Infectious Disease Updates
August 1, 2025 7 minutes read
By Carol A. Kemper, MD, FIDSA
Do Gowns Help Prevent Transmission of Respiratory Viruses?
Source: Orsel LM, Severin JA, Knoester M, et al. The role of gowns in preventing nosocomial transmission of respiratory viruses: A systematic review. J Hosp Infect. 2025; Jun 16. doi: 10.1016/j.jhin.2025.05.023. [Online ahead of print].
The benefit of contact precautions using gowns and gloves in preventing transmission of viral respiratory infection to healthcare workers (HCWs) and other patients has not been conclusively demonstrated. Only one study from the 1990s compared the use of gowns vs. no gowns in a real-life patient setting and found no difference in HCW respiratory syncytial virus (RSV) infection. And yet, contact precautions are recommended for most viral respiratory infections. Gowns are expensive, they have a significant carbon footprint, we go through thousands of them per day, and they increase the work burden for HCWs. They also may adversely contribute to the patient experience. Shouldn’t we prove they are really necessary?
These authors examined available databases for research studies pertaining to the use of gowns in the transmission of respiratory viral agents, finding 30 publications. Twenty of these were research trials; more than half (53%) were conducted in Asia; only five (17%) were conducted in the United States.
The studies were grouped into four categories:
Viral contamination rate on HCWs after patient care
Twelve publications were examined, 11 of which focused on SARS-CoV-2 and one on other respiratory viruses. These studies included 18 experiments using five different types of clothing materials, with varying HCW-patient contact for anywhere from 15 to 350 minutes. Polymerase chain reaction testing was used in all of the studies; only one performed viral isolation. Half of the studies found 0% viral particle contamination on gowns. Four of five studies performing cycle thresholds found very low viral loads. Only one study found a high rate of contamination (77%), where nurses submitted a large number of torso samples, but generally rates of contamination were low, e.g., torso (19%), shoes (15%), sleeves (12%).
Viral contamination of different types of fabrics in the laboratory setting
Seven studies were examined, six of which focused on SARS-CoV-2 and one on influenza A. All of the studies assessed viable virus in various types of fabric or clothing when inoculated with virus. The studies used various detection methods, but most used cultures with plaque assay for measuring viable virus. Generally, viable virus persisted longer on fluid-resistant materials and for less time on absorbent materials. For example, viable virus persisted on Tyvek gowns for up to seven and 14 days, and six days on plastic gowns. In contrast, viable virus persisted for up to three days and four hours on cotton fabric and only 2.5 hours on polyester. In another study, the combination of cotton and polyester performed the best, with only a small amount of SARS-CoV-2 virus found after 10 minutes compared with other materials.
Not wearing PPE and HCW infection
Seven studies examined the use of personal protective equipment (PPE) in HCWs who reported illness compared with no illness. Four of these studies focused on SARS-CoV-2 and the other three focused on SARS-CoV-1. Six of these studies examined the use of gowns vs. aprons or coveralls vs. no gowns. Only one study found that not wearing PPE was associated with an increase in the frequency of HCW infection, but this was only statistically significant when HCWs were performing aerosolizing procedures. Most studies found no relationship between not wearing gowns — or breaches in using gowns — and HCW infection.
HCW illness when wearing different clothing materials in the patient care setting
Two studies simulated viral contamination by using ultraviolet (UV) fluorescent gel, finding that more UV substance was found on the bare arms of HCWs foregoing gowns but wearing short sleeves, although this was no longer the case when hand and arm hygiene was performed. Two studies focused on SARS-CoV-2 and RSV using plastic vs. cotton gowns. During a three-month period, no HCWs became ill with COVID when wearing a cotton gown. Further, over an eight-month period, there was no difference in the frequency of HCW illness when caring for patients with RSV with or without a gown.
These studies provide a mixed bag of information on rates of viral contamination of different types of gowns and materials. Most studies found no good evidence for gowning up reducing the risk of transmission of viral respiratory illness to HCWs or other patients, and the rates of viral contamination when present on various clothing/gown materials are probably too small to be of concern. Currently, we follow recommendations for gowning with most respiratory viruses, generating a huge amount of inconvenience and waste. It would be good to have a proper study demonstrating this is without basis. The authors speculated that bare arms (short sleeves) with good hygiene was a reasonable alternative to gowns.
How to Assess the ‘Wobble’ in Your IGRA?
