Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), classified as family Coronaviridae and genus Betacoronavirus,¹ is widely known to be transmitted by respiratory droplets and close contact. However, other possible mechanisms of transmission have been concerned scientific community, as by airborne, bloodborne, intrauterine, oral‐fecal, breastfeeding, and other modes of transmission.² The presence of this virus was observed in other human materials than oropharyngeal swabs as urine, feces, anal swabs, blood specimens, and saliva, indicating that SARS‐CoV‐2 can infect multiple systems,³ although the role of these materials in transmission remains unclear. Respiratory droplets (>5–10 μm in diameter) which contain viable virus are expelled by infected people when cough, sneeze, or talk. This transmission occurs when a susceptible person is in close contact (within 1 meter).² However, airborne transmission is still in debate, since aerosols (<5 μm in diameter) can transmit SARS‐CoV‐2 during medical procedures that generate aerosols.² But other questions as if aerosol can transmit SARS‐CoV‐2 in indoor settings with poor ventilation in the absence of aerosol‐generating procedures only in the presence of aerosol exhaled by people, if aerosols contain viable virus in sufficient quantity to cause infection, are still not answered. Since measures to prevent transmission are the bases to control the pandemic, this letter intends to report a case of SARS‐CoV‐2 virus in the urine of an asymptomatic patient and to alert about handling urine samples as potential biohazardous, due aerosol formation.

A male, 53‐year‐old, dentist, noticed that his urine seemed to have blood. A regular urine test was performed which presented 200,000 blood cells/ml and showed that the kidneys had a normal renal function, as well as on imaging exams (ultrasound and tomography), no changes were noted, except for a few hepatic steatoses. To investigate the possibility of atypically COVID‐19 symptoms, since it was a case of undiagnosed hematuria, a urine sample was collected. Also, throat wash sample was collected, after gargling with 3 ml of saline, as standardized in our laboratory in substitution of the swab. All procedures were in accordance with the ethical standards and the patient signed the consent form. We performed RNA extraction by silica column (Biogene, Brazil) and five reverse transcription‐polymerase chain reaction (RT‐PCR) runs for each biological sample with two different protocols. In three runs the target was the E gene, according to Charite protocol,⁴ using a kit from Biomanguinhos, Brazil, and in two runs the target were N1 and N2 genes, according to CDC protocol,⁵ using a kit from IDT, USA. For all RT‐PCR run, it was also performed another run to evaluate the presence of the human RNase P gene (RP), used as nucleic acid extraction control. A specimen was considered positive, as specified for the manufacturer, when the cycle threshold (CT) was less than 37 (for E gene ‐ Biomanguinhos) and less than 40 (for N1 or N2 genes ‐ IDT).

As a result of RT‐PCR, we observed some positive reactions with a high CT. For the throat wash sample, no gene was detected, except for the RP gene. For urine, the E gene was detected in two of three attempts, with CT 37, 0, and 34 (Figure 1). The N1 gene was not detected in the only one attempt, but N2 was detected, with CT 38 (Figure 1). All run performed to detected gene RP was positive (data not shown). Our results indicate the presence of SARS‐CoV‐2 in urine, probably in low viral concentration, due to the high CT and some negative reactions. Possibly he was in a last stage of infection since a low viral load was found in urine and there was no detection in the throat wash sample. Since two different genes were detected, despite the use of different protocols and higher CT observed, we agreed that the final result of this patient was positive for SARS‐CoV‐2.

The results here presented, as other works in literature, proved that is possible to detect SARS‐CoV‐2 in the urine of an asymptomatic patient. This indicates that probably it will be more often found this virus in urine in other patients, even in the absence of specific symptoms. Thus, it is important to consider urine as a potential biohazard material during SARS‐CoV‐2 pandemic time. In diagnostic laboratories, urine is manipulated at the bench, centrifuged and homogenized for urinalysis. Since these procedures can generate aerosol and no special personal protective equipment besides gloves and lab coat are worn by health workers, it is suggested that some precautions measures should be taken. It is important to consider that, at this moment, all urine samples should be manipulated in biological safety cabinet class II, and centrifugation should be performed in a containment device for health workers protection, which can be infected and increase the spread of this virus. However, it is known that these procedures can be expensive for a typically low‐cost assay, and probably many laboratories in poor countries do not have these facilities. Thus, other measures should be taken to avoid air contamination. Also, it arises concerns about surgical interventions in the urinary tract, when physicians can be infected during the procedure. So, it was suggested that urine from patients should be tested in priory.⁶ And maybe, we can add that it should be considered higher CT as positive results when RT‐PCR is performed for urine samples.

