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Evidence

Overview

In an ongoing pandemic, you should, as much as your job, family, cohort and living situation allow, practice social distancing, wear a mask, routinely wash your hands to protect yourself from exposure, and self-monitor for symptoms.

Social Distancing – social distancing is a conscious effort to maintain distance between yourself and other people as a way to mitigate the spread of disease. Social distancing means staying at least 3-6 feet (1-2 meters) from other people as much as possible. Take precautions if you cannot maintain that distance, wear a mask with the highest protection level that you can, and wash your hands and/or use alcohol-based hand sanitizer after being in contact with someone else.

Wear A Mask – wearing a mask is important to decrease the transmission of COVID-19 through droplets from someone who coughs or sneezes, and from aerosolized virus. You should wear a mask when you are going to be within 3-6 feet (1-2 meters) of someone else, and if you will be in any indoor or outdoor space that is crowded or poorly ventilated. Masks vary in their ability to protect you and are ranked in order of evidence-based effectiveness as follows:

  • Fitted N95 - highest level of protection.
  • N95
  • Surgical Mask
  • 3-Layer Cloth Mask
  • Single Layer Cloth Mask
  • Bandana or Neck Gaiter - virtually no protection.

If you touch something that might be contaminated, including your mask, avoid touching your face, eyes, nose or mouth and wash your hands.

Wash Your Hands – hand washing is useful to decrease the transmission of COVID-19 through droplets from someone who coughs or sneezes. Wash your hands thoroughly for a full 20 seconds with soap and water. Plain soap kills COVID-19. There is no need to use anti-bacterial soap or caustic cleaners. Alcohol-based hand sanitizer can be used when soap and water are not readily available. Droplets can end up on you or surfaces. COVID-19 lasts different times on different materials and surfaces. Evidence-based estimated viral survival times are as follows:

  • Cooper – 4 hours
  • Aluminum – 2 to 8 hours
  • Paper + Cardboard – 24 hours
  • Stainless Steel + Plastics – 2 to 3 days
  • Glass + Ceramics – Up to 5 days
  • Food – COVID-19 does not seem to spread via food, but fruits and vegetables should be washed under running water before eating.
  • Water – COVID-19 is not found in bottled or tap water.

Self-Monitor – you should monitor yourself for symptoms of COVID-19 by checking yourself for symptoms on a routine basis. Remain alert for fever, loss of sense of taste or smell, cough or difficulty breathing. If you develop any of these or other symptoms consistent with COVID-19, you should stop work, school and any other socialized activity immediately, self-quarantine for 14 days and get tested.

If you have a health risks, health problems or co-morbidities you should shelter-at-home to minimize your risk of infection. If your health risks are significant you should find others to help you with required tasks such as grocery shopping and other needs.

Shelter-at-Home – shelter-at-home means you should work or attend school from home, if you can, and go out primarily for exercise and for essential tasks such as grocery shopping.

Self-Quarantine – self-quarantine means to stay at home and limit interactions with others. The intent is to separate people who are exposed or have high health risks, but do not have symptoms to see if they become symptomatic. A person can be contagious before symptoms begin, so this is critical to prevent the spread of COVID-19.

Get Tested – if you have symptoms consistent with COVID-19 confirm where you can get tested by checking online for testing sites near your address or zip code, by contacting your local health department, or telephone your health care provider or local medical center. Self-quarantine until you have received your results.

If your COVID-19 test results are negative, continue social distancing, wear a mask and routinely wash your hands to protect yourself from exposure, and continue to self-monitor for symptoms. If symptoms worsen and are consistent with COVID-19 telephone your health care provider and discuss if you should be retested.

If your test results are positive, self-isolate and telephone your health care provider to let them know so that your health can be monitored. All your recent contacts going back 72 to 96 hours should self-monitor their symptoms and self-quarantine. If they develop symptoms, they need to get tested.

