Masks, Contagion and Getting Back to Work
It is hard to believe that August is around the corner, marking the 6th month that we have spent in the COVID-19 pandemic. Unfortunately, we are not where we hoped we would be, with many states continuing to see rising in case counts, hospitalizations, and deaths. We are still in the “pre-protection” phase of the pandemic – no vaccine, no effective antivirals, and no herd immunity, which leaves mask mandates and social distancing as our only defenses. The rising case counts have stressed not only healthcare systems but also our testing capacity, with turn-around times for test results approaching two weeks in some of the harder-hit areas. For this week’s COVID-19 corner, we will highlight what we think is pertinent right now.
Many states have issued mask mandates (our home state of Ohio included, albeit after a fashion), and those that have not should get on board. There are evidence supporting SARS-CoV-2 transmission while presymptomatic or asymptomatic (https://wwwnc.cdc.gov/eid/article/26/7/20-1595_article), which is felt to be a driver of community transmission and acceleration of the pandemic. A study examined temporal patterns of viral shedding in 94 patients with COVID-19 and observed the highest viral load in throat swabs at the time of symptom onset, and estimated that 44% of secondary cases were infected during the index cases’ presymptomatic stage (https://www.nature.com/articles/s41591-020-0869-5). These data support continued vigilance for social distancing and universal masking, and that case finding should include isolation and tracking of contacts during the presymptoamtic phase.
Along these same lines, a study analyzed reports for 59,073 contacts of 5,707 COVID-19 cases reported in South Korea over a 9-week period, and grouped index patients by age (https://wwwnc.cdc.gov/eid/article/26/10/20-1315_article). SARS-CoV-2 was detected in 11.8% of household contacts, and rates were higher for contacts of children compared to adults, with the highest number of positive household contact occurring from exposure to index patients aged 10-19 years. This highlights another important topic that has been the center of much discussion – is SARS-CoV-2 transmissible via airborne or droplet route. I think we can all agree that SARS-CoV-2 most likely aerosolizes in certain settings like during invasive procedures, however, SARS-CoV-2 is not an airborne infection. This South Korean study highlights the household attack rate of COVID being ~ 11%. Household attack rates for airborne viruses like measles and varicella are upwards of 90% – very different from that of SARS-CoV-2 and reinforcing that the main mode of transmission is via droplet spread.
Lastly, criteria for ending isolation and returning to work after recovering from COVID-19 infection continue to be a work in process, with the CDC updating recommendations again last week –changing the requirement for the symptom-based criteria from “at least 72 hours” to “at least 24 hours” have passed since last fever without the aid of fever-reducing agents (https://www.cdc.gov/coronavirus/2019-ncov/hcp/disposition-in-home-patients.html). They have also changed the second piece of the recommendation from “improvement in respiratory symptoms” to “improvement in symptoms” to address the ever-growing list of COVID-19 symptoms and to include patients who never even develop respiratory symptoms. We find this shortened afebrile period to be a bit gung-ho, realizing that many people do not even know when they have a fever, and thus this requirement will be dependent on patients diligently monitoring their fever over a 24-hour period, which may not always be feasible.
We will continue sharing our COVID-19 thoughts with you every two weeks instead of weekly, and hope to have something positive to discuss two weeks from now. In the meantime, please give us a shout out with thoughts or questions!
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Leonard H. Calabrese, DO, is the head of the RJ Fasenmyer Center for Clinical Immunology and Vice-Chair of the Department of Rheumatic and Immunologic Diseases at Cleveland Clinic Dr. Calabrese has lectured nationally and internationally on the subjects of immunology, rheumatology, and viral diseases. He is the author of more than 400 published peer-reviewed articles, book chapters, and reviews. @LCalabreseDO
Cassandra Calabrese, DO, is a staff physician in the Department of Rheumatic and Immunologic Diseases and the Department of Infectious Diseases at Cleveland Clinic and directs the combined Rheumatology-Infectious Disease training program. She also directs the Clinic for immune-related adverse events form cancer immunotherapy within the department of Rheumatic and Immunologic Diseases. @CCalabreseDO