SARS-CoV-2 is a viral disease that is transmitted by different mechanisms, among which are aerosols and fomites. The stethoscope is a medical device that is used for different patients, which is known for its ability to transmit other infectious diseases between patients and healthcare workers.1,2 Usually, the stethoscope is placed on the front and back of the chest, while the patient breathes or even coughs on it. Despite the exponential growth of knowledge about the infection by SARS-CoV-2, to date, no study has been published that analyzes the possibility that the stethoscope acts as a fomite in the transmission of SARS-CoV-2. We conducted the present study to assess the ability of transmitting SARS-CoV-2 through the stethoscope.
In our hospital, a clean stethoscope was placed in each isolation room with symptomatic patients with pneumonia due to SARS-CoV-2. During the months of January and February 2021, we studied the presence of SARS-CoV-2 in 100 stethoscopes from specific SARS-CoV-2 rooms. Two hours after conducting the respiratory assessment, samples for PCR detection of SARS-CoV-2 RNA were taken using a swab with a synthetic tip and a plastic shaft rubbing the diaphragm for 10s. A real-time Seegene PCR that detected 3 specific genes (RdRP, E and N) was used. The stethoscopes were not disinfected since the first day of admission of the patients. Fifty-four of them were in single rooms, and the remaining in double rooms. The patients admitted to these rooms had a median hospital stay prior to inclusion in the study of 7 days (3–12). The presence of SARS-CoV-2 was confirmed with nasopharyngeal swabs on the day of admission. PCR was used in 75 of the cases, with a mean cycle threshold (Ct) of 26±5.1. The remaining 71 were confirmed by antigen detection by chemiluminescence, which could be a limitation of the study. SARS-CoV-2 RNA was not detected in any of the samples obtained from the stethoscopes.
Despite the importance of standard precautions, such as environmental cleaning and hand hygiene, which prevent the transmission of other microorganisms, the demonstration that a single route of transmission is capable of transmitting SARS-CoV-2 in real situations is very complex. The most studied and known SARS-CoV-2 transmission mechanism is produced by drops, caused by direct, indirect or close contact with infected people through the contaminated secretions expelled during speech (5–10μm). Airborne transmission caused by the suspension of aerosols in the air for long periods, especially in closed environments with poor ventilation (<5μm), has also been stablished.3 The last studied mechanism, transmission by fomites, is caused by respiratory secretions deposited on different surfaces and objects, which can be maintained for long periods (from hours to days), depending on the type of surface, especially in hospital environments. This fact has motivated the performance of various studies that consider the possibility of this route of transmission plausible, especially in rooms of patients infected by SARS-CoV-2. The virus is more stable in plastic and steel (stethoscope materials) than in copper and cardboard, and viable virus remains can be detected up to 72h later, with stability kinetics like SARS-CoV-1.4 Environmental contamination has been described in rooms with symptomatic patients with SARS-CoV-2 infection, being more frequent on the floor and bed rail, associated with a lower cycle threshold and during the first week of admission. This is probably due to direct contamination by either the patient or by healthcare workers after contacting with infected respiratory fluids.5 There are controversial studies that describe the presence of SARS-CoV-2 RNA in the hospital environment, but none of them has shown it as the cause of an outbreak.6,7 Our study revealed that, despite including symptomatic patients with low Ct, the presence of SARS-CoV-2 on stethoscopes was not found.
In conclusion, the stethoscope as a medical tool that is in contact with the patient is not a fomite capable of transmitting SARS-CoV-2 but this fact does not mean that systematic cleaning should not be performed.
FundingThe PCR reagents used were provided by Werfen Werfen (Spain).
Conflicts of interestNone to declare.
