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  • Omie Mills, M.D.

COVID-19 (Part 1): Knowledge to prevent or minimize infection


2020 has been an unusually difficult year for most. COVID-19, in particular, has contributed to the physical, mental, spiritual, social, and political tensions in many lives. Members of my immediate family have been directly affected with the illness. In response, I began to research the scientific literature on this topic, as I believe that part of the stress of COVID-19 comes from a lack of understanding of the coronavirus that causes COVID-19 and from a lack of awareness of how to prevent or minimize infection.

In this blog, we will learn more about COVID-19 and how it compares to other illnesses such as the flu, what symptoms might indicate COVID-19, what type of testing is available, how to avoid an infection, the various courses an infected individual may take, and how the immune system responds.

What is COVID-19?

COVID-19 is a respiratory illness caused by the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) which is a type of coronavirus that infects people in many different ways.

Coronaviruses are a large family of viruses that have been around for a long time. Seven known types of these viruses can infect people. The coronavirus that causes COVID-19 has probably been around for some time as well, but is thought to have recently crossed over from animals into people and was discovered by scientists in 2019 (1).

Some believe that SARS-CoV-2, the virus that causes COVID-19, was being developed as a biological weapon in a lab in Wuhan, China, and that a laboratory worker was infected, from which it spread to others, though a defense expert, Dr. Mark Kortepeter, a physician and biodefense expert who formerly worked at the U.S. army “hot zone” research lab, suggests SARS-CoV-2 lacks sufficient properties to make it a good choice for military purposes (see the link below for more information).

What symptoms might I have if I am infected with SARS-CoV-2?

The Centers for Disease Control (CDC) reports that “Infected people have had a wide range of symptoms reported – from mild symptoms to severe illness. Symptoms may appear 2-14 days after exposure to the virus" (2).

People with these symptoms may have COVID-19: (2)

Fever or chills


Shortness of breath or difficulty breathing


Muscle or body aches


New loss of taste or smell

Sore throat

Congestion or runny nose


Nausea or vomiting

If someone is showing any of the following emergency warning signs, seek emergency medical care immediately:

Trouble breathing

Persistent pain or pressure in the chest

New confusion

Inability to wake or stay awake

Bluish lips or face

How do people get infected with SARS-CoV-2 that causes COVID-19?

The coronavirus that causes COVID-19 can be inhaled on droplets or as virus particles that have come from an infected person that releases the virus into the air when breathing, speaking, coughing, sneezing, or singing. This occurs more when that person is not wearing a face mask (3, 4, 5, 6, 7, 8).

In other cases, you may touch something that has coronavirus on it, and then infect yourself with the virus by touching your face. If you are living with someone who has COVID-19, your risk of becoming infected is much higher (9).

What can I do to prevent myself and others from being infected with the SARS-CoV-2 that causes COVID-19?

University of California San Francisco infectious disease specialist Peter Chin-Hong, MD likes the “Three W’s to ward off COVID-19:” wearing a mask, washing your hands, and watching your distance.10 “There’s little evidence that fomites (contaminated surfaces) are a major source of transmission, whereas there is a lot of evidence of transmission through inhaled droplets, said Chin-Hong” (10).

While washing your hands and watching your distance are generally less debated, the wearing of masks to prevent infection has become a political issue rather than a scientific one, “pitting those willing to follow health officials’ guidance and cover their faces against those who feel it violates their freedom or buys into a threat they think is overblown” (11). An initial shifting of federal recommendations have muddied the water.

Scientific studies support that “Masks are primarily intended to reduce the emission of virus-laden droplets (“source control”), which is especially relevant for asymptomatic or presymptomatic infected wearers who feel well and may be unaware of their infectiousness to others, and who are estimated to account for more than 50% of transmissions” (12, 13). So masks help to prevent virus-laden respiratory droplets from an infected asymptomatic or symptomatic wearer from reaching others. Masks also help reduce inhalation of these droplets by the wearer (“filtration for personal protection”) (14).

