April 14, 2020

Universal screening for SARS-CoV-2 in women admitted for delivery, and aerosol and surface distribution of SARS-CoV-2 in hospital wards

By Denise Baez

NEW YORK -- April 14, 2020 -- In today’s DG Alert, we cover universal screening for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in women admitted for delivery, and aerosol and surface distribution of SARS-CoV-2 in hospital wards.

According to a study published in The New England Journal of Medicine, there are benefits to universal testing for SARS-CoV-2 in pregnant women who are admitted to the hospital for delivery. 

Desmond Sutton, MD, Columbia University Irving Medical Center, New York, New York, and colleagues implemented universal testing with nasopharyngeal swabs and a quantitative polymerase-chain-reaction test to detect SARS-CoV-2 in women who were admitted to the New York-Presbyterian Allen Hospital and Columbia University Irving Medical Center for delivery between March 22, 2020, and April 4, 2020. 

Of the 215 women admitted for delivery, only 4 (1.9%) had fever or other symptoms on admission and all 4 tested positive for SARS-CoV-2. 

Nasopharyngeal swabs were obtained from 210 of the remaining 211 asymptomatic women and 29 (13.7%) were positive for SARS-CoV-2. Thus, 29 of the 33 patients who were positive for SARS-CoV-2 at admission (87.9%) had no symptoms of COVID-19 at presentation. Of the 29 women who had been asymptomatic but who were positive for SARS-CoV-2 on admission, fever developed in 3 (10%) before postpartum discharge (median length of stay, 2 days). 

One patient with a swab that was negative for SARS-CoV-2 on admission became symptomatic postpartum and repeat testing 3 days after the initial test was positive.

“Although this prevalence has limited generalizability to geographic regions with lower rates of infection, it underscores the risk of COVID-19 among asymptomatic obstetrical patients,” the authors wrote. “Moreover, the true prevalence of infection may be underreported because of false negative results of tests to detect SARS-CoV-2.”

The authors noted that universal testing may help hospitals determine isolation practices and bed assignments, inform neonatal care, and guide the use of personal protective equipment. 

In another study, published in Emerging Infectious Diseases, researchers collected air and surface samples from potentially contaminated objects at Huoshenshan Hospital, Wuhan, China, and found SARS-CoV-2 widely distributed on floors, computer mice, trash cans, and sickbed handrails. 

Importantly, air samples detected the virus in the air more than 4 metres away from patients, suggesting that the transmission distance of SARS-CoV-2 might be 4 metres, not 2. 

Zhen-Dong Guo, MD, Academy of Military Medical Sciences, Beijing, China, and colleagues collected swam samples from the intensive care unit (ICU) and the general ward (GW) between February 19 and March 2. The ICU housed 15 patients with severe COVID-19 and the GW housed 24 patients with milder disease. 

The rate of positivity was relatively high for floor swab samples (ICU, 70%; GW, 15.4%), perhaps because of gravity and air flow causing most virus droplets to float to the ground, the authors noted. 

“In addition, as medical staff walk around the ward, the virus can be tracked all over the floor, as indicated by the 100% rate of positivity from the floor in the pharmacy, where there were no patients,” the authors reported. “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. We highly recommend that persons disinfect shoe soles before walking out of wards containing patients with COVID-19.”

The rate of positivity was also relatively high for the surface of the objects that were frequently touched by medical staff or patients. The highest rates were for computer mice (ICU, 75%; GW, 20%), followed by trash cans (ICU, 60%; GW, 0%), sickbed handrails (ICU, 42.9%; GW, 0%), and doorknobs (GW, 8.3%). Sporadic positive results were obtained from sleeve cuffs and gloves of medical staff, suggesting that medical staff should perform hand hygiene practices immediately after patient contact.

The researchers then assessed the risk for aerosol transmission of SARS-CoV-2 by collecting air in the isolation ward of the ICU and GW 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. 

Rates of positivity differed by air sampling site. Sampling sites were located near the air outlets (site 1), in patients’ rooms (site 2), and around the doctor’s office area (site 3). 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,” the authors wrote. “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 metres.”

Because environmental contamination was greater in the ICU than in the GW, the authors recommend that stricter protective measures be taken by medical staff working in the ICU. 

SOURCE: The New England Journal of Medicine, Emerging Infectious Diseases
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