Brief talk by Anthony S. Fauci, M.D.
Director of National Institute of allergy and Infectious Diseases, NIH
When the novel coronavirus was discovered, the ease with which it could be transmitted among humans was unknown. SARS-CoV-2 is the third pandemic coronoavirus, following SARS-CoV-1 and MERS-CoV. The coronavirus phylogenetic tree provides an overview of the different human coronaviruses.
COVID-19 is the disease caused by the novel coronavirus, SARS-CoV-2. This has been the largest pandemic for the past 102 years. At the time of the talk, data was provided from 8/18/2020 from NPR.org and Worldometer indicating 22.2 million cases and 780,906 deaths across 215 countries/territories. CDC data from the same day was provided indicating 5.4 million cases and 169,870 deaths in the United States alone, the worst-hit country of the pandemic.
"The transmission is well known. It is a respiratory borne virus."
- Transmission between people in close contact
- Transmission via particles that remain in the air over time and distance
- Infected surfacecs
- Virus found in stool, blood, semen and ocular secretions; role in transmission unknown
- Animals (including domesticated) not major source of human infection
One thing that has been very clear with this virus that has been very troublesome and problematic is the fact that about 40-45% of individuals who are infected are without symptoms, and asymptomatic individuals have now been clearly documented to transmit the virus from person to person, making it extremely problematic with regards to tracking these infections, and to do identification, isolation, and contact tracing.
The risk of transmission varies by type and duration of exposure, viral load, and preventive measures. Infections most common in households and congregative or healthcare settings where personal protective equipment is not used, and in closed settings. There are numerous cases of social or work gatherings leading to transmission. Despite this understanding, key questions remain:
- What is the role of various types of respiratory particles in SARS-CoV-2 transmission?
- At what concentration is infectious virus contained in various types of particles?
- How is the concentration of infectious virus effected by various environmental conditions?
- What is the dose of virus needed to establish infection at various anatomic sites?
The purpose of the workshop is to help shed light on these questions.
[Our comment: this highlights the importance of paying attention to viral load in the environment. People we have spoken to often look to answer a binary question of "has XYZ been proven effective against COVID-19[sic]," but this is not the most productive question to consider -- unless you are operating some sort of bio-facility that is certified to meet certain standards and will be very expensive, you will never bring down transmission risk to 0 in real world work or social settings. Instead, the question needs to be first, what is the respective component to R0 that each transmission pathway provides? How much can we reduce the viral load on this transmission pathway?
These are both analog questions. In answering these questions it is possible to get a relative sense of improvements, but it is impossible to get exact answers. This is particular important in considering aerosol transmission compared to surfaces. Unlike surfaces that when wiped properly with a disinfectant, or when one washes one's hands after coming into contact where confidence can be above 99% within some tens of seconds, air safety is not so clearcut. Importantly, after various appropriate safety/protective measures are implemented for both fomites (surfaces) and aerosol transmission, the relative residual risk from air in a continuously occupied building will be at least an order of magnitude higher, irrespective of the relative absolute risks prior to implementing said measures. If the aerosol pathway can be effectively mitigated, then only large droplet transmission remains as a major risk, in which case some studies have shown that R0 would drop below 1, regardless of mask usage.]
The impact of this information about transmission from this workshop will impact a number of factors:
- The forcefulness with which masking requirements are implemented (should be very strong).
- The degree of ventilation that is needed for indoor environments, as well as how we clean and disinfect particles.
- The importance of physical distancing, along with transmission in healthcare settings.
See the key FAQ pages provided by a team of scientists on COVID-19 transmission and preventive approaches:
- 1. General questions about COVID-19 transmission
- 2. General questions about aerosol transmission
- 3. Protecting ourselves from aerosol transmission
- 8. Ventilation
- 9. Filtering, and “air cleaning”
Anthony S. Fauci is director of the National Institute of Allergy and Infectious Diseases (NIAID) at the U.S. National Institutes of Health, where he oversees an extensive research portfolio devoted to preventing, diagnosing, and treating infectious and immune-mediated diseases. Dr. Fauci has been a key advisor to six Presidents and their administrations on global AIDS issues, and on initiatives to bolster medical and public health preparedness against emerging infectious disease threats such as pandemic influenza. As an HIV/AIDS researcher he has been involved in the scientific effort since AIDS was recognized in 1981, conducting pivotal studies that underpin the current understanding of the disease and efforts to develop therapies and tools of prevention. Dr. Fauci was one of the principal architects of the President’s Emergency Plan for AIDS Relief (PEPFAR), which has helped save millions of lives throughout the developing world. Dr. Fauci is the long-time chief of the NIAID Laboratory of Immunoregulation. He has made many contributions to basic and clinical research on the pathogenesis and treatment of immune-mediated and infectious diseases. He helped pioneer the field of human immunoregulation by making important basic scientific observations that underpin the current understanding of the regulation of the human immune response. In addition, Dr. Fauci is widely recognized for delineating the precise mechanisms whereby immunosuppressive agents modulate the human immune response. He developed effective therapies for formerly fatal inflammatory and immune-mediated diseases such as polyarteritis nodosa, granulomatosis with polyangiitis (formerly Wegener's granulomatosis), and lymphomatoid granulomatosis. Dr. Fauci has made seminal contributions to the understanding of how HIV destroys the body's defenses leading to its susceptibility to deadly infections. Further, he has been instrumental in developing highly effective strategies for the therapy of patients living with HIV/AIDS, as well as for a vaccine to prevent HIV infection. He continues to devote much of his research time to identifying the nature of the immunopathogenic mechanisms of HIV infection and the scope of the body's immune responses to HIV. Dr. Fauci is a member of the US National Academy of Sciences and the US National Academy of Medicine, and is the recipient of numerous prestigious awards for his scientific and global health accomplishments, including the National Medal of Science, the Robert Koch Medal, the Mary Woodard Lasker Award for Public Service, the Prince Mahidol Prize, The Gairdner Canada Award for Global Health, and the Presidential Medal of Freedom. He has been awarded 45 honorary doctoral degrees and is the author, coauthor, or editor of more than 1,300 scientific publications, including several major textbooks.