“My mask protects you, your mask protects me.” Unknown

Masks reduce transmission of the virus through both mechanical filtration and electrostatic filtration (15). Human studies of masking and transmission of SARS-CoV-2 show reduced transmission of 70-79% within households containing both infected and non-infected persons, and during high-risk exposures (16, 17, 18, 19, 20). “Universal masking” studies in communities showed a significant decrease in new infections, and reductions in mortality (21, 22, 23, 24, 25, 26, 27). Masking may also reduce the dose of virus the wearer might receive, resulting in a mild or even asymptomatic infection. Larger viral doses result in a more aggressive inflammatory response (28). It is important to note that openings and gaps found around the edge of the mask and facial contours can degrade the performance of the mask (29).

What type of mask should I wear to prevent infection with SARS-CoV-2?

Peter Chin-Hong, MD notes the bottom line is any mask that covers the nose and mouth will be of some benefit. “The concept is risk reduction rather than absolute prevention,” said Chin-Hong.

“You don’t throw up your hands if you think a mask is not 100 percent effective. That’s silly. Nobody’s taking a cholesterol medicine because they’re going to prevent a heart attack 100 percent of the time, but you’re reducing your risk substantially” (10).Peter Chin-Hong, M.D.University of California San Francisco Infectious Disease Specialist

A study of cloth masks suggests that cloths with high threads-per-inch such as cotton, natural silk, and chiffon provided the best protection from aerosol particles (15).

Can wearing a mask hurt me? Am I in danger of breathing in too much carbon dioxide from wearing a mask?

Fresh air is a well known booster of immunity and health, and should be sought after at every available opportunity. But in cases of close contact with potentially infected air, the slightly less than fresh air found inside of a mask will usually be less hazardous to the wearer than catching COVID-19.

Of note, however, some adverse effects have been reported by healthcare workers who have had to wear N95 masks for prolonged periods of time (i.e. headaches, acne, rash, impaired cognition) (30), and some studies have shown that some people may experience a decrease in oxygen or increase in carbon dioxide when wearing an N95 mask (31, 32). But will the effects be the same in a cloth mask?

The size of pores in varying types of masks should be better understood in order to draw more accurate conclusions. For consideration, it is important to know that the coronavirus is 0.12 microns in diameter. The N95 mask protects down to 0.1 microns with 95% efficiency and is where it gets its name (33). A surgical mask has a 0.3 – 10 micron pore sizes, which is much larger than the coronavirus (34). Cloth masks vary in pore shape and mean pore size, and in one study, the sizes of pores in cloth masks ranged from 81 to 461 microns (35).

Though it sounds as though the pore size in both surgical and cloth masks would not be able to protect you from the virus, in everyday settings, it is important to know that the virus doesn’t travel alone. COVID-19 viruses are usually carried around by respiratory droplets (36). Studies have shown that non-N95 masks including cloth masks can block these droplets effectively (but not entirely) (4, 5, 6, 7, 8). Distance from the infected person must also be considered as the concentration of aerosols is in highest concentration close to infected persons and dissipates with distance (37). Thus the importance of following the additional recommendation to remain six feet or more apart from others is better understood.

While considering the size of particles that may pass in and out of cloth masks, for the healthy mask wearer, dangerously low levels of oxygen or high levels of carbon dioxide are unlikely. If we consider size again, the coronavirus that causes COVID-19 is about 0.12 microns in diameter (33). A molecule of carbon dioxide is approximately 0.00033 microns wide and oxygen is almost the same (36). This is approximately 1000 times smaller than the coronavirus. “To help us picture the difference, let’s estimate that the period you see at the end of this sentence is about 1 millimeter wide. If we pretend the period represents a molecule of oxygen or carbon dioxide, then the virus would be about the size of a meterstick!” One meter stick is approximately 39 3/8 inches long or over 3 feet. The N95 mask, using the same scale would have just small enough pores to block 95% of the meter sticks, but could not stop the period-sized oxygen and carbon dioxide from passing in and out. But because coronavirus travels on respiratory droplets, much larger than the virus alone (36), cloth masks help prevent the spread of COVID-19. Non-N95 masks have been shown to prevent infection in 70-79% of wearers or to decrease the viral load taken in by the mask wearer (16, 17, 18, 19, 20).

