The presence of Zika virus RNA in human tears 30 days post-illness was shown in patients with polymerase chain reaction (PCR)-confirmed Zika virus infection, according to results published in Nature Scientific Reports.
The outbreak of Zika virus throughout the Pacific islands, southeast Asia, and the Americas has been associated with severe neurologic complications such as microcephaly in infants. Ocular developmental anomalies in some infants with microcephaly and 2 cases of Zika virus-associated uveitis in adults have also been reported. Presence of Zika virus RNA in tears was previously shown, but how long the virus remains localized has been unclear; therefore, conjunctival swabs taken at day 30 days post-illness from 29 patients admitted to the Communicable Disease Centre at Tan Tock Seng Hospital, Singapore, from August 29, 2016, to November 15, 2016, were tested for Zika virus RNA.
The lowest limit of detection for Zika virus RNA in spiked swabs with different concentrations of Zika virus (plaque-forming unit [PFU]/μL) using real time reverse-transcription PCR was determined to be 0.1 PFU/μL, equivalent to copy number of 4.9. Swabs from 3 patients were positive for Zika virus, and the estimated viral loads ranged from 5.2 to 9.3 copies. Two of these patients experienced conjunctivitis and one had retro-ocular pain.
This is the first report of Zika virus RNA in conjunctiva during the late convalescent stage of disease. The detection limits using this protocol and its noninvasive nature mean conjunctival swabs could be a useful diagnostic tool. Further, the results are of clinical significance, demonstrating ocular transmission of Zika virus may be possible even at the late convalescent stage of infection.
Tan JJL, Balne PK, Leo Y-S, Tong L, Ng LFP, Agrawal R. Persistence of Zika virus in conjunctival fluid of convalescence patients. Sci Rep. 2017;7:11194.