Self-Isolate – self-isolate means do not leave home or get admitted to an isolation facility. If you self-isolate at home, avoid others in your residence. Make sure that you wear a mask and that all others in your residence wear a mask in your presence or in any rooms in which you spend time. Disinfect surfaces regularly. Monitor and recheck for symptoms that may require medical attention such as shortness of breath at rest, chest pain, persistently high fever despite fever lowering medicine, confusion, lightheadedness, or inability to eat or drink. Duration - 14 days from symptom onset, and 72 hours after fever disappears and improvement in respiratory symptoms. Any other members of your household will need to self-quarantine for 14 days after the resolution of your symptoms and get tested if they develop symptoms.

The Evidence

COVID-19 is a Coronaviridae virus, similar to SARS, MERS and related Coronaviridae that cause the common cold. COVID-19 is a respiratory contagion and its principal means of infection is through airborne transmission of virus. This has been evident since reports of early transmission within restaurants in Wuhan, China, and is now supported by a broad consensus.

The origin of the infection was in Wuhan, a transportation hub in China. Spread of the disease and onset of infections was directly related to travel patterns from Wuhan to Europe, the United States and other countries. Subsequent spread from Europe to the U.S., U.S. to Asia and all permutations have occurred. The elderly, the socioeconomically disadvantaged and essential workforces saw the first elevated case counts, but the virus has spread into both younger and more economically advantaged populations. The largest increase in cases in hard hit states in the U.S. is now in the 18-49 year-old age group, and this includes hospitalizations. Some of this represents increasing infection in the essential workforce in that age group, but there is an increasing percentage from the general community through exposure and infection from non-essential social gatherings, specifically bars, clubs and private parties.

COVID-19 spreads via from the expression of the virus from the lungs and airways of infected individuals into the air or onto surfaces through cough, sneeze, conversation or exhalation. Transmission occurs when an adequate number of virus find their way into the respiratory tract of another susceptible individual and are able to initiate infection. The route of viral attack is through the mouth, the nares (nostrils) of the nose or the tear ducts.

Direct airborne spread from individual-to-individual is the primary mode of infection, but there is a potential risk of spread from surfaces and materials upon which virus land, from transport on air pollutants and in wastewater. The risk of surface transmission in COVID-19, however, appears to low and is handled with routine hygiene with soap and water. Evidence-based estimated COVID-19 viral survival times on different materials and surfaces are as follows:

  • Cooper – 4 hours
  • Aluminum – 2 to 8 hours
  • Paper + Cardboard – 24 hours
  • Stainless Steel + Plastics – 2 to 3 days
  • Glass + Ceramics – Up to 5 days
  • Food – COVID-19 does not seem to spread via food, but fruits and vegetables should be washed under running water before eating.
  • Water – COVID-19 is not found in bottled or tap water.

There is currently no evidence for infection occurring through the skin, mucous membranes or the gastrointestinal tract.

Infection is dependent on four key factors:

  • First, the virus has to persist in the air or on surfaces in concentrations high enough to cause infection.
  • Second, enough virus needs to get into the respiratory tract of a susceptible individual.
  • Third, the health or health risk factors of that individual need to provide a potential attack target for the virus.
  • Fourth, the virus has to overcome the immune response of that individual.

Simply put, infection requires an adequate load of virus to end up in the respiratory tract of a susceptible host with the ability to overcome the protective immune response of that host so that the viruses can establish themselves and replicate. Like the majority of infectious diseases, exposure of the host to the contagion does not mean the virus will be successful in causing infection.

COVID-19 is more infective than some of the more virulent strains of influenza such as H1N1, but less infective than other SARS viruses such as SARS CoV and MERS and less infective than other zoonotic vectors such as Ebola or Marburg.

COVID-19 has morbidity and mortality across all age groups with a signature age- and health-risk related virulence. Its highest risk is in the elderly, increasing geometrically in virulence, morbidity and mortality from age 60 onward. It is more virulent across all age groups for individuals with co-morbidities, in particular those with respiratory, cardiac, immunologic and metabolic conditions, and in those with elevated body mass index (BMI).