Moreover, when it takes into account that urine can produce aerosol when it is expelled, other concerns can be raised. Is that possible to be infected when using public restrooms, simply by inhaling the air? Can flush the toilet be hazardous due to aerosol formation, especially in places with a great flow of people as shopping malls or schools? Our laboratory has performed air monitoring, not surface, in different areas of our center, as offices, cafeteria, restrooms, and all laboratory rooms, including where samples of COVID‐19 subjects were manipulated. We only detected the presence of the SARS‐CoV‐2 virus in the air of the cafeteria and one of four restrooms (unpublished observations). This indicates we were able to contain the virus during laboratory procedures, however it suggests that indoor and inadequately ventilated spaces are not safe. As observed in others works, that showed the presence of SARS‐CoV‐2 in air samples in different places, medical or nonmedical facilities, where there are no aerosol‐generating procedures.² So, it was suggested that aerosol formation was due to symptomatic COVID‐19 patients or asymptomatic carriers of the virus during breathing or talking, but the role of aerosols in transmission still needs further studies. Besides, RT‐PCR detects only the presence of RNA, which is not indicative of the presence of viable virus that could be capable of causing infection.² Thus, if urine can contaminate the restrooms' air with viable virus capable to cause infection, it is still uncertain, but maybe precautions should be taken, and not wear a mask can be dangerous.

It is worthy to add that, in time of SARS‐CoV‐2 pandemic, clinicians must consider suspecting of COVID‐19 in patients with urology issues, even if respiratory symptoms were not observed. In this case, they can collect urine in the early or middle stage of infection and the laboratory diagnosis can be more precise.

严重急性呼吸综合征冠状病毒2（SARS-CoV的-2），分类为家族冠状和属乙型，¹是公知的由飞沫和密切接触来传送。然而，其他可能的传播机制也受到了科学界的关注，例如通过空气传播，血液传播，子宫内，粪便，母乳喂养和其他传播方式。²在口咽拭子以外的其他人类物质中，例如尿液，粪便，肛门拭子，血液标本和唾液中也观察到该病毒的存在，这表明SARS-CoV-2可以感染多个系统，³尽管这些材料在传播中的作用尚不清楚。感染的人在咳嗽，打喷嚏或说话时会排出含有活病毒的呼吸飞沫（直径> 5–10μm）。当易感人群紧密接触（1米以内）时，就会发生这种传播。²然而，空中传播仍在争论中，因为气溶胶（直径<5μm）可以在产生气溶胶的医疗程序中传播SARS-CoV-2。²但是还有其他一些问题，例如如果气雾剂中含有足以引起感染的活病毒，那么只有在人们呼出的气雾剂存在下，如果没有气雾剂生成程序，气雾剂就能在室内通风不佳的室内环境中传播SARS-CoV-2。仍然没有回答。由于预防传播的措施是控制大流行的基础，因此该信旨在报告无症状患者尿液中的SARS-CoV-2病毒病例，并提醒您注意将尿液样品视为潜在的生物危害性烟雾形成物。

一名53岁的男性牙医发现他的尿液似乎有血液。进行了常规尿液检查，结果为200,000血细胞/ ml，表明肾脏的肾脏功能正常，以及影像学检查（超声和断层扫描），除少数肝脂肪变性外，未见变化。为了调查非典型COVID-19症状的可能性，由于这是一种未确诊的血尿，因此收集了尿液样本。同样，在用3 ml盐水漱口后，收集喉咙清洗样品，按照我们实验室的标准，以代替拭子。所有程序均符合道德标准，患者签署了同意书。我们通过硅胶柱（Biogene，巴西）和五个逆转录聚合酶链反应（RT-PCR），每种生物样品都有两种不同的操作流程。根据Charite协议，在三轮中目标是E基因，⁴使用来自巴西Biomanguinhos的试剂盒，在两次运行中，根据CDC协议，靶标分别是N1和N2基因， ⁵使用美国IDT的试剂盒。对于所有RT-PCR运行，还进行了另一次运行以评估用作核酸提取对照的人RNase P基因（RP）的存在。当周期阈值（CT）小于37（对于E基因-Biomanguinhos）和小于40（对于N1或N2基因-IDT）时，按照制造商的要求，将标本视为阳性。

