SARS-CoV–2 is a single-stranded positive-strand RNA virus, and the known acute respiratory syndrome coronavirus (SARS-CoV) and the Middle East respiratory syndrome coronavirus (MERS-CoV) belong to the β-coronavirus genus . Although SARS-CoV–2 is less pathogenic than SARS-CoV and MERS-CoV, the population is generally susceptible, and confirmed cases have been reported in more than 70 countries in the world. The common clinical manifestations of patients with COVID–19 are fever, dry cough, and fatigue, and a few patients may have digestive symptoms such as vomiting and diarrhea . The underlying disease and elderly patients are more severe, and severe cases can quickly progress to acute respiratory distress syndrome, septic shock, and multiple organ failure . Asymptomatic infections have no obvious clinical symptoms and signs and are difficult to detect. Recent studies have shown that a large number of infections occur in patients before the symptoms of COVID–19, suggesting that asymptomatic infections may be contagious [10–12]. In this case, the patient had fever on February 4th, and the body temperature returned to normal after oral administration of cold drug, which does not exclude that the fever at that time was caused by SARS-CoV–2 infection. Her uncle suffered fever, sore throat, and cough. was diagnosed SARS-CoV–2 nucleic acid positive on February 22 at a fever clinic in Beijing China-Japan Hospital. Fortunately, the patient was discovered during the epidemiological investigation of her uncle by the epidemic prevention staff, and the patient did not complain when she was admitted to the hospital.
Nucleic acid testing is the “gold standard” for patients diagnosed with COVID–19. Throat swabs, sputum and other respiratory secretions, blood, feces, etc. can be used as samples for SARS-CoV–2 nucleic acid detection, but they are susceptible to the course of the patient, the location of the material, and the type of material. Some patients are positive after multiple nucleic acid tests. Therefore, there may be false negatives in nucleic acid detection. Chest CT is the primary means of assessing the condition of suspected and confirmed COVID–19 patients, but imaging findings may be delayed and need to be distinguished from other viral pneumonias. This patient was found in the epidemiological investigation of confirmed cases. On February 23, her throat swab was positive for nucleic acid test (outer hospital), and chest CT (outer hospital) showed no obvious abnormalities. She was admitted to our hospital for isolation and treatment on February 24, and the tests showed that her urine nucleic acid was positive, but her throat swab was negative. On February 26, her throat swab was positive for nucleic acid, considering the false negative of throat swab on February 24. Her HRCT presented small nodules in the anterior outer basal segment of the left lower lobe (Fig. 1c), which our team considering nothing to do with novel coronavirus pneumonia. In this case, the throat swab and urine nucleic acid tested positive, and there were no clinical symptoms and changes in imaging of viral pneumonia. The family members (uncle) in close contact were diagnosed, and her mother and brother were also diagnosed asymptomatic infection (negative urine nucleic acid), so she was considered to be a family-clustered asymptomatic infection. On March 3 and 5, the patient was reviewed and her throat swab and urine nucleic acid were negative, and no complaints were reported. On March 9 and 12, her throat swab nucleic acid were negative. The patient was discharged from the hospital on March 13 and continued to be isolated and observed outside the hospital. Follow-up was conducted on March 26, the patient did not have any discomfort, the throat swab nucleic acid test was negative, and the isolation was lifted.
Based on current epidemiological data, COVID–19 is mainly transmitted through droplets and close contact . Although live SARS-CoV–2 has been isolated from feces, there is no evidence as to whether it can be transmitted through the fecal-oral route . Previous studies have shown that MERS-CoV has fecal-oral transmission characteristics . In this case, the patient was positive for urine nucleic acid when she was admitted to the hospital, suggesting that the patient may excrete the virus and may become a source of infection. According to the latest COVID–19 diagnosis and treatment guidelines in China, the diagnosis can be confirmed as long as the nucleic acid test is positive. Compared with nasopharyngeal swab and sputum specimens, feces and urine sampling is more convenient, and the quantity and quality of specimens are easily satisfied. Increasing their detection may increase the detection rate of asymptomatic infection.
Among major infectious diseases, asymptomatic infection has very important epidemiological significance (such as acquired immune deficiency syndrome, tuberculosis) [14, 15]. Asymptomatic patients with SARS-CoV–2 infection have no clinical symptoms or even biochemical changes, so they are mainly found through clustered epidemiological investigation and infectious disease source follow-up investigation. Asymptomatic infection should attract the attention of health administrative departments and researchers. Understanding and grasping the situation of asymptomatic infection not only facilitates the monitoring of the patient’s condition, but also facilitates the establishment of a virus model to understand its scope and spread. At the same time, it should also be noted that whether asymptomatic infection can be transmitted through droplets and contact, and whether excreta (urine, feces, vomit, etc.) can be transmitted from person to person through contamination of water, food and the environment, it should be the control focus of epidemic prevention. The public should reduce going out, or wearing of masks when going out, put an end to crowd gathering, wash hands frequently. Taking a good job of disinfection and other correct protective measures are effective means to prevent infection.
COVID–19 can be present in asymptomatic individuals, and their urine may be one of the sources of infection.