Research Updates on COVID-19: Masks & More

Weekly COVID-19 Research Update
April 8, 2020

During the COVID-19 pandemic, it is vital to make objective and informed decisions that affect your family and loved ones. As part of Princeton Longevity Center’s strategic partnership with PinnacleCare, we are excited to bring you their Pandemic Response Research updates as a complimentary resource through the remainder of this crisis. These updates will bring you factual, objective, scientific information to help make safe decisions for you, your family and your community. Updates, while scientifically based, are easy to understand and will include both resources and references for a more clinical insight.

CDC Recommendation Updates

Between April 2 and April 6, the CDC published updates on over 20 of the pages on its COVID-19 website. One notable update was to the information on the transmission of SARS-CoV-2 (CDC, How COVID-19 Spreads, 2020). Added to the page is guidance pertaining to the growing amount of evidence that transmission by asymptomatic individuals is possible. The page was also updated to include that there is widespread community transmission in the United States of SARS-CoV-2 and that SARS-CoV-2 is transmitting more readily than influenza.

There were also major updates on the page related to use of personal protective equipment (PPE). Previously, the page simply included guidance for the use of each type of product. The new update acknowledges the severe nationwide shortages and recommends that “all U.S. healthcare facilities should begin using PPE contingency strategies now.”

Based on the updated information on transmission of the virus and the limited number of medical grade masks available, the CDC also changed its recommendation for the use of masks by the general public (CDC, Recommendation Regarding the Use of Cloth Face Coverings, 2020). The CDC recommendation now states,

“The CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies) especially in areas of significant community-based transmission.”

They also stress that continuing to practice social distancing is the best way to slow transmission of SARS-CoV-2. Additionally, they mention that

“The cloth face coverings recommended are not surgical masks or N-95 respirators. Those are critical supplies that must continue to be reserved for healthcare workers and other medical first responders, as recommended by current CDC guidance.”

Efficacy of Cloth Face Coverings to Slow the Transmission of COVID-19

There has been much discussion about who should wear masks during the current COVID-19 outbreak.

It is simply not known if the general use of masks will help to prevent transmission of SARS-CoV-2 in the community. 

There are a few clinical trials that investigate the possible utility of wearing non-medical masks during an outbreak of respiratory illness. Most available information comes from trials describing mask use by healthcare workers in clinical settings. There are a few that look at the effect of using medical-grade masks on transmission of respiratory illness in a household setting, and some that investigate the differences in efficacy of medical-grade masks and homemade cloth masks. However, none of the trials investigate situations similar to the current question facing the world today: Does use of non-medical masks prevent or slow transmission of COVID-19?

Masks can be used to prevent contamination of surfaces with a droplet-spread communicable disease by reducing aerosol transmission from coughing, sneezing, or other methods (Davies, 2013). They may also stop viral spread by preventing body fluids from reaching the mouth and nose and by preventing individuals from touching their mouth and nose. Studies of respiratory infection transmission in college dorms and in cases of parents caring for a sick child show that use of a medical-grade mask does reduce the risk of influenza-like illnesses (reduction of between 35% and 51% in Aiello, 2020 and between 60% and 80% in MacIntyre, 2009).

A collaboration between researchers at several institutions from Hong Kong, the United States, and the WHO was just released investigating the amount of multiple types of viruses expelled during exhalation with and without a mask (Leung et al., 2020). Use of masks to prevent transmission of viral infection from sick individuals is called source control. The viruses investigated were coronaviruses, influenza viruses, and rhinoviruses. The strain of coronavirus was the mild, seasonal form and not the SARS-CoV-2 strain of the virus. In the study, 246 participants provided breath samples collected over 30 minutes either with or without a medical-grade surgical face mask.

The two types of infectious material examined were respiratory droplets, which are larger and fall out of the air near the source, and fine-particle aerosols, which are smaller and stay aloft in the air for longer.

