Like most of us, I've been struggling to balance my needs to be productive, panic, and perform self care....so when I came across this article today, the balance shifted just enough to drive me to my keyboard...
One of the more confusing issues related to the recent COVID-19 pandemic is the question of whether or not people should be wearing face masks. When cases began appearing outside of China, officials made it clear that face masks should not be worn by the general public. The driving force behind this was the need to reserve face masks for medical professionals. If the public were to hoard face masks in the same way they were hoarding toilet paper, protection for those directly treating patients would be severely compromised.
However, in the last week, this recommendation has gotten hazier. The quick answer is that face masks are not the best protective measure for healthy people when they need to go into public. Social distancing has been the most effective tool thus far for reducing the spread of the virus. Instead, face masks are a measure to prevent people carrying the virus from spreading it to healthy individuals, especially when they do not show symptoms.
SARS-CoV2 (the name of the virus that causes the disease COVID-19, like HIV is the virus causes the disease AIDS) differs from other related viruses in the potential lag time between infection and symptoms. This incubation period is the time between exposure to the virus and onset of symptoms. The influenza virus has an incubation period of about 2 days, and SARS had an incubation period of 2 to 7 days. SARS-CoV2 has a reported incubation period of anywhere between 5 and 14 days. During this time, an infected individual may not display any of the symptoms of COVID-19.
Initial measures to control the spread of the virus relied heavily on screening for fever, cough, and chest xrays to identify lower respiratory infections....all of these would exclude individuals in this extended incubation period. It has also been estimated that many infected people experience mild symptoms or are symptom free. This too would add to the frequency of infected people unknowingly spreading the virus.
Additionally, the time during the course of SARS-CoV2 infection when an infected person is most contagious, differs from these other related viruses. Influenza is most contagious in the one or two days before symptoms appear, and SARS was most contagious when individuals were displaying symptoms. While a lot of laboratory research and data from real clinical cases is ongoing, it is believed the SARS-CoV2 is most contagious before symptoms occur, and individuals could continue spreading the virus for 2 weeks after their symptoms resolve. This drastically increases the likelihood that an individual that appears healthy will not take precautions, because they have no idea that they are infected.
The CDC released a recommendation today for everyone to wear cloth face masks in public. As a scientist and skeptic, I was interested to see this Nature paper detailing a controlled study on the ability of face masks to control amount of virus released from respiratory droplets and aerosols (aka spit and snot).
Respiratory virus shedding in exhaled breath and efficacy of face masks
Leung et al. Nature Medicine.
Brief Communication Published: 03 April 2020
In this paper the researchers studied individuals that had been infected with influenza or one of the two viruses responsible for seasonal colds: rhinovirus or coronavirus (same family but different strain than SARS-CoV2). The researchers measured viral RNA in the nose, throat, and exhaled breath particles. The breath samples were collected with a face mask or without. Samples were collected over 30 minutes, including if the patient coughed during that time.
Masks used in this study were simple surgical masks, not the N95 masks that have been in short supply in hospitals. N95 are specifically made to filter out small particles. Surgical masks create a physical barrier and are able to filter out larger particles, especially in the immediate environment. The surgical mask is thought to be a sufficient control for SARS-CoV2 because it is not thought to be spread through the air, but through direct contact with respiratory droplets. These droplets are formed when you sneeze, cough, or even talk (when you say it and spray it).
Virus was detected in exhaled breath from 20-35% of individuals with all three viral infections. When face masks were worn, this dropped to 4% in influenza infected individuals. Even more striking is that individuals with coronavirus infections had no detectable virus in their breath when they wore a face mask. Conversely, the presence of a face mask did not affect the amount of rhinovirus detected in exhaled breath.
The authors acknowledge several limitations in their study, including the fact that virus was not detected in the breath of all infected individuals. They argue that their measurements were meant to more accurately replicate real life, and it may indicate that not all respiratory droplets exhaled by infected individuals will contain virus, but it may also just be a limit to their collection method. In spite of this, it is still clear that simple surgical face masks were able to significantly reduce the virus detected.
While this is not a direct test of SARS-CoV2, the data is presented on a related coronavirus. It strongly suggests that face mask usage will be equally beneficial in the prevention of SARS-CoV2 spread.
It is important to note that the CDC is recommending a simple cloth face mask when sufficient distancing is not possible (essential store visits). They stress the fact that N95 masks and surgical masks are still in short supply for medical professionals, and these less elaborate masks are appropriate for most people. There are plenty of online resources to sew your own mask, but we can also take a fashion tip from old west outlaws and use a bandanna or scarf.
Above all, masks are not a substitution for social distancing, which is proving to be the best way to flatten the curve and prevent our health care system from collapsing under the demands of COVID-19. While you don't feel sick right now, the insidious nature of this virus is that feeling sick doesn't necessarily mean you are not infected. When we work with human blood in the laboratory, we have to use "universal precautions", in which we treat all blood as though it is infectious. In these times, we need to use universal precautions and act as though everyone is infected, even yourself. In this way we can hope to prevent everyone from actually getting infected.
Sources cited:
Respiratory virus shedding in exhaled breath and efficacy of face masks
Leung et al. Nature Medicine.
