Presence of SARS-CoV-2 on the conjunctival mucosa in patients hospitalized due to COVID-19: Pathophysiological considerations and therapeutic implications

Physiol Int. 2022 Nov 21;109(4):475-485. doi: 10.1556/2060.2022.00113. Print 2022 Dec 14.


Introduction: Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resulted in a worldwide pandemic, due to its great capacity to invade the human body. Previous studies have shown that the primary route of invasion of this virus is the human respiratory tract via the co-expression of ACE2 receptor and TMPRSS2, a serine protease on the cellular surface. Interestingly, this condition is present not only on the respiratory epithelium but on the conjunctival mucosa, as well. Thus, we hypothesized that SARS-CoV-2 is present on the conjunctival mucosa.

Aim: To prove that SARS-CoV-2 can be detected in the conjunctiva.

Methods: Previously nasopharyngeal swab-sample based real-time polymerase chain reaction (PCR) positive COVID-19 infected patients were selected at the COVID Care Centers of Semmelweis University, Budapest, Hungary. The study was approved by the ethical committee of Semmelweis University. During their recovery, both nasopharyngeal and conjunctival swab-samples were taken and PCR method was used to detect the presence of SARS-CoV-2 RNA. Appropriate statistical analysis was performed.

Results: The study population consisted of 97 patients, 49 females (50.5%) and 48 males (49.5%), with a mean age of 67.2 ± 11.9 years. During recovery, with nasopharyngeal swabs, the PCR test was positive in 55 cases (56.70%), whereas with conjunctival swabs it was positive in 8 cases (8.25%). Both tests were positive in 5 cases (5.15%). In some patients, ocular symptoms were observed as well. The rest of the patients (29 cases) had negative nasopharyngeal PCR tests during recovery.

Conclusions: Although only in few cases, the data of the present study provides a proof of concept that SARS-CoV-2 can be present on the conjunctival mucosa even in nasopharyngeal negative patients, a finding, which can have clinical importance. Also, on the basis of these findings one can hypothesize that - in addition to the respiratory tract - the conjunctiva can be an entrance route for SARS-CoV-2 to the human body. Thus, in high-risk conditions, in addition to covering the mouth and nose with mask, the protection of the eyes is also strongly recommended.

Keywords: COVID-19; PCR; SARS-CoV-2; conjunctiva; ocular symptoms; polymerase chain reaction.

MeSH terms

  • Aged
  • COVID-19* / diagnosis
  • Conjunctiva / chemistry
  • Female
  • Humans
  • Male
  • Middle Aged
  • Mucous Membrane / chemistry
  • RNA, Viral / analysis
  • SARS-CoV-2*


  • RNA, Viral