In children it is a high risk to infants under one year-of-age, then relatively sparing of children into their early teens, returning to adult-similar virulence from early teens to adulthood. In children there is a codependent condition, called Multisystem Inflammatory Syndrome (MIS-C) which is similar in many characteristics to Kawasaki’s Disease and other inflammatory conditions in children. Like Kawasaki’s, MIS-C is rare and effectively treatable. It is a late post-infection syndrome, occurring primarily after a resolved acute symptomatic or asymptomatic COVID-19 infection. The prevention of MIS-C is to prevent COVID-19 infection in children in the first place – this is critical to understand.

In teenagers and adults under the age of 60, particularly those with minimal to no co-morbidities, infection appears to take a predominantly benign course, with minimal symptoms. There are three critical exceptions to this:

  • First, co-morbidities increase morbidity and mortality at all ages.
  • Second, the extent of exposure and viral load, as with all infectious diseases, can affect outcomes – the higher and more extensive the exposure, the greater the risk of infection and potential for more severe disease and death.
  • Third, certain individuals, with characteristics we do not yet understand become critically ill, even though they are otherwise healthy with no obvious co-morbidities or risk factors. This is sobering and worth repeating – otherwise healthy teenage to adult individuals can get severely ill, extremely rapidly and die. We do not clearly understand why, although research, genetic testing and clinical studies are underway to determine potential etiologies and risk factors. Of note is that we have seen this in other respiratory infectious diseases, particularly in the 1918 and 2009 H1N1 influenza pandemics where we saw significant numbers of healthy young adults and pregnant women rapidly decompensate and die. 80% of the 12,500 U.S. deaths from the 2009 H1N1 pandemic were under the age of 65.

If you touch something that might be contaminated, including your mask, avoid touching your face, eyes, nose or mouth and wash your hands.

In pregnancy COVID-19 does not appear to be teratogenic (cause birth defects), but since pregnancy co-morbidities include preeclampsia/hypertension, diabetes and functional respiratory and diaphragmatic compromise, current evidence indicates exposure and infection in pregnancy should be avoided and that severe illness in the mother presents significant maternal and fetal risk.

Prevention

Prevention of COVID-19 infection is straightforward. It requires preventing the transmission of a sufficient viral load of COVID-19 virus through the mouth, nose or tear ducts into the respiratory tract. If there is exposure, baseline health and early effective T-cell immune response are key factors in whether actual infection occurs. To reiterate, exposure does not mean infection. Viral load, health risk, susceptibility and immune response are all critical mediators.

Protection of the mouth and nares is best accomplished by a fitted, sealed and virally impermeable mask. A U.S. National Institute of Occupational Safety and Health (NIOSH) approved N95 is the current recommendation. Protection of the tear ducts is accomplished with glasses, googles or a face shield providing adequate eye coverage. As above, there is no reported transmission through the skin, mucous membranes or gastrointestinal tract, so the primary surface risk is from touching a contaminated surface and transmitting an adequate viral load to the tear ducts, nares or mouth. Avoidance of touching the face, eyes, nose or mouth offers primary protection, backed up with hand washing with soap and water or the use of 60% or greater alcohol-based hand sanitizer to neutralize the virus on hands and skin if soap and water are not readily available. Plain soap kills COVID-19. There is no need to use anti-bacterial soap or caustic cleaners.

Airborne viral load and risk are increased in confined or inadequately ventilated interior spaces. Like influenza, Legionnaire’s and other respiratory contagions, air conditioning and ventilation systems can increase spread if air is moved from an area of high viral load to others. This can be room-to-room or across a room along the path of airflow.