How is COVID-19 similar to or different than the usual flu (influenza)?

Similarities (38):

  • Similar presentation – Both influenza and COVID-19 cause respiratory disease with illnesses ranging from asymptomatic or mild to severe disease and death.

  • Transmission – Both viruses are transmitted by contact, droplets, and fomites (objects on which the virus is located such as countertop, door knob, etc.)

  • Hand hygiene and good respiratory etiquette (coughing into an elbow or preferably a tissue) can help prevent both infections.

Differences (38):

  • Loss of smell (anosmia) or taste (ageusia) – COVID-19 sometimes causes these symptoms. The flu does not usually affect a person’s sense of smell or taste (39).

  • Time from infection to symptoms – Influenza has a shorter time from infection to the appearance of symptoms (1-4 days) (40), compared to COVID-19 (2-14 days) (41).

  • Speed of transmission – Influenza can spread to other people faster (3 day serial interval) than COVID-19 (5-6 day serial interval). Serials interval refers to the time between successive cases in a chain of transmission (42).

  • Children – are more likely to pass on influenza than COVID-19.

  • Disease severity – In COVID-19, 80% are mild or asymptomatic, 15% have severe infection, 5% have a critical infection requiring intubation. Influenza does not show as many severe or critical infections as COVID-19.

  • At risk – Those most at risk for a severe influenza infection include children, the elderly, pregnant women, the immunosuppressed, and those with underlying chronic diseases. Those at risk for COVID-19 include those of older age and those with underlying chronic diseases.

  • Mortality – COVID-19 appears to have higher mortality rates than for influenza. The data continues to change as the confirmed numbers of cases and deaths due to COVID-19 are reported, and can be followed at the following link:

At the time this paper is being written, the case mortality rate for COVID-19 in the United States is 1.8%. Mortality for seasonal influenza is below 0.1% (38). From these numbers, we can ascertain that COVID-19 is approximately 18 times more deadly than the flu, though this especially applies to those with higher risk factors such as underlying chronic disease and advanced age.

When should I check to see if I am infected with SARS-CoV-2 that causes COVID-19?

If you have reason to believe you have been exposed to someone with COVID-19 or are experiencing similar symptoms, you may need to be tested for COVID-19.

See the link below for the Mayo Clinic Self-Assessment test (43) to determine if you should be tested:

What type of tests are available to determine if I am positive for the SARS-CoV-2 virus which causes COVID-19?

There are several types of tests to determine if you are infected with the coronavirus that causes COVID-19 (44).

  1. Antigen test: This test uses a nasal or throat swab to tests for virus antigens. Results can be obtained in minutes. However, there is a risk of false negative tests with this method, meaning some people may test negative who are really positive for the coronavirus virus that causes COVID-19.

  2. PCR test: This test uses a nasal or throat swab or saliva sample to detect viral genetic material. This test is very accurate, but results may be available in minutes if analyzed on site, or may take a few days if the specimen has to be sent to another location to be processed

  3. FluSC2 Multiplex Assay: This test is a type of PCR test (see above) that can detect the genetic material of 3 different viruses that may cause similar symptoms: SARS-CoV-2 that causes COVID-19, Influenza A, and Influenza B

What does it mean if I am positive for SARS-CoV-2?

If you test positive for SARS-CoV-2, you may have been exposed to the virus causing COVID-19, though some tests detect more than one type of virus, or you may have a “false positive” test. If you are experiencing COVID-19-like symptoms, a positive test is more likely to be correct.