Brief Communication Published: 03 April 2020
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover.html
https://www.cdc.gov/flu/about/disease/spread.htm
https://www.cdc.gov/sars/about/faq.html
https://www.uptodate.com/contents/coronavirus-disease-2019-covid-19
One of the more confusing issues related to the recent COVID-19 pandemic is the question of whether or not people should be wearing face masks. When cases began appearing outside of China, officials made it clear that face masks should not be worn by the general public. The driving force behind this was the need to reserve face masks for medical professionals. If the public were to hoard face masks in the same way they were hoarding toilet paper, protection for those directly treating patients would be severely compromised.
However, in the last week, this recommendation has gotten hazier. The quick answer is that face masks are not the best protective measure for healthy people when they need to go into public. Social distancing has been the most effective tool thus far for reducing the spread of the virus. Instead, face masks are a measure to prevent people carrying the virus from spreading it to healthy individuals, especially when they do not show symptoms.
SARS-CoV2 (the name of the virus that causes the disease COVID-19, like HIV is the virus causes the disease AIDS) differs from other related viruses in the potential lag time between infection and symptoms. This incubation period is the time between exposure to the virus and onset of symptoms. The influenza virus has an incubation period of about 2 days, and SARS had an incubation period of 2 to 7 days. SARS-CoV2 has a reported incubation period of anywhere between 5 and 14 days. During this time, an infected individual may not display any of the symptoms of COVID-19.
Initial measures to control the spread of the virus relied heavily on screening for fever, cough, and chest xrays to identify lower respiratory infections....all of these would exclude individuals in this extended incubation period. It has also been estimated that many infected people experience mild symptoms or are symptom free. This too would add to the frequency of infected people unknowingly spreading the virus.
Additionally, the time during the course of SARS-CoV2 infection when an infected person is most contagious, differs from these other related viruses. Influenza is most contagious in the one or two days before symptoms appear, and SARS was most contagious when individuals were displaying symptoms. While a lot of laboratory research and data from real clinical cases is ongoing, it is believed the SARS-CoV2 is most contagious before symptoms occur, and individuals could continue spreading the virus for 2 weeks after their symptoms resolve. This drastically increases the likelihood that an individual that appears healthy will not take precautions, because they have no idea that they are infected.
The CDC released a recommendation today for everyone to wear cloth face masks in public. As a scientist and skeptic, I was interested to see this Nature paper detailing a controlled study on the ability of face masks to control amount of virus released from respiratory droplets and aerosols (aka spit and snot).
Respiratory virus shedding in exhaled breath and efficacy of face masks
Leung et al. Nature Medicine.
Brief Communication Published: 03 April 2020
In this paper the researchers studied individuals that had been infected with influenza or one of the two viruses responsible for seasonal colds: rhinovirus or coronavirus (same family but different strain than SARS-CoV2). The researchers measured viral RNA in the nose, throat, and exhaled breath particles. The breath samples were collected with a face mask or without. Samples were collected over 30 minutes, including if the patient coughed during that time.
Masks used in this study were simple surgical masks, not the N95 masks that have been in short supply in hospitals. N95 are specifically made to filter out small particles. Surgical masks create a physical barrier and are able to filter out larger particles, especially in the immediate environment. The surgical mask is thought to be a sufficient control for SARS-CoV2 because it is not thought to be spread through the air, but through direct contact with respiratory droplets. These droplets are formed when you sneeze, cough, or even talk (when you say it and spray it).
Virus was detected in exhaled breath from 20-35% of individuals with all three viral infections. When face masks were worn, this dropped to 4% in influenza infected individuals. Even more striking is that individuals with coronavirus infections had no detectable virus in their breath when they wore a face mask. Conversely, the presence of a face mask did not affect the amount of rhinovirus detected in exhaled breath.
The authors acknowledge several limitations in their study, including the fact that virus was not detected in the breath of all infected individuals. They argue that their measurements were meant to more accurately replicate real life, and it may indicate that not all respiratory droplets exhaled by infected individuals will contain virus, but it may also just be a limit to their collection method. In spite of this, it is still clear that simple surgical face masks were able to significantly reduce the virus detected.
While this is not a direct test of SARS-CoV2, the data is presented on a related coronavirus. It strongly suggests that face mask usage will be equally beneficial in the prevention of SARS-CoV2 spread.
It is important to note that the CDC is recommending a simple cloth face mask when sufficient distancing is not possible (essential store visits). They stress the fact that N95 masks and surgical masks are still in short supply for medical professionals, and these less elaborate masks are appropriate for most people. There are plenty of online resources to sew your own mask, but we can also take a fashion tip from old west outlaws and use a bandanna or scarf.
Above all, masks are not a substitution for social distancing, which is proving to be the best way to flatten the curve and prevent our health care system from collapsing under the demands of COVID-19. While you don't feel sick right now, the insidious nature of this virus is that feeling sick doesn't necessarily mean you are not infected. When we work with human blood in the laboratory, we have to use "universal precautions", in which we treat all blood as though it is infectious. In these times, we need to use universal precautions and act as though everyone is infected, even yourself. In this way we can hope to prevent everyone from actually getting infected.
Sources cited:
Respiratory virus shedding in exhaled breath and efficacy of face masks
Leung et al. Nature Medicine.
Brief Communication Published: 03 April 2020
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover.html
https://www.cdc.gov/flu/about/disease/spread.htm
https://www.cdc.gov/sars/about/faq.html
https://www.uptodate.com/contents/coronavirus-disease-2019-covid-19
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