Out of the total group, the researchers were able to isolate and identify the cause of the participant’s upper respiratory infection in 123 participants, and 90% of the infections were human (seasonal) coronavirus, influenza virus, or rhinovirus, with rhinovirus representing the most infections. Viral shedding was measured in nasal swabs and throat swabs, which was compared to the amount of virus in respiratory droplet samples and aerosol samples with or without a medical-grade surgical mask. Viral shedding was the highest in nasal swabs for all three viruses. The researchers then determined the number of participants who had viral RNA detected in respiratory droplets or aerosols.

The values in the table marked in red were found to have a statistically significant difference in the amount of virus detected with use of a mask. The difference in the amount of virus detected was found to be statistically the same with the rest of the values.

Based on this information, the researchers concluded that seasonal coronaviruses can be transmitted in aerosols produced during normal breathing. However, even without a face mask, there were low amounts of viral shedding from people with influenza virus and seasonal coronavirus in both aerosols and respiratory droplets. This observation suggests that prolonged close contact would be required for transmission to occur, even if transmission was primarily via aerosols. The difference in the amount of virus detected with and without a surgical mask showed that masks reduced detection of influenza virus RNA in respiratory droplets and coronavirus RNA in aerosols.

The researchers stated that medical-grade, surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals.

There are a limited number of clinical trials investigating the efficacy of cloth masks compared to medical-grade surgical or procedural masks. Comparison of the effect of cloth masks and medical-grade masks in healthcare workers indicates that cloth masks increase the risk of infection from influenza-like-illnesses. The increase is thought to stem from a 97% rate of particle penetration with cloth masks as well as increased moisture retention observed and the frequency and effectiveness of cleaning between uses (MacIntyre et al., 2015). A negative effect from moisture retention was also observed during the previous SARS outbreak in 2003 when the use of two medical-grade masks (double-masking) increased the risk of infection from moisture, liquid diffusion, and pathogen retention.

Testing of the physical attributes of different materials that could be used to make masks during a pandemic-induced equipment shortage showed that there was some protection afforded from homemade masks (Davies et al., 2013). There was a decrease in the amount of microorganisms expelled while coughing with use of a mask made from t-shirt material, but the medical-grade surgical mask blocked three times as many microorganisms. Other materials tested were tea towels, vacuum bags, and pillowcases. The tea towels and vacuum bags were too hard to breathe through, and the researchers chose t-shirt material for further testing over the pillowcase due to a better fit on the face with a material that stretches. Overall the authors conclude that use of homemade masks “should only be considered as a last resort to prevent droplet transmission from infected individuals, but it would be better than no protection.”

The current situation does not allow for the general use of medical-grade masks due to severe supply shortages. Protective equipment must be reserved for healthcare workers and others who encounter sick individuals and are exposed to large amounts of the virus. 

There are two main points of view with regards to the use of non-medical masks for the general public.

  • There are a number of asymptomatic carriers of SARS-CoV-2 that can transmit infection through droplet formation and possibly aerosols. Widespread use of masks would prevent those who do not know they have COVID-19 from spreading it to others by reducing the contamination of surfaces with respiratory fluids.
  • Most people do not know how to correctly use a mask, and incorrect use of masks could lead to an increase in the spread of SARS-CoV-2. Transmission of the virus could occur from contamination of masks by moisture retention, improper techniques for donning a mask, poor fit of the mask, infrequent or inadequate cleaning of dirty masks, poor compliance, and a false sense of security leading to engagement in risky behaviors.

As mentioned above, there is currently no way to know which view more aptly describes the situation. However, many of the objections to the universal use of masks are due to concerns over improper use. If users are vigilant about proper use and care of masks without neglecting social distancing measures, the view that a homemade mask is better than nothing and may slow the spread from asymptomatic carriers may prevail.

Handling of Disposable and Reusable Masks

The World Health Organization recommends the following steps for proper use of a disposable mask during a respiratory virus outbreak.

