Assessing Viral Shedding and Infectivity of Tears in Coronavirus Disease 2019 (COVID-19) Patients
Ivan Yu Jun Seah, Danielle E. Anderson, Adrian Eng Zheng Kang, Linfa Wang, Pooja Rao, Barnaby Edward Young, David Chien Lye, Rupesh Agrawal. Ophthalmology. March 24, 2020. Published:March 24, 2020 DOI:https://doi.org/10.1016/j.ophtha.2020.03.026
With the emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), new questions regarding the safety of patients and healthcare providers have emerged. While the virus is known to be transmitted via droplets, it is unclear if alternative transmission modes exist. Whether viral transmission may occur through infected ocular fluid or tissue is controversial. It has been hypothesized that the nasolacrimal system could act as a conduit for virus to travel from the upper respiratory tract to the eye.
In this study, the authors attempted to determine whether tears might represent a possible source of transmission by assessing for the presence of SARS-CoV-2 with viral isolation and quantitative reverse-transcription polymerase chain reaction (RT-PCR). In a prospective study in Singapore, seventeen patients with COVID-19 diagnosed by RT-PCR from nasopharyngeal swabs were studied.
Tears were sampled using a Schirmer test at varying time points between days 3 and 20 after initial development of symptoms. Samples were used to inoculate Vero-E6 cells. After 4 days of incubation, cells were evaluated for viral presence by RNA extracted and quantitative RT-PCR. Fourteen patients showed upper respiratory tract symptoms at presentation and 1 patient developed conjunctival injection and chemosis. A total of 64 samples were obtained over the study period. All tear samples showed negative results on viral isolation and RT-PCR.
In summary, no evidence of SARS-CoV-2 could be found in tear samples of infected individuals, even when nasopharyngeal swabs continued to show positive results. Viral transmission through tears regardless of the phase of infection is likely low.