levels of viremia in Patient One, the Zika virus could have been transmitted to Patient Two via sweat or tears, which Patient Two came into contact with while not wearing gloves. Local transmission via Aedis aegypti mosquito bite was highly unlikely to be the cause of transmission because of the lack of such mosquitoes in the Salt Lake City area.
“These two cases illustrate several important points,” the authors concluded. “The spectrum of those at risk for fulminant [Zika virus] infection may be broader than previously recognized, and those who are not severely immunocompromised or chronically ill may nevertheless be at risk for fatal infection.”