SARS-CoV-2 transmissible in tears of patients with moderate to severe COVID-19
COVID-19 may be transmitted through tears, as shown in some patients with laboratory-proven moderate to severe disease, according to a study. Conjunctival swab is a satisfactory method of collecting tears for assessing the presence of SARS-CoV-2 by reverse transcription polymerase chain reaction (RT-PCR).
“The respiratory tract is not the only transmission route, and considerable viral shedding occurs in the precorneal tear film in patients with moderate to severe COVID-19, thus implying that besides N95 respirators, use of goggles and face shields by healthcare workers should be mandatory when interacting with [these patients] to reduce the transmission of SARS-CoV-2,” the researchers said.
Seventy-eight patients with moderate to severe COVID-19 were enrolled in this cross-sectional study. Their tears were collected within 48 hours of laboratory confirmation using three methods: conjunctival swab plus Schirmer’s test strips (group 1), conjunctival swab (group 2), and Schirmer’s test strips (group 3). Samples from both eyes were transported in a single viral transport media for real-time RT-PCR.
The researchers also noted detailed demographic profiles, systemic symptoms, comorbidities, and ocular manifestations. They determined the viral load of a sample using cycle threshold (Ct) value of E gene. A specimen was deemed positive if the amplification curve for the E gene crossed the threshold line within 35 cycles and if it showed positive results on an RNA-dependent RNA polymerase or open reading frame 1b gene assay.
Samples from three patients were found to be inadequate for analysis. Of the remaining patients, 36 (48 percent) had moderate disease and 39 (52 percent) had severe disease, with no ocular involvement in any patient. [Ophthalmology 2021;128:494-503]
In RT-PCR analysis of tears, positive results were found in 18 patients (24 percent) and in 29 of 225 samples (12.5 percent). Positive results were detected in 11 patients (14.7 percent) in group 1, 11 (14.7 percent) in group 2, and seven (9.3 percent) in group 3 (p=0.3105).
Mean Ct values in the respective groups were 28.36±6.15, 29.00±5.58, and 27.86±6.46 (p=0.92). Five patients showed positive RT-PCR results by all three methods (mean Ct value, 25.24±6.33), while 12 did by any of these methods (mean Ct value, 32.16±1.94), with the difference in Ct values being statistically significant (p=0.029). Additionally, the median value of symptomatology in patients who tested positive in RT-PCR analysis of tears was 5 days (range, 4–9 days).
“The role of the ocular surface as a possible portal of entry, reservoir for replication, and transmission of SARS-CoV-2 RNA has been explored extensively,” the researchers said. “Differences in detection of viral RNA in tears have ranged from 0–7 percent, with some researchers claiming minimal viral shedding in ocular secretions.” [Ocul Immunol Inflamm 2020;28:714-720; J Med Virol 2020;92:589-594; Ophthalmology 2020;127:982-983; JAMA Ophthalmol 2020;138:575-578; J Clin Med 2020;9:1269]
Earlier studies have found ocular manifestations of COVID-19 along with other clinical features, such as conjunctivitis and keratoconjunctivitis. Patients also showed ocular symptoms, including itching, redness, tearing, discharge, and foreign body sensation. [Ophthalmology 2020;127:982-983; Can J Ophthalmol 2020;55:e125-e129; J Fr Ophthalmol 2020;43:389-391]
The current study was limited by its small sample size, the noninclusion of patients with mild and asymptomatic COVID-19, and the one-time sampling.