Source: Wang M-S, Li-Hunnam J, Chen Y-L, et al. Conversion or reversion of interferon gamma release assays for Mycobacterium tuberculosis infection: A systematic review and meta-analysis. Clin Infect Dis. 2025;80(1):168-179.
An often-asked question for infectious disease specialists is the interpretation of interferon gamma release assays (IGRA) in the diagnosis of latent or active tuberculosis (TB), especially when used as a screening tool in low-risk populations or in those with immunosuppression. Discordant results or “wobble” often occur, especially around the cut-off value, which leads to confusion, anxiety, and additional workup. How to assess the “wobble”?
Consideration of the possible reasons behind conversion or reversion is helpful when interpreting serial test results. IGRA conversion may be due to a multitude of factors, including exposure to TB or TB antigens, changes in immune status, or assay variability. Conversion also may occur in patients with active TB who convert their IGRA during active treatment, either due to delayed conversion or immune reconstitution. Similarly, reversion of a positive test result to negative may be due to changes in immune system status, clearance of TB infection (either naturally or as the result of treatment), or assay variability. Keep in mind that the frequency of indeterminate results varies from 3% to 10%, depending on the population studied; and the frequency of false-negative test results may be as high as 10% to 20% in persons with active TB.
These authors screened public databases for relevant publications, arriving at 244 studies of IGRA transformation for systematic review. These studies encompassed more than 101,000 assay results (of which about 70% were either the QuantiFERON (QFT, Qiagen), QuantiFERON-TB Gold assay (QFT-G), QuantiFERON-TB Gold In-Tube assay (QFT-GIT), or QuantiFERON-TB Gold Plus (QTF-Plus), and about 30% were the T-SPOT.TB assay). Less than 10% of these repeated test results were obtained within one month; most were obtained six months or more later. Repeated testing generated information on the frequency of conversion (negative to positive) and reversion (positive to negative), depending on the duration of time between test results. Further testing revealed whether this change in the test result was considered “transient” (reverting back to the original result).
The estimated pooled frequency of IGRA conversion was 7.3% (range, 6.1% to 8.5%). Conversion was more frequent among patients with longer testing intervals, with only 2.3% converting if testing was repeated within one month vs. 8.2% if more than one month between tests. Conversion was common in persons being worked up for exposure to TB (12.5%), and these data indirectly suggest that waiting more than one month for screening for exposure provides more reliable results. The pooled rate of transient conversion (negative to positive to negative) was estimated at 46% (range, 36% to 56.4%). This frequency of transient conversions increased with an increasing interval between the first and second tests.
IGRA test reversion (positive to negative) was more common than conversion, with an estimated pooled frequency of test reversion of 22.8% (20.1% to 25.7%). Transient reversion events occurred in 19.6% (meaning positive to negative to positive). In contrast to the pattern of transient conversions over time, there was a decrease in transient reversion events with a longer interval between tests, and for intervals longer than six months between the first and second tests the pooled rate of transient reversion was 0%. In other words, about 81% of people who reverted their tests remained negative on repeated testing, especially if there was a longer interval between test results.
Changes in indeterminate test results were more frequent with longer intervals between testing: 41% of those with an indeterminate test result with repeat testing within one month remained indeterminate. In contrast, if you waited more than one month and less than six months or greater than six months, only 23.4% and 12% of those indeterminates remained indeterminate, respectively. Most people with indeterminate results changed to negative, and only rarely (1.2%) changed to positive. Changes from indeterminate to negative were increasingly common with longer intervals between testing (72.6% negative at more than six months).
Test conversion was associated with older age, the study area (countries endemic for TB), and treatment for both latent and active TB. Persons with active TB had a 22.7% risk of test conversion on follow-up. Women were less likely than men to have transient conversions or reversions. Bacille Calmette-Guérin (BCG) vaccination/tuberculin skin testing (TST) was strongly associated with a reduced risk of IGRA reversion (TST 6.7% vs. no TST 33.2%), and treatment for either latent or active TB was associated with a reduced risk of IGRA reversion.
The authors commented that the agreement between the TST, QFT, and T-SPOT.TB in identifying conversion or reversion events was poor. Therefore, it is not helpful to attempt to clarify test results by using an alternate method.
Carol A. Kemper, MD, FIDSA, is Medical Director, Infection Prevention, El Camino Hospital, Palo Alto Medical Foundation.
Do Gowns Help Prevent Transmission of Respiratory Viruses? How to Assess the ‘Wobble’ in Your IGRA?
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