In a study published online by JAMA Ophthalmology, Changwen Ke, Ph.D., of the Guangdong Provincial Center for Disease Control and Prevention, Guangzhou, China and colleagues examined whether Zika virus (ZIKV) could be detected from conjunctival swab samples of laboratory-confirmed ZIKV cases.

The clinical symptoms of ZIKV infection are mostly a mild and self-limited rash, joint pain, and conjunctivitis (also known as pink eye). More than 80 percent of ZIKV infections are asymptomatic. Severe eye damage in infants with microcephaly was associated with ZIKV infection. However, it has not been clear whether the eye lesions are the result of microcephaly or directly ZIKV infection.

Since February 12, 2016, 11 ZIKV infection cases (Chinese travelers) were imported from Venezuela in Guangdong, China. All the cases were confirmed to be ZIKV infection by real-time reverse-transcription polymerase chain reaction. Serum and conjunctival swab samples were taken from 6 of 11 cases. The ZIKV RNA was detectable in serum no more than 5 days after symptom onset, but it was detected in conjunctival swab samples until day 7 in case 5.

"Detection of ZIKV RNA is a gold standard of confirmation of ZIKV infection. In this study, we described the direct detection and isolation of ZIKV from conjunctival swab samples. Although isolation of ZIKV in cell culture from urine, semen, saliva, and breast milk has been described, to our knowledge, detection and isolation of ZIKV from conjunctiva has not been reported so far. These results, though, are not sufficient to recommend the use of conjunctival swabs as alternative samples for ZIKV diagnosis because of shorter persisting and shedding time of ZIKV in conjunctiva fluid (<7 days) compared with urine and saliva samples (<20 days)," the authors write.

"It may have implications for transmission of ZIKV, e.g., through corneal graft donors, although this report does not provide direct evidence to support that indication. Nevertheless, epidemiological data and experimental studies are needed to assess the further significance of this finding because of increasing complications caused by ZIKV infection in neonates."