Ultraviolet light, including from sunlight, inactivates the virus and outdoor ventilation from wind and greater air exchange decreases COVID-19 transmission risk in outdoor spaces. Use of UV light in ventilation systems (HVAC) might decrease COVID-19 airborne risk, and human-safe UV light is under investigation.

Wearing a mask is important to decrease the transmission of COVID-19 through droplets from someone who coughs or sneezes, and from aerosolized virus. You should wear a mask when you are going to be within 3-6 feet (1-2 meters) of someone else, and if you will be in any indoor or outdoor space that is crowded or poorly ventilated. The evidence shows that a fitted N95 mask is effective in preventing significant virus from getting into our respiratory track. The key points are N95 and fitted. A properly sized, fitted and correctly worn mask is required. Cloth and surgical masks are less effective protection, have significantly less utility in preventing the spread of infection and require high compliance. Bandanas and neck gaiters have limited effectiveness.

The evidence-based effectiveness of different masks is as follows:

  • Fitted N95 - highest level of protection.
  • N95
  • Surgical Mask
  • 3-Layer Cloth Mask
  • Single Layer Cloth Mask
  • Bandana or Neck Gaiter - virtually no protection.

If you touch something that might be contaminated, including your mask, avoid touching your face, eyes, nose or mouth and wash your hands.

If you work in a setting with inadequate ventilation and/or where you risk exposure of under one meter for greater than 10-15 minutes to anyone else, you should use a fitted N95 mask and adequate eye protection – glasses, goggles or face shield. This includes but is not limited to health care, restaurant and commercial kitchens, elder and home care, at-risk teachers, grocery and retail clerks, close work construction, manufacturing, warehousing and transportation drivers.

If you are either indoors or outdoors and will be within one meter with anyone else not in your social distancing cohort for greater than 10-15 minutes, you should wear a protective close-fitting mask.

If you are outdoors, in your car, or out walking, running or biking alone or only with members of your social distancing cohort, and you are not at risk of being within one meter of anyone else not in your social distancing cohort for greater than 10-15 minutes, there is limited benefit to wearing a mask.

Glasses, googles and face shields, as well as glass or plexiglass barriers, provide protection of the eyes and transmission of the virus through the tear ducts.

Hand washing is important, primarily because we touch our eyes, nose and mouth with our hands, and if we have touched a surface containing adequate viral loads, virus can end up in our respiratory tract. The COVID-19 virus appears to have only moderate persistence on surfaces and does not have inherent mobility. COVID-19 virus does not crawl across surfaces, congregate socially or actively seek targets to infect. They are passive, fomite and airborne, and opportunistic when they end up in the respiratory tract of a susceptible host.

COVID-19 is similar to other respiratory contagions in that it is transmissible from infected individuals to others prior to the infected individual showing symptoms. This is often referred to as asymptomatic transmission, with leads to significant misunderstanding and misinterpretation of the evidence. Asymptomatic transmission implies that an individual who never develops symptoms is infectious to other people.

This is singularly the most feared and misrepresented aspect of COVID-19. True asymptomatic transmission might occur, particularly to high risk susceptible targets, but the evidence on super spreaders, where 10-20% of infected people are thought to cause of up 80% of subsequent infections, is that they are pre-symptomatic or mildly symptomatic when they infect others, not sub-clinical or asymptomatic. In addition, super spreader events are highly contingent on the type of venue, ventilation and contact proximity. To quote Christie Aschwanden on super spreaders in Scientific American, “Scientists have identified factors that catalyze such events, including large crowd sizes, close contact between people and confined spaces with poor ventilation. Current evidence suggests that it is mostly circumstances such as these, rather than the biology of specific individuals, that sets the stage for extreme spreading of the novel coronavirus.”

In addition, following basic respiratory disease principles, COVID-19 infectivity manifests prior to frank symptomatology. In the case of COVID-19 this means that a person is infective by shedding virus between 24 to 96 hours prior to the onset of symptoms.

