Can COVID-19 be transmitted through the conjunctiva of the eye? On March 14, local time, bioRxiv, a bioscience preprinted platform, published a new study on the spread of new coronavirus disease (COVID-19) through the ocular conjunctival pathway. conjunctival route. "
The Qinchuan team of the Institute of Medical Laboratory Animals, Chinese Academy of Medical Sciences has found for the first time that COVID-19 can be transmitted through the conjunctival pathway, that is, rhesus monkeys can effectively infect COVID-19 through the ocular conjunctival pathway. This is a virus prevention, especially for medical personnel. Protection provides important theoretical support.
Based on clinical symptoms, viral load testing, and serological examinations, the authors found that rhesus monkeys can be infected with COVID-19 through the conjunctival pathway, and that the virus will migrate from the conjunctiva to the respiratory tract and other tissues one day after infection.
The authors of the study are from the Institute of Medical Laboratory Animals, Chinese Academy of Medical Sciences and Beijing Anzhen Hospital, Capital Medical University. The corresponding author is Qin Chuan, director of the Institute of Medical Laboratory Animals, Chinese Academy of Medical Sciences, and special allowance expert of the State Council. As an expert in comparative medicine and pathology, Qin Chuan was responsible for participating in the "establishment of animal models of SARS infection" in 2003. In addition, he led the team to conduct experiments on animal models of various infectious diseases.
The outbreak of COVID-19 is highly contagious. At present, it is generally believed that COVID-19 is mainly transmitted through respiratory droplets or direct close contact between people, but other potential routes of transmission remain to be further studied.
In previous clinical cases, conjunctivitis patients with SARS (Severe Acute Respiratory Syndrome) and COVID-19 had detected viral RNA in tears and conjunctival secretion samples.
Previously, Wang Guangfa, a member of the expert group of the National Health Commission and the director of the Department of Respiratory and Critical Care Medicine, Peking University First Hospital, went to work in Wuhan and was diagnosed with COVID-19 infection. He also speculated that the route of his infection might be that the virus first entered the conjunctiva. And then to the whole body.
However, at the same time, the research team of the Chen Changzheng team of the People's Hospital of Wuhan University also stated that COVID-19 can be detected in the conjunctival sac of patients with new coronary pneumonia, but clinical analysis data does not support the transmission of COVID-19 through the conjunctival route.
In the latest study, researchers inoculated a certain half of the tissue culture infection dose (TCID50) of COVID-19 to three 3 to 5 year-old rhesus macaques, and randomly selected two for conjunctival vaccination. The other one was vaccinated by intratracheal injection to compare the virus distribution and pathogenesis of hosts infected with COVID-19 through different routes. The researchers only inoculated the rhesus monkeys with a single route to ensure their exact route of infection.
Researchers observed the clinical signs of rhesus monkeys daily and found that there were no significant clinical changes in body weight and temperature of rhesus monkeys infected with the virus through two routes. The research team collected routine specimens, including nasal and throat swabs, at 0, 1, 3, 5 and 7 days (dpi) after vaccination.
In addition, the research team also collected conjunctival swabs and anal swabs from rhesus monkeys to explore potential routes of COVID-19 excretion in the host.
It is worth noting that the researchers were able to detect viral load in conjunctival swabs of rhesus monkeys infected by the ocular conjunctival route on the first day after vaccination, but then they could no longer detect the virus in the conjunctiva. The research team believes that this means that inoculated COVID-19 may migrate from the conjunctiva to the respiratory tract and other tissues.
Viral loads were continuously detected in the nasal and throat swabs of the three rhesus monkeys 1 to 7 days after vaccination.
In addition, specific IgG antibodies against COVID-19 could still be detected in two rhesus monkeys after 14 and 21 days of conjunctival vaccination with COVID-19, suggesting that they were indeed infected with COVID-19.
For anal swabs, although no viral load was detected in conjunctival virus-inoculated rhesus monkeys, it was continuously detected in rhesus monkey specimens inoculated by the intratracheal route.
Seven days after the virus inoculation, the researchers euthanized and performed an autopsy on the trachea-inoculated rhesus monkey and one of the conjunctiva-inoculated rhesus monkeys.
For conjunctiva-inoculated rhesus monkeys, the viral load is mainly distributed in: the nasolacrimal duct system and the eye, including the lacrimal gland, optic nerve, and conjunctival nasal cavity; the nose, including the nasal mucosa, turbinate, and nostril; Jawbone and trachea; in the mouth, including examination bags and parotid glands; and other tissues, including the left lower lobe of the lung, groin and pararectum (lymph nodes), stomach, duodenum, cecum and ileum.
Study confirms that COVID-19 can be transferred to the respiratory tract after ocular conjunctival infection
Viral load on ocular conjunctival, nasal, laryngeal, and anal swab specimens of three rhesus monkeys inoculated at 0, 1, 3, 5, and 7 days after inoculation, C-1 and C-2 represent the conjunctival route to inoculate the virus Of two rhesus monkeys, IT-1 is an intratracheal inoculated rhesus monkey
In contrast, the distribution of viruses in rhesus monkeys that were inoculated intratracheally was different. Viral replication occurs mainly in the lungs, and viral load is also high in the nasal septum, trachea, mandibular lymph nodes, tonsils, pulmonary lymph nodes, and some segments of the digestive tract (including the cecum, colon, duodenum, and jejunum).
Notably, researchers could detect the virus in different parts of the rhesus monkey's digestive tract, suggesting that the digestive system may be susceptible to COVID-19 infection.
Compared with rhesus monkeys that were inoculated by the intratracheal route, the viral load and distribution in conjunctivally infected rhesus monkeys is relatively high in the nasolacrimal system, but relatively light and local in the lungs. However, both of these pathways can cause digestive tract infections.
The results of these experiments indicate that the conjunctiva is the gateway for COVID-19 transmission. Researchers were able to detect viral load in several related tissues of the nasolacrimal system, especially in the conjunctiva, lacrimal glands, nasal cavity, and throat, which serve as a "bridge" for viral movement between the eye and respiratory tissues.
It is worth noting that the lacrimal duct, as a conduit for collecting and transporting tear fluid from the surface of the eye to the lower nasal passage, also facilitates the drainage of the virus from the eye tissue to the respiratory tract tissue.
In fact, previous reports have shown that, although the conjunctiva, sclera, or cornea can absorb virus-containing fluids, most fluids, including tears and secretions, are expelled into the nasopharynx or swallowed. Lacrimal epithelium may also help with tear absorption.
The results are also highly consistent with the anatomical characteristics of the virus entering the host via the conjunctival pathway. Researchers say that people currently prevent COVID-19 by wearing a mask. This method mainly protects the nasal and oral mucosa, but the conjunctiva exposed to the environment is easily ignored.
The results of this study indicate that exposed mucous membranes and unprotected eyes increase the risk of SARS virus or COVID-19 infection, which means that, especially for clinicians, when in contact with patients or in crowded places At times, it is necessary to raise awareness of eye protection, wash hands regularly and wear protective glasses in daily life.
The researchers wrote at the end of the article that only by cutting off all transmission methods of COVID-19 can we effectively prevent the transmission of COVID-19.
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