The Eye: a Possible COVID-19 Reservoir
Covid-19 has been known to manifest in other regions apart from the respiratory tract, including the gastrointestinal tract and ocular tissues, as already reported in the previous article.
Human-to-human transmission occurs mainly through respiratory droplets; however Covid-19 has been detected in several body fluids, including ocular secretions.
An observational study conducted by Lazzaro Spallanzani National Institute for Infectious Diseases Hospital demonstrated the early detection of infectious SARS-CoV-2 in ocular fluids from a patient with the first confirmed case of Covid-19 in Italy. The Spallanzani Institute in Rome was the first research centre in Europe to isolate the genomic sequence of SARS-CoV-2. A 65-year-old woman, travelled from Wuhan, China, to Italy on the 23rd January 2020 and was admitted to Spallanzani Hospital on the 29th January 2020, 1 day after symptom onset.
At admission to the high isolation unit at the Hospital, she presented with a non-productive cough, sore throat, rhinitis, and bilateral conjunctivitis. Fever (38°C), nausea, and vomiting began at day 4. Infection with SARS-CoV-2 was confirmed by performing real-time reverse transcription polymerase chain reaction (RT-PCR) assay on sputum samples.
On day 3 after hospital admission, owing to the persistence of conjunctivitis, an ocular swab was collected, and viral RNA was detected. Subsequent ocular samples collected, at almost daily frequency, remained positive up to day 21, with declining virus concentration. Conjunctivitis greatly improved at day 15 and appeared resolved on day 20. Five days after it became undetectable, SARS-CoV-2 RNA was detected again in the ocular swab sample collected at day 27, being present in ocular swabs days after it was undetectable in nasal swabs.
For this reason, it was hypothesised that there remained sustained replication in conjunctival tissue, evidenced by the presence of viral genomes detected in ocular swabs, signifying infectious virus. This RNA-positive inoculated sample confirmed viral replication.
These findings highlight the importance of infection control measures (i.e. frequent hand washing and avoid touching of the eyes, nose and mouth); the importance of the use of personal protective equipment (PPE) for ophthalmologists, during clinical examination; and also the use of appropriate eye products, e.g. single-dose eye drops, because ocular mucosa may not only be a site of virus entry but also a source of contagion.
F. Colavita, D. Lapa et al; SARS-CoV-2 Isolation From Ocular Secretions of a Patient With COVID-19 in Italy With Prolonged Viral RNA Detection; Annals of Internal Medicine, 17 April 2020 doi.org/10.7326/M20-1176
Images by National Institute of Allergy and Infectious Diseases (NIAID) (CC-BY-2.0)