How long does it take for symptoms to develop if I am infected with SARS-CoV-2?

The average time until symptoms occur is 5 to 6 days. However, COVID-19 symptoms can start as early as 2 days or take up to 14 days to begin after exposure (45).

What might I expect if I develop COVID-19?

For people who develop COVID-19 symptoms, the course of the infection can vary widely. Of note, some people with COVID-19 have no symptoms yet can infect others (46). Up to 75-80% of diagnosed cases are asymptomatic (estimated to be 40% of cases) or have mild to moderate symptoms (estimated to be 35-40% of cases) that last for one to two weeks (46, 47). For those with mild to moderate cases, CDC guidelines denote that you should wait 10 days after symptoms started, and go 24 hours with no fever before heading back to work and/or out of quarantine (48).

Other cases may start mildly, but between days 5-9 may develop severe symptoms (approximately 20% of cases, or one out of every six infected persons) (49, 50). During these days, some patients will develop shortness of breath, pneumonia, or other respiratory problems. Some develop skin rashes similar to frost bite. Let your doctor know if you are getting worse. In the second week of the illness, those who have gotten worse may require hospitalization and critical care. Severe cases may require 3-6 weeks before symptoms get better. For those with severe infections, the CDC recommends waiting 20 days after symptoms started, and 24 hours with no fever before heading back to work and/or out of quarantine (51).

In the worst case scenario (in 3-4% of cases) (38), severely ill/hospitalized patients will not recover and may die within 2 – 8 weeks.

While patients who recover from COVID-19 will usually have resolution of all their symptoms, in unusual cases, some patients report having symptoms for months, including chest pain, joint pain, cough, shortness of breath, nausea, heart palpitations, and loss of taste and smell (52).

Why do some people get worse, while other get better sooner?

People at risk:

The risk of developing a serious COVID-19 infection increases with older age (80% of deaths have been in people age 65 and older), lung problems (COPD, lung cancer, cystic fibrosis, pulmonary fibrosis, moderate to severe asthma), chronic kidney or liver disease, heart disease, diabetes, and obesity (which reduce the efficiency of a person’s immune system) (53). Diabetes is known to increase the risk of infections in general. Cancer and certain blood disorders (sickle cell anemia, thalassemia) are also associated with the risk of developing more severe illness from COVID-19 (53). Additional conditions include those that would weaken the immune system (organ transplants, cancer treatments, HIV/AIDS, long term use of prednisone).

Role of the immune system:

Of note, the coronavirus that causes COVID-19 is relatively new and is not fully understood as of the date of this writing. However, we do know that when someone is first infected with a virus, that the innate (also known as the non-specific) immune system is the first part of our immune system to respond, and it is activated rapidly. The innate immune system contains physical, chemical, and cellular defenses against non-self pathogens. Immune cells detect the virus as foreign to the body. They start making cytokines (cell signaling messengers) to stop the virus. Some cytokines kill cells to stop viral replication (54). The innate immune system is very strong in young people, but weakens with age.

The other component of our immune system is the adaptive (also known as the specific) immune response which is directed against a distinct pathogen. The adaptive immune response grows stronger with age. If the virus gets past your innate immune system, adaptive immunity is your second line of defense. “B cells generate antibodies, and T cells help B cells make antibodies and can kill viruses themselves. If everything goes well, you will kill the virus and you will develop some immunity to it” (54).

Particularly important in coronavirus infections is a cytokine named interferon, a type of cytokine that promotes both the innate and adaptive immune responses, signaling or instructing the immune system that germs are present and triggering a response to the invaders. Interferons interfere with viral replication, contributing to the resolution of the infection (55). In the 1980’s, Higgens et al. (56) showed the protective effect of interferon in respiratory coronavirus, including decreased severity of symptoms and lowered viral load. Interestingly, various members of the coronavirus family can inhibit interferon production, with more aggressive coronaviruses (MERS-CoV and SARS-CoV) having a more marked inhibition of interferon activity (57, 58). Clinical studies of SARS-CoV-2 that causes COVID-19 found that a number of patients with severe COVID-19 had impaired interferon activity (59). Some of these cases were potentially linked to autoantibodies against interferon (60). Additionally, studies have found that some people have mutations in the interferon gene (61). These are a few of the possible reasons why some people have more severe infections with COVID-19 than others.

