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CDC: covid-19 transfers via air and shoes

This is a new CDC study. It shows aerosol spread of the Corona Virus and spread on the shoes of caregivers.


Aerosol and Surface Distribution of Severe Acute Respiratory Syndrome Coronavirus 2 in Hospital Wards, Wuhan, China, 2020


https://wwwnc.cdc.gov/eid/article/26/7/20-0885_article 


These are excepts from the article:


We further assessed the risk for aerosol transmission of SARS-CoV-2. First, we collected air in the isolation ward of the ICU (12 air supplies and 16 air discharges per hour) and GW (8 air supplies and 12 air discharges per hour) and obtained positive test results for 35% (14 samples positive/40 samples tested) of ICU samples and 12.5% (2/16) of GW samples. Air outlet swab samples also yielded positive test results, with positive rates of 66.7% (8/12) for ICUs and 8.3% (1/12) for GWs. These results confirm that SARS-CoV-2 aerosol exposure poses risks. 


Furthermore, we found that rates of positivity differed by air sampling site, which reflects the distribution of virus-laden aerosols in the wards (Figure 2, panel A). Sampling sites were located near the air outlets (site 1), in patients’ rooms (site 2), and (site 3). SARS-CoV-2 aerosol was detected at all 3 sampling sites; rates of positivity were 35.7% (5/14) near air outlets, 44.4% (8/18) in patients’ rooms, and 12.5% (1/8) in the doctors’ office area. These findings indicate that virus-laden aerosols were mainly concentrated near and downstream from the patients. However, exposure risk was also present in the upstream area; on the basis of the positive detection result from site 3, the maximum transmission distance of SARS-CoV-2 aerosol might be 4 m. According to the aerosol monitoring results, we divided ICU workplaces into high-risk and low-risk areas (Figure 2, panel B). The high-risk area was the patient care and treatment area, where rate of positivity was 40.6% (13/32). The low-risk area was the doctors’ office area, where rate of positivity was 12.5% (1/8).


Furthermore, half of the samples from the soles of the ICU medical staff shoes tested positive. Therefore, the soles of medical staff shoes might function as carriers. The 3 weak positive results from the floor of dressing room 4 might also arise from these carriers. We highly recommend that persons disinfect shoe soles before walking out of wards containing COVID-19 patients.


This study led to 3 conclusions. First, SARS-CoV-2 was widely distributed in the air and on object surfaces in both the ICU and GW, implying a potentially high infection risk for medical staff and other close contacts. Second, the environmental contamination was greater in the ICU than in the GW; thus, stricter protective measures should be taken by medical staff working in the ICU. Third, the SARS-CoV-2 aerosol distribution characteristics in the GW indicate that the transmission distance of SARS-CoV-2 might be 4 m.


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