Data do not back cloth masks to limit COVID-19, experts say
Filed Under:
COVID-19
Mary Van Beusekom | News Writer | CIDRAP News
| Apr 09, 2020
Limited, indirect evidence from lab studies suggests that homemade fabric masks may capture large respiratory droplets, but there is no evidence they impede the transmission of aerosols implicated in the spread of COVID-19, according to a paper published yesterday by the National Academy of Sciences, Engineering, and Medicine.
In the paper, the National Academies’ Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats said that, because no studies have been done on the effectiveness of cloth masks in preventing transmission of coronavirus to others, it is impossible to assess their benefits, if any.
The paper was prepared by committee members Richard Besser, MD, of the Robert Wood Johnson Foundation, and Baruch Fischhoff, PhD, of Carnegie Mellon University, and two subject matter experts contributed. It was approved by Committee Chair Harvey Fineberg, MD, PhD, and was peer-reviewed by seven additional US experts.
In the absence of widespread availability of more effective protection and to preserve surgical masks and respirators for healthcare workers, homemade fabric masks have been proposed to limit spread of coronavirus by wearers who might be contagious but are asymptomatic or pre-symptomatic. The US Centers for Disease Control and Prevention recently endorsed their use.
Many factors at play in gauging effectiveness
Committee members point out that research suggests that COVID-19 can spread via invisible droplets as small as 5 microns and by tiny bioaerosol particles as well as via visible respiratory droplets just by breathing.
Infected yet asymptomatic people are of particular concern because the particles they breathe are predominantly bioaerosols. “To complicate matters further, different individuals vary in the extent to which they emit bioaerosols while breathing,” they said.
Because different masks have different filtering capacities and the role of droplet size on disease transmission is unknown, it is difficult to predict the effectiveness of these masks, the authors said. “The extent of any protection will depend on how the masks are made and used,” they wrote. “It will also depend on how mask use affects users’ other precautionary behaviors, including their use of better masks, when those become widely available.”
Those behaviors may reduce or enhance homemade fabric masks’ overall effects on public health, they noted. “The current level of benefit, if any, is not possible to assess,” they said.
Michael Osterholm, PhD, MPH, director of the Center for Infectious Disease Research and Policy (CIDRAP), who contributed to the paper along with Sundaresan Jayaraman, PhD, of the Georgia Institute of Technology in Atlanta, said in his weekly CIDRAP podcast yesterday that, because aerosols likely play an important role in coronavirus transmission, cloth masks will do little, if anything, to limit spread of the disease.
Even more, he worries that encouraging cloth masks is emboldening people to try to get surgical masks for better protection, taking them away from frontline healthcare workers, who desperately need them. “If we’re right now in a major shortage status—and we will be for the kind of N95 and surgical mask protection—the public should not ever try to get these,” he said.
CIDRAP publishes CIDRAP News.
Research needed on effectiveness, precautions
In the report, the committee members called for research to yield clear instructions on how to properly make, fit, use, and clean homemade fabric masks.
Studies also need to explore estimates of the protection that such masks afford users and others in different settings (eg, in places in which the likelihood of contact is higher, like grocery stores, compared with wearing masks everywhere), they wrote. In addition, they said data need to be gathered on effective reinforcement of other precautions, such as physical (social) distancing.
“That research could provide policy makers with estimates of the net effect of encouraging use of homemade cloth masks on public health, with realistic estimates of how such masks will be made and used, as well as how they will affect other precautionary behaviors of users and others who observe and interact with them,” they said.
Effectiveness of convalescent plasma therapy in severe COVID-19 patients
Today, 03:42 PM
Significance
COVID-19 is currently a big threat to global health. However, no specific antiviral agents are available for its treatment. In this work, we explore the feasibility of convalescent plasma (CP) transfusion to rescue severe patients.
The results from 10 severe adult cases showed that one dose (200 mL) of CP was well tolerated and could significantly increase or maintain the neutralizing antibodies at a high level, leading to disappearance of viremia in 7 d. Meanwhile, clinical symptoms and paraclinical criteria rapidly improved within 3 d. Radiological examination showed varying degrees of absorption of lung lesions within 7 d.
These results indicate that CP can serve as a promising rescue option for severe COVID-19, while the randomized trial is warranted.
Abstract
Currently, there are no approved specific antiviral agents for novel coronavirus disease 2019 (COVID-19). In this study, 10 severe patients confirmed by real-time viral RNA test were enrolled prospectively. One dose of 200 mL of convalescent plasma (CP) derived from recently recovered donors with the neutralizing antibody titers above 1:640 was transfused to the patients as an addition to maximal supportive care and antiviral agents. The primary endpoint was the safety of CP transfusion. The second endpoints were the improvement of clinical symptoms and laboratory parameters within 3 d after CP transfusion. The median time from onset of illness to CP transfusion was 16.5 d. After CP transfusion, the level of neutralizing antibody increased rapidly up to 1:640 in five cases, while that of the other four cases maintained at a high level (1:640). The clinical symptoms were significantly improved along with increase of oxyhemoglobin saturation within 3 d. Several parameters tended to improve as compared to pretransfusion, including increased lymphocyte counts (0.65 × 109/L vs. 0.76 × 109/L) and decreased C-reactive protein (55.98 mg/L vs. 18.13 mg/L). Radiological examinations showed varying degrees of absorption of lung lesions within 7 d. The viral load was undetectable after transfusion in seven patients who had previous viremia. No severe adverse effects were observed.
This study showed CP therapy was well tolerated and could potentially improve the clinical outcomes through neutralizing viremia in severe COVID-19 cases. The optimal dose and time point, as well as the clinical benefit of CP therapy, needs further investigation in larger well-controlled trials.
https://www.pnas.org/content/early/2020/04/02/2004168117
At least some of the trick to masks is static charge of the fabric grabbing the virus to cause a roadblock as other virus latch onto each other in clumps too big to get thru the mesh of a material. Like dirt on a window-screen. Three layers should create a static charge n each layer just by rubbing against each other, and why wouldn’t it be good enough for a quick grocery store trip as long as you didn’t have to stand in long lines? Maybe not so much a single layer silk scarf.
limited, indirect evidence isn’t enough evidence to discourage people from wearing something that helps block two of three critical facial areas.