RT-PCR的结果是，我们观察到一些高CT阳性反应。对于喉咙清洗样品，除了RP基因外，没有检测到任何基因。对于尿液，在三次尝试中有两次尝试检测到了E基因，CT为37、0和34（图1）。仅在一次尝试中未检测到N1基因，但在CT 38中检测到了N2（图1）。对检测到的基因RP进行的所有运行均为阳性（数据未显示）。我们的结果表明，由于高CT和一些不良反应，尿液中可能存在低病毒浓度的SARS-CoV-2。由于尿液中发现病毒载量低，并且在洗喉样品中未检测到病毒，因此他可能处于感染的最后阶段。由于检测到两个不同的基因，尽管使用了不同的方案并观察到了更高的CT，

与其他文献一样，此处给出的结果证明可以检测到无症状患者尿液中的SARS-CoV-2。这表明即使在没有特定症状的情况下，在其他患者的尿液中也可能会更频繁地发现这种病毒。因此，重要的是在SARS-CoV-2大流行期间将尿液视为潜在的生物危害物质。在诊断实验室中，在工作台上对尿液进行处理，离心并匀浆以进行尿液分析。由于这些程序会产生气溶胶，并且卫生工作者除了戴手套和穿实验服外也没有特殊的个人防护设备，因此建议采取一些预防措施。重要的是要考虑到，此时，所有尿液样本都应在II级生物安全柜中进行处理，并应在封闭装置中进行离心，以保护卫生工作者，该装置可能被感染并增加了这种病毒的传播。但是，众所周知，对于通常的低成本测定而言，这些程序可能会很昂贵，并且贫穷国家的许多实验室可能没有这些设施。因此，应采取其他措施避免空气污染。同样，当医生在手术过程中可能被感染时，也会引起对泌尿道外科手术干预的关注。因此，建议应事先对患者尿液进行检查。贫穷国家的许多实验室可能没有这些设施。因此，应采取其他措施避免空气污染。同样，当医生在手术过程中可能被感染时，也会引起对泌尿道外科手术干预的关注。因此，建议应事先对患者尿液进行检查。贫穷国家的许多实验室可能没有这些设施。因此，应采取其他措施避免空气污染。同样，当医生在手术过程中可能被感染时，也会引起对泌尿道外科手术干预的关注。因此，建议应事先对患者尿液进行检查。⁶也许我们可以补充一点，当对尿液样本进行RT-PCR时，应将CT视为阳性。

此外，如果考虑到尿液在排出时会产生气溶胶，则可能引起其他问题。使用公共洗手间时，仅通过吸入空气就能感染这种病毒吗？抽水马桶是否会因形成烟雾而有害，尤其是在购物中心或学校等人流密集的地方？我们的实验室在我们中心的不同区域（如办公室，自助餐厅，洗手间和所有实验室）（包括操作COVID-19受试者的样品）进行了空气监测，而不是表面监测。我们仅在自助餐厅和四个洗手间之一的空气中检测到SARS-CoV-2病毒的存在（未发表的观察结果）。这表明我们能够在实验室程序中控制该病毒，但是这表明室内和通风不良的空间并不安全。²因此，有人认为气溶胶的形成是由于有症状的COVID-19患者或在呼吸或说话过程中无症状的病毒携带者，但气溶胶在传播中的作用仍需进一步研究。此外，RT-PCR仅检测RNA的存在，这并不表示可能会引起感染的活病毒的存在。²因此，如果尿液能被能够感染的活病毒污染厕所空气，仍是不确定的，但也许应采取预防措施，不戴口罩会很危险。

值得补充的是，在SARS-CoV-2大流行期间，即使没有观察到呼吸道症状，临床医生也必须考虑在泌尿科问题患者中怀疑COVID-19。在这种情况下，他们可以在感染的早期或中期收集尿液，并且实验室诊断可以更加精确。