Can the new coronavirus be transmitted through the eye conjunctiva? On March 14, local time, bioRxiv, a bioscience preprint platform, published a new study on the spread of new coronavirus disease (COVID-19) through the eye conjunctiva “Rhesus macaques can effective bely infected with S 1 ARS-CoV-2 via ocular conjunctival route.”
For the first time, the Qinchuan team of the Institute of Medical Experimental Animals of the Chinese Academy of Medical Sciences has found experimental evidence that the new coronavirus can be transmitted through conjunctiva, that is, rhesus monkeys can effectively infect the new coronavirus through the conjunctiva pathway, which provides important theoretical support for virus prevention, especially the protection of medical personnel.
Based on clinical symptoms, viral load testing, and serological examination, the authors found that rhesus monkeys can infect the new coronavirus through conjunctiva pathway, and that the virus can be transferred from the conjunctiva to the respiratory tract and other tissues one day after infection.
The study’s team from the Institute of Medical Experimental Animals of the Chinese Academy of Medical Sciences and Beijing Anzhen Hospital, affiliated with Capital Medical University, were published by Qin Chuan, director of the Institute of Medical Experimental Animals of the Chinese Academy of Medical Sciences and an expert on special allowances from the State Council. As a specialist in comparative medicine and pathology, Qin Chuan was responsible for participating in the “Establishment of THE SARS Infection Animal Model” in 2003, and also led the team in animal model experiments on various infectious diseases.
The outbreak of COVID-19 is highly contagious and it is now widely believed that the new coronavirus is transmitted mainly through human-to-human respiratory droplets or direct close contact, almost as many other potential routes of transmission are yet to be further studied.
In previous clinical cases, patients with SARS (Severe Acute Respiratory Syndrome) and COVID-19 had detected viral RNA in tear and conjunctiva secretion samples.
Earlier, Wang Guangfa, a member of the National Health and Health Commission’s expert group and director of the Department of Respiratory and Critical Medicine at Peking University’s First Hospital, went to work in Wuhan and was diagnosed with the new coronavirus infection, but also speculated that his route of infection may have been the virus first into the eye conjunctiva and then to the whole body.
But at the same time, Wuhan University People’s Hospital Chen Changzheng team and other research groups have also said that the new coronavirus can be detected in the conjunctiva sacs of patients with new coronary pneumonia, but clinical analysis data do not support the transmission of the new coronavirus through the conjunctiva route.
In the latest study, the researchers vaccinated three rhesus monkeys aged 3 to 5 with a certain dose of infection (TCID50) of the new coronavirus, randomly selected two of them for an eye conjunctiva and one through trachea injection. In order to compare the distribution and pathogenesis of the host infected with the new coronavirus by different means. The researchers inoculated the rhesus monkeys in a single way to ensure their exact route of infection.
The researchers observed the clinical signs of rhesus monkeys on a daily basis and found no significant clinical changes in the weight or temperature of rhesus monkeys infected by the virus in both ways. The team collected regular specimens, including nasal swabs and throat swabs, 0, 1, 3, 5 and 7 days after vaccination.
In addition, the team collected conjunctiva swabs and swabs from rhesus monkeys to explore potential routes for the release of new coronaviruses in the host body.
Notably, on the first day after vaccination, researchers were able to detect viral load in the conjunctiva swabs of rhesus monkeys infected by the eye conjunctiva, but then could no longer detect the virus in the conjunctiva. This means that the new coronavirus may be transferred from the conjunctiva to the respiratory tract and other tissues, the team said.
One to seven days after vaccination, the nasal swabs and throat swabs of the three rhesus monkeys were able to continuously detect viral loads.
In addition, 14 days and 21 days after the conjunctiva inoculation of the new coronavirus, specific IgG antibodies against the new coronavirus can still be detected in the two rhesus monkeys, indicating that they are indeed infected with the new coronavirus.
For swabs, although no viral load has been detected in rhesus monkeys with conjunctiva inoculationviruses, they can be continuously detected in rhesus monkey samples that are inoculated by injection through the trachea.
Seven days after the virus was inoculated, the researchers euthanized the rhesus monkey swashes in the trachea and one of the conjunctiva monkeys and performed an autopsy.
For conjunctiva-inoculated rhesus monkeys, the viral load is mainly distributed in: nasal tear duct system and intra-eye, including the tear glands, optic nerve and conjunctiva nasal cavity; The groin and rectum (lymph nodes), stomach, duodenum, intestinal and intestinal.
Three rhesus monkeys who were vaccinated with the virus 0, 1, 3, 5 and 7 days after the inoculation of the eye conjunctiva, nose, throat and swab specimens of the virus load, C-1 and C-2 represent edges the virus, IT-1 is the rhesus monkey inthes of the trachea pathway inoculated
In contrast, the distribution of the virus in rhesus monkeys, which are inoculated through the trachea, varies. Virus replication mainly occurs in the lungs, and the nasal interstitas, trachea, jawly nodes, tonsils, lung lymph nodes and part of the digestive tract (including the blind intestine, colon, duodenum and empty intestine) are also relatively high in viral load.
Notably, researchers have detected viruses in different parts of the river monkey’s digestive tract, suggesting that the digestive system may be susceptible to new coronavirus infections.
Compared with rhesus monkeys who were inoculated by the intra-trachea, the viral load and distribution in the conjunctiva-infected rheumatosis monkeys were relatively high, but relatively light and local in the lungs. However, both pathways can cause gastrointestinal infections.
These experimental results show that conjunctiva is the gateway to the spread of new coronaviruses. The researchers were able to detect viral loads in the tissues associated with several nasal tear systems, especially in the conjunctiva, tear glands, nasal cavity and throat, which act as a “bridge” between the movement of the virus between the eyes and respiratory tissues.
It is worth noting that the tear duct sits as a catheter for collecting and transporting tears from the surface of the eye to the nasal passages below the nose, and also facilitates the diversion of the virus from the eye tissue to the respiratory tissue.
In fact, previous reports have shown that while conjunctiva, sorceic or cornea absorbs fluids containing the virus, most liquids, including tears and secretions, are discharged into the nasopharynx cavity or swallowed. The epithelial of the tear ingress may also help to absorb the tear.
The results are also highly consistent with the anatomical characteristics of viruses entering the host through conjunctiva pathways. Researchers say the current approach, which protects the nose and oral mucosa, is mainly protected by wearing masks to prevent the new coronavirus, but the conjunctiva exposed to the environment is easily overlooked.
The results of this study suggest that exposed mucous membranes and unprotected eyes increase the risk of SARS virus or neo-coronavirus infection, which means that, especially for clinicians, it is necessary to raise awareness of eye protection when coming into contact with patients or in places where there are many people, wash our hands regularly in our daily lives and wear protective glasses.
‘We can only effectively stop the spread of COVID-19 by cutting off all transmission of the new coronavirus,’ the researchers concluded.