Could the SARS-CoV-2 Infection be Acquired via the Eye?

Abstract

The COVID-19 outbreak was first identified in the Hubei province of Wuhan, China, in December 2019. It is caused by SARS-CoV-2. The proposed transmission of SARS-CoV-2 is respiratory droplets < 5 μm in diameter or by indirect or direct human-to-human contact. SARS-CoV-2 may also be transmitted through the eyes. The receptor for SARS-CoV-2 is angiotensin-converting enzyme 2 (ACE-2). SARS-CoV-2 replicates at the binding site on the surface of target cells, such as ocular tissues, leading to the cleavage of the ACE-2 receptor, activation of the spike protein, and inflammation in the form of ocular manifestations such as conjunctivitis, anterior uveitis, retinitis, and optic neuritis. SARS-CoV-2 can cause eye manifestation. ACE-2 is expressed by conjunctival epithelial cells, and the presence of ACE-2 is significantly elevated in conjunctival cells for patients with conjunctivitis, conjunctival nevi, conjunctival papilloma, conjunctival cysts, and conjunctival polyps’ epithelial cells compared to control subjects. It has been reported that ocular surface cells were potential infection sites of SARS-CoV-2. The proteases of ocular surface cells facilitate the binding of SARS-CoV-2 on the viral spike protein to the ACE-2 receptor in the conjunctiva, limbus, and cornea. SARS-CoV-2 might exist in tears since there was an expression of ACE-2 on the transmembrane serine protease 2 (TMPRSS2). Another study found that SARS-CoV-2 was present on conjunctiva swabs from two out of 11 (18.2%) patients tested for SARS-CoV-2 via nasopharyngeal swabs. A common symptom was conjunctivitis, and SARS-CoV-2 could be transmitted by aerosol contact with the conjunctiva. However, the risk of SARS-CoV-2 transmission through tears was low. In a study of 17 patients, none of the 32 patient tear samples was positive for SARS-CoV-2. The replication of SARS-CoV-2 was much more efficient than that of SARS-CoV in human conjunctiva and the upper respiratory airways. Thus, eyes could be a potential route of SARS-CoV-2 transmission. All of the above information demonstrates that SARS-CoV-2 might be acquired through the eyes, wearing a face shield could benefit, especially during aerosol-generating procedures.

Keywords