In Part II of this blog (hopefully soon to follow), ways to optimize the immune system to fight off the virus that causes COVID-19 will be discussed. Because known exposures to COVID-19 may incite unexpected quarantine and the development of possible illness, a list of things to have at home in case of infection will be noted. Ways to help house-bound friends or family if they develop COVID-19 will also be considered.

All in all, my prayer is that we will each draw closer to God and learn to trust Him more, and that as we gain knowledge through study and/or through personal experiences, we will know Him more, and be better enabled to help others befriend Him, the Author of life, the Creator of health, and our Savior.

“Beloved, I wish above all things that thou mayest prosper and be in health, even as thy soul prospereth.”3 John 1:2


  1. How Many Coronavirus Strains are There? Novel Coronavirus Types and More (


  3. Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering | NEJM

  4. Respiratory virus shedding in exhaled breath and efficacy of face masks | Nature Medicine

  5. Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US | Health Affairs

  6. (PDF) Association of country-wide coronavirus mortality with demographics, testing, lockdowns, and public wearing of masks (Update June 15, 2020). (

  7. Lack of COVID-19 transmission on an international flight | CMAJ

  8. Masks get credit for protecting a conservative community from coronavirus – The Washington Post


  10. Still Confused About Masks? Here’s the Science Behind How Face Masks Prevent Coronavirus | UC San Francisco (


  12. Moghadas SM, Fitzpatrick MC, Sah P, et al. The implications of silent transmission for the control of COVID-19 outbreaks. Proc Natl Acad Sci U S A. 2020;117(30):17513-17515.10.1073/pnas.2008373117. icon

  13. Johansson MA, Quandelacy TM, Kada S, et al. Controlling COVID-19 requires preventing SARS-CoV-2 transmission from people without symptoms. submitted. 2020.

  14. Scientific Brief: Community Use of Cloth Masks to Control the Spread of SARS-CoV-2 | CDC


  16. Wang Y, Tian H, Zhang L, et al. Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China. BMJ Glob Health. 2020;5(5).10.1136/bmjgh-2020-002794. icon.

  17. Doung-Ngern P, Suphanchaimat R, Panjangampatthana A, et al. Case-Control Study of Use of Personal Protective Measures and Risk for Severe Acute Respiratory Syndrome Coronavirus 2 Infection, Thailand. Emerg Infect Dis. 2020;26(11).10.3201/eid2611.203003. icon.

  18. Payne DC, Smith-Jeffcoat SE, Nowak G, et al. SARS-CoV-2 Infections and Serologic Responses from a Sample of U.S. Navy Service Members – USS Theodore Roosevelt, April 2020. MMWR Morb Mortal Wkly Rep. 2020;69(23):714-721.10.15585/mmwr.mm6923e4. icon.

  19. Schwartz KL, Murti M, Finkelstein M, et al. Lack of COVID-19 transmission on an international flight. Cmaj. 2020;192(15):E410.10.1503/cmaj.75015. icon.

  20. Freedman DO, Wilder-Smith A. In-flight Transmission of SARS-CoV-2: a review of the attack rates and available data on the efficacy of face masks. J Travel Med. 2020.10.1093/jtm/taaa178. icon.

  21. Wang X, Ferro EG, Zhou G, Hashimoto D, Bhatt DL. Association Between Universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers. JAMA. 2020.10.1001/jama.2020.12897. icon.

