This COVID-19 one pager, made up by a Seattle ICU/ER doc (Nick Mark, MD) and which reads like the ultimate cheat sheet for a one hundred question exam on the virus, has been circulating among some of my medical colleagues. As a naturopathic physician, I thought I’d take a moment to draft a multi-part blog post which breaks down everything in it, with some links to studies.
Here is part 2, as promised.
- Attack Rate = 30-40% (China). Attack Rate (AR), a biostatistical concept in epidemiology, measures the frequency of morbidity, that is, the speed at which the infection spreads in at risk populations. We of course use this to predict the rate at which an infection will spread hypothetically, particularly in an epidemic such as the one we are in now. There is no way that resources can be adequately marshalled if projections are not possible. It can be determined by dividing the number of new cases in the at risk population by the total number at risk. An AR of 30-40% means that about 1/3 of the at risk population becomes infected. (1)
- R0 = 2-4. R0 or “R nought” is another epidemiological measurement: the number of cases that on average a person who is infected will cause over the duration of their infection. In other words, it’s a reproduction number. The R0 for measles ranges from 12 to 18, wherethe R0 for influenza is much lower at 2 to 3. With COVID-19, an R0 of 2 to 4 means that2 to 4 new cases will be reproduced by one infected person. (2)
- Case fatality rate (CFR) = 2.3% (China). CFR is pretty straight-forward. 2.3 out of every 100 cases will result in death. (3)
- Incubation time = 3-14 days (up to 15 days). It takes the virus 3 to 14 days to incubate. According to a March, 2020 report from The Annals of Internal Medicine, “estimates imply that, under conservative assumptions, 101 out of every 10,000 cases (99th percentile, 482) will develop symptoms after 14 days of active monitoring or quarantine.” (4)