Two key unknowns can be clarified by further research. Are people who are infected but do not show significant symptoms infective? Are people who test positive for the virus but do not have symptoms infected or have they mounted an effective immune response, primarily T-cell mediated? Do truly asymptomatic individuals shed adequate viral loads to infect others? There is interesting evidence that so-called asymptomatic patients manifest primarily a T-cell mediated immune response and do not produce significant antibodies, even though successful in preventing symptomatology. This is consistent with the immune response to other viral infectious diseases.

It is important to be honest and rational about the potential for a vaccine, and the real-world barriers of vaccine development, safety, ethics, economics and effectiveness. A critical issue is that we do not know if antibody-based immunity is sustained or transient in COVID-19, nor do we understand the timeframes. The evidence for long term antibody mediated immunity is inconclusive. We are also wholly lacking in the work of defining a consensus about how any of the vaccines, if successful, should be distributed, what populations in need should be prioritized and how the vaccines will be paid for. We also cannot rely on another panacea such as a rapidly developed, tested, approved and affordable antiviral or regime. As above, we are early in our immunologic understanding of human COVID-19 response. As stated earlier, our understanding of T-cell mediated immunity is being enhanced, and that is actually somewhat reassuring.

We are in the midst of an airborne respiratory disease epidemic that requires explicit, uniform and effective public health guidelines, regulations, funding, coordination, implementation, enforcement and follow up. COVID-19 needs to be suppressed and contained.

COVID-19 kills people at all ages and in all socioeconomic and ethnic groups. The fact that initially most of the cases and deaths were in the elderly and those with socioeconomic disadvantages and clinical co-morbidities, is due to its moderate infectivity. At low population penetration rates, referred to as prevalence, the disease appeared to be killing only the elderly and the infirm.

Like all infectious diseases, however, given a large enough prevalence, in other words given a chance, COVID-19 will spread and it will kill. People assume that since co-morbidities are obvious, if someone does not have diabetes, metabolic syndrome or immune compromise, a COVID-19 infection will be mild and the course of the disease benign. There are three fallacies with this line of reasoning:

  • First, not all co-morbidities are obvious or known.
  • Second, severity of infection is often relative to severity of exposure.
  • Third, the higher the prevalence the more likely the contagion is to find susceptible individuals.

To unpack the first point, we know from every country that has had COVID-19 infections, otherwise completely health young people end up contracting the disease and dying. We see a similarly concerning pattern across all respiratory infectious diseases, where healthy individuals suddenly decompensate and go into acute respiratory distress syndrome (ARDS), where their lungs fill up with fluid, and they risk rapid progression to respiratory and multi-organ system failure and death. This is not random, despite the fact that we have not identified a distinct risk or etiology. Various mechanisms are under consideration from an acute inflammatory process, to pulmonary vascular overload, to genetic predisposition, but the outcome is clear. Young, otherwise healthy individuals can contract COVID-19 and die. The greater the prevalence, the higher the number of susceptible individuals the disease will find and the more will die.

To the second point, as with other infectious diseases, the amount of virus an individual is exposed to influences both their risk of getting infected as well as the resultant severity. This is the primary driver for social distancing, use of masks, eye protection, shielding and hand hygiene. If an individual is in a setting where high levels of viral exposure are possible – indoor or outdoor, inadequate ventilation, close contact less than one meter for greater than 10-15 minutes, their infection risk is high regardless of their lack of health risk factors. In settings where all of these risks are combined and the period of exposure is prolonged or with multiple infected individuals, the risk becomes geometric. This is precisely the scenario in bars, clubs and private parties. The intent of these venues and events is to get close to people, spend time with them, talk effusively, congregate in tight groups, socialize across groups and be intimate.

To the third point, the higher the prevalence of infection in the population an individual interacts with, the higher their risk of infection, again regardless of their lack of health risk factors. This is precisely why we see the disease appear to attack a broader swath of the population across a younger age demographic as case numbers rise.