  22. Mitze T., Kosfeld R., Rode J., Wälde K. Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach. IZA – Institute of Labor Economics (Germany);2020.ISSN: 2365-9793, DP No. 13319. iconexternal icon

  23. Gallaway MS, Rigler J, Robinson S, et al. Trends in COVID-19 Incidence After Implementation of Mitigation Measures – Arizona, January 22-August 7, 2020. MMWR Morb Mortal Wkly Rep. 2020;69(40):1460-1463.10.15585/mmwr.mm6940e3. icon.

  24. Lyu W, Wehby GL. Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US. Health Aff (Millwood). 2020;39(8):1419-1425.10.1377/hlthaff.2020.00818. icon.

  25. Hatzius J, Struyven D, Rosenberg I. Face Masks and GDP. Goldman Sachs Research icon. Accessed July 8, 2020.

  26. Karaivanov A., Lu S.E., Shigeoka H., Chen C., Pamplona S. Face Masks, Public Policies And Slowing The Spread Of Covid-19: Evidence from Canada National Bureau Of Economic Research 2020.Working Paper 27891. icon.

  27. Chernozhukov V, Kasahara H, Schrimpf P. Causal Impact of Masks, Policies, Behavior on Early Covid-19 Pandemic in the U.S. medRxiv. 2020.10.1101/2020.05.27.20115139. icon

  28. Gandhi, M., Beyrer, C. & Goosby, E. J. Gen. Intern. Med. (2020).










  38. Coronavirus disease (COVID-19): Similarities and differences with influenza (


  40. What Is the Incubation Period for the Flu, and When Is It Contagious? (

  41. Coronavirus disease 2019 (COVID-19) – Symptoms and causes – Mayo Clinic

  42. Serial interval – Wikipedia



  45.,over%20a%20few%20days. Centers for Disease Control and Prevention. Coronavirus (COVID-19)- Symptoms of Coronavirus World Health Organization: Q&A on coronaviruses (COVID-19) American College of Physicians: The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application



  48. COVID-19 Communication Plan for Select Non-healthcare Critical Infrastructure Employers | CDC


  50. Symptoms of Coronavirus: Early Signs, Serious Symptoms and More (

  51. COVID-19 Communication Plan for Select Non-healthcare Critical Infrastructure Employers | CDC

  52. COVID-19 (coronavirus): Long-term effects – Mayo Clinic



  55. The Interferon (IFN) Class of Cytokines and the IFN Regulatory Factor (IRF) Transcription Factor Family – PubMed (

  56. Higgins PG, Phillpotts RJ, Scott GM, Wallace J, Bernhardt LL, Tyrrell DA. Intranasal interferon as protection against experimental respiratory coronavirus infection in volunteers. Antimicrob Agents Chemother. 1983;24(5):713–715. doi: 10.1128/aac.24.5.713.

  57. Siu KL, Kok KH, Ng MH, et al. Severe acute respiratory syndrome coronavirus M protein inhibits type I interferon production by impeding the formation of TRAF3.TANK.TBK1/IKKε complex. J Biol Chem. 2009;284:16202–16209. doi: 10.1074/jbc.M109.008227.

  58. Lui PY, Wong LY, Fung CL, et al. Middle East respiratory syndrome coronavirus M protein suppresses type I interferon expression through the inhibition of TBK1-dependent phosphorylation of IRF3. Emerg Microbes Infect. 2016;5(4):e39. Published 2016 Apr 20. doi:10.1038/emi.2016.33

  59. Hadjadj J, Yatim N, Barnabei L et al. Impaired type I interferon activity and inflammatory responses in severe COVID-19 patients. Science. 2020; 369: 718-724

  60. Bastard P, Rosen LB, Zhang Q, et al. Autoantibodies against type I IFNs in patients with life-threatening COVID-19. Science. 2020; 370eabd4585

  61. Q Zhang et al. Inborn errors of type I IFN immunity in patients with life-threatening COVID-19. Science DOI: 10.1126/science.abd4570 (2020).


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