  • Before putting on a mask, clean hands with alcohol-based hand sanitizer or soap and water.
  • Cover mouth and nose with mask, and make sure there are no gaps between your face and the mask.
  • Avoid touching the mask while using it; if you do, clean your hands with alcohol-based hand sanitizer or soap and water.
  • Replace the mask with a new one as soon as it is damp, and do not re-use single-use masks.
  • Do not touch the front of mask to remove it. Use the straps that are away from your face to remove the mask.
  • Discard used masks immediately in a closed bin, and clean hands with alcohol-based hand rub or soap and water.

In the case of a reusable mask, the last step would be replaced with instruction to secure used masks in an airtight container until they can be thoroughly washed with hot water and soap. There are also reported benefits of drying the cloths in the sun for additional antimicrobial effects. However, there is no study evidence on how frequently and what type of cleaning improves the efficacy of cloth masks (MacIntyre et al., 2015).

Other Measures for Reducing the Risk of SARS-CoV-2 Infection

Clinical research continues to indicate that the most effective way to prevent the transmission of SARS-CoV-2 is to diligently practice the social distancing guidelines suggested by the CDC and WHO. Detailed information on social distancing practices can be accessed at

Researchers have investigated the stability of SARS-CoV-2 in the air and on different types of surfaces (vanDoremalen et al., 2020). In general, SARS-CoV-2 had similar stability to SARS-CoV-1, the virus responsible for the SARS outbreak in 2003. This result suggests that differences in the transmission of these viruses probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with SARS-CoV-2 to shed and transmit the virus while asymptomatic, instead of increased presence of the virus in the environment. The researchers reported the amount of time that infectious virus could be recovered from different types of surfaces. The time period that they were able to obtain infectious virus from the surface was reported, and the researchers also mentioned that while some infectious virus was present at the end of the time period, the amount of infectious virus present was greatly reduced. They also reported the half-life of infectious virus, which is defined as the amount of time half of the virus on a surface degrades and is no longer able to cause an infection.

Time period and half-life for viable recovery of SARS-CoV-2:

  • Aerosols- infectious 3 hours or longer, half-life 1.1 to 1.2 hours
  • Plastic- infectious 72 hours, half-life 6.8 hours
  • Stainless steel- infectious 72 hours, half-life 5.6 hours
  • Copper- infectious 4 hours, half-life approximately 1 hour
  • Cardboard– infectious 24 hours, half-life approximately 3.5 hours

Based on this information, it is possible that SARS-CoV-2 can be transmitted from surfaces. The CDC recommends frequent handwashing and refraining from touching your face in order to reduce the risk of transmission in this manner. Frequent cleaning of high-touch areas such as hand rails and elevator buttons is also suggested.

In households that do not have sick individuals, the CDC recommends routine cleaning of frequently touched surfaces (for example: tables, doorknobs, light switches, handles, desks, toilets, faucets, sinks, and electronics) with household cleaners and EPA-registered disinfectants. If there is a member of the household with COVID-19 symptoms, more stringent cleaning is suggested. For example, the CDC recommends cleaning and disinfecting high-touch surfaces daily in household common areas (e.g. tables, hard-backed chairs, doorknobs, light switches, phones, tablets, touch screens, remote controls, keyboards, handles, desks, toilets, sinks) and isolating sick people in a specific room. More detailed information can be found at

There is currently no evidence of spread of the virus through food sources, including restaurant takeout, refrigerated, and packaged food. Specifically, the CDC states

“It may be possible that a person can get COVID-19 by touching a surface or object, like a packaging container, that has the virus on it and then touching their own mouth, nose, or possibly their eyes, but this is not thought to be the main way the virus spreads. In general, because of poor survivability of these coronaviruses on surfaces, there is likely very low risk of spread from food products or packaging.”

There are not currently recommendations for extra washing of food, packaging, or vegetables than would normally be needed. The WHO also reports that. “The likelihood of an infected person contaminating commercial goods is low and the risk of catching the virus that causes COVID-19 from a package that has been moved, travelled, and exposed to different conditions and temperature is also low.”


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