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Zika transmission through sweat, tears reported

Researchers from the University of Utah School of Medicine have reported a case in which it is likely that a patient contracted the Zika virus from the sweat or tears of another infected individual.

In correspondence published in the New England Journal of Medicine, the researchers describe two cases that they conclude indicate the spectrum of those at risk for Zika infection “may be broader than previously recognized.” They added that those who are not severely immunocompromised or chronically ill may also be at risk for a fatal infection.

“To date, 9 deaths from [Zika virus] infection that were unrelated to the Guillain–Barré syndrome have been confirmed in adults,” Sankar Swaminathan, MD, and colleagues wrote. “Here, 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 for [Zika virus] infection.”

According to the researchers, the first case involved a 73-year-old man who became the first person to die of Zika-related causes in the continental United States. He had been admitted to a hospital in Salt Lake City with hypotension and abdominal pain, 8 days after returning from a 3-week trip to the southwest coast of Mexico, an area with known Zika transmission. He reported being well during the trip, but said he had been bitten by mosquitos. After returning home, he began suffering from abdominal pain, pharyngitis and fever, followed by conjunctivitis, nonbloody diarrhea and myalgias, the researchers said. On the day of admission, he developed hypotension and dyspnea.

Tests for dengue virus, malaria and blood cultures were negative. Meanwhile, the patient’s health deteriorated, with progressive respiratory and renal failure, metabolic acidosis and hepatitis reported. He died on day 4 of hospitalization, not long after care was withdrawn. Later, serum testing for Zika virus on real-time polymerase chain reaction (PCR) assay was positive, with a threshold cycle of 17 and a very high viral load of approximately 2 x 10⁸ genome copies/mL, according to the researchers. RNA sequencing revealed a Zika strain 99.8% identical to one isolated from a mosquito in Chiapas, Mexico.

Five days after that death, patient 2, a previously healthy 38-year-old man who had visited the first patient in the hospital, began suffering from conjunctivitis, fevers, myalgia and facial maculopapular rash. After 7 days, urinalysis was positive for Zika virus, as was serum immunoglobulin M antibody. However, serum was negative on PCR assay.

Patient 2 reported wiping the first patient’s eyes during visitation, as well as assisting a nurse in repositioning patient 1 in bed without wearing gloves. No other exposure to bodily fluids, including blood and mucous membrane, were reported. No health care workers who had contact with patient 1 had developed symptoms. In addition, aedes species known to transmit Zika virus have not been found in the Salt Lake City area.

According to the researchers, it is likely that patient 2 acquired Zika virus infection from patient 1, because the former had not travelled to any Zika transmission area. They added that, given the high level of viremia in patient 1, infectious levels of the virus may have been present in sweat and tears, both of which patient 2 had contacted without gloves.

“The transmission of flaviviruses through intact skin or mucous membranes, although uncommon, has been shown in experimental animal models and in at least one human case,” Swaminathan and colleagues wrote. “Whether contact with highly infectious body fluids from patients with severe [Zika virus] infection poses an increased risk of transmission is an important question that requires further research.” – by Jason Laday

Disclosure: Swaminathan reports receiving grants from the NIH during the conduct of the study. Co-author Robert Schlaberg, MD, MPH, reports being the inventor of the Taxonomer, which was used in the analysis of this study, and is licensed to IDbyDNA Inc. by the University of Utah. The researchers report no additional financial disclosures.