key: cord-271211-frkk6w0a authors: Han, Yu; Yang, Hailan title: The transmission and diagnosis of 2019 novel coronavirus infection disease (COVID‐19): A Chinese perspective date: 2020-03-12 journal: J Med Virol DOI: 10.1002/jmv.25749 sha: doc_id: 271211 cord_uid: frkk6w0a 2019 novel coronavirus (SARS‐CoV‐2), which originated in Wuhan, China, has attracted the world's attention over the last month. The Chinese government has taken emergency measures to control the outbreak and has undertaken initial steps in the diagnosis and treatment of 2019 novel coronavirus infection disease (COVID‐19). However, SARS‐CoV‐2 possesses powerful pathogenicity as well as transmissibility and still holds many mysteries that are yet to be solved, such as whether the virus can be transmitted by asymptomatic patients or by mothers to their infants. Our research presents selected available cases of COVID‐19 in China to better understand the transmission and diagnosis regarding this infectious disease. both of them did not wear masks. 5 SARS-CoV-2 possesses powerful pathogenicity and transmissibility, being more infectious than SARS-CoV and MERS-CoV. 6 Encountering a confirmed patient and being close for 15 or 50 seconds is not the only route of infection, though it is the most likely route in the above two cases. Moreover, being infected within a very short exposure time is possible in the absence of masks. 7 The powerful infectivity of SARS-CoV-2 may be explained by the latest findings reported by Wrapp D et al, 8 which showed that the SARS-CoV-2 S binds to angiotensin-converting enzyme 2 (ACE2) receptors with a higher affinity than SARS-CoV S. Another underlying reason was reported by Zou L et al 9 in that the shedding pattern of viral nucleic acid in patients infected with SARS-CoV-2 is similar to that in patients with influenza and appears to be different from that in patients infected with SARS-CoV. SARS-CoV-2 often causes cluster transmission, especially within family clusters. In some cities, cases involving cluster transmission accounted for 50% to 80% of all confirmed cases of COVID-19. 10 Human-to-human transmission of SARS-CoV and MERS-CoV occurred mainly through nosocomial transmission, and transmission between family members only occurred in 13% to 21% of MERS cases and 22% to 39% of SARS cases. 11 SARS-CoV-2 can be transmitted by droplets and contact. A study in South Korea showed that many environmental surfaces of patients with MERS were contaminated by MERS-CoV, and virus RNA was detected from environmental surfaces within 5 days after the last positive PCR of patients' respiratory samples. 12 Guangzhou CDC also found SARS-CoV-2 in the house of a confirmed patient, 13 which serves as evidence of contact transmission. Moreover, live viruses have been found in the feces of patients with COVID-19, 14 however, the fecal-oral transmission of the virus has not been shown. Studies have shown that SARS-CoV may be detected in the feces of most SARS patients, 15 and the virus within feces could survive at room temperature for at least 1 to 2 days. 16 It is possible but infrequent for SARS-CoV to spread via the fecal-oral route. 17 In patients with MERS, feces and urine samples also yielded viral RNA. 18 Given the evidence of fecal contamination of SARS-CoV and MERS-CoV as well as their ability to survive in feces, it is possible that SARS-CoV-2 may also be transmitted through the fecal-oral route. 19 Additionally, in regard to the expression of ACE2 in the intestine and kidney, SARS-CoV-2 may infect these tissues and enter the feces, allowing its potential spread via fecal-oral route. 20 The Lancet also reminded doctors not to ignore SARS-CoV-2 transmission via ocular surfaces as infected droplets and bodily fluids may easily contaminate the human conjunctival epithelium. 21 Guangfa Wang, a member of the National Health Commission of the People's Republic of China (NHC) expert panel on pneumonia, was exposed to a fever clinic in Wuhan with only his eyes unprotected. He then demonstrated symptoms of conjunctivitis in his left lower eyelid 2 days before the onset of COVID-19. 22 On February 19, the NHC published the 6th edition of Guideline on diagnosis and treatment of COVID-19 (the 6th Guideline for COVID -19) . 23 This document asserted that the transmission of SARS-CoV-2 mainly occurs via large droplets and contact. Additionally, the virus may spread in an unventilated environment with high levels of viral aerosols. In addition, researchers claimed the spread of SARS-CoV-2 could be characterized by super-spreading events. 24 However, there is no evidence of super-spreading events in any medical institution that treats patients suffering from COVID-19. 6 And a study in South Korea showed that for transmission of MERS-CoV nonisolated in-hospital days was the only factor which tended to be higher in super-spreaders than usual-spreaders. 25 Therefore, whether there are super-spreaders or not, early isolation is necessary to reduce the size of the outbreak of SARS-CoV-2. Over the past few days, asymptomatic patients were found in many Chinese cities. Table 1 outlines its summary. T A B L E 1 Summary of asymptomatic patients Wuhan were confirmed to have COVID-19 after returning to Shenzhen, with their asymptomatic child presenting with no fever, respiratory tract symptoms or diarrhoea but had ground-glass lung opacities seen on radiography. 26 Subsequently, asymptomatic patients were discovered in many Chinese cities with most of them having an epidemiological history. Asymptomatic infections may occur due to weakened immune responses and subclinical manifestations, or because the virus is waiting for opportunities to reproduce and invade. To understand its mechanism requires additional investigation of asymptomatic patients as well as blood tests pointing to signs of an immune response, which can help detect asymptomatic or presymptomatic cases. 27 A study showed that during the outbreak of SARS-CoV, of all exposed health care workers, 7.5% were asymptomatic SARSpositive cases. Asymptomatic SARS was associated with lower SARS antibody titers and a higher use of masks compared to that of pneumonic SARS. 28 Another study showed that of 255 patients with laboratory-confirmed MERS-CoV, a total of 64 patients (25.1%) were reported to be asymptomatic. However, 33 (52%) of the 64 patients were interviewed with 26 (79%) of them having reported at least one respiratory symptom. 29 This phenomenon indicates whether asymptomatic patients were actually infected without showing symptoms. Whether asymptomatic people can transmit SARS-CoV-2 to others is unclear. The 6th Guide for COVID-19 noted that asymptomatic patients may serve as a source of infection. An article in NEJM first reported a German to be confirmed with COVID-19 after contact with an asymptomatic Chinese patient. 30 However, it turned out that the Chinese patient had a fever in Germany and took antipyretics. A recent study in NEJM reported that a viral load detected in an asymptomatic patient was similar to that detected in symptomatic patients, indicating the potential for transmission in asymptomatic patients. 9 Table 1 indicates that these asymptomatic patients may infect others or develop symptoms later, but the number of patients involved is small. We remind readers to take this into account when interpreting the research results and conclusions as some of the above observations may be accidental. Another uncertainty is whether those who are asymptomatic can cause large-scale infections. A study in South Korea showed that during the MERS outbreak in Korea, an asymptomatic patient with MERS was discovered, and none of the 82 persons exposed to that patient without protection was infected. 31 Most of the asymptomatic patients had close contact with confirmed patients, hence, they may be isolated in a timely manner when tracking close contacts. Moreover, the number of asymptomatic patients was very small; according to epidemiological data in mainland China, only 1.2% of patients with COVID-19 are asymptomatic. 6 Due to the above reasons, such patients will generally not cause large-scale transmissions of SARS-CoV-2. 32 February 2, was delivered by a mother who was confirmed to have COVID-19. The cord blood and placental tissue were collected immediately and tested negative for SARS-CoV-2, but nasopharyngeal swab samples collected 36 hours after birth were positive. 33 SARS-CoV-2 is a novel virus and shares a 79.0% nucleotide identity with the sequence of SARS-CoV and a 51.8% identity with that of MERS-CoV. 34 The alveolar lavage test is the best way to confirm SARS-CoV-2, however, the detection of alveolar lavage fluid is mostly used in severe patients using an invasive ventilator. Sputum is considered the second choice, though the coughs of many patients with COVID-19 are unproductive. 46 Therefore, pharyngeal swabs are the most common sampling method, however, they may occasionally cause missed diagnoses for smaller levels of SARS-CoV-2 residing in the pharynx. In addition, PCR detection takes up a lot of time, hampering the control of infectious diseases. Therefore, the Revised Version of the 5th edition added clinical confirmed standards for the Hubei Province. 47 Genomic characterization of the 2019 novel human-pathogenic coronavirus isolated from a patient with atypical pneumonia after visiting Wuhan A man was infected by contacting with a confirmed patient for 15 seconds without a mask A man was infected by contacting with a confirmed patient for 50 seconds without a mask Novel Coronavirus Pneumonia Emergency Response Epidemiology Team Central People's Government of the People's Republic of China. 14 key questions and answers Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation SARS-CoV-2 viral load in upper respiratory specimens of infected patients Special Expert Group for Control of the Epidemic of Novel Coronavirus Pneumonia of the Chinese Preventive Medicine Association SARS and other coronaviruses as causes of pneumonia Environmental contamination and viral shedding in MERS patients during MERS-CoV Outbreak in South Korea Nanfang Metropolis Daily. 2019-nCoV was found in the house of the confirmed patient Information Office People's Government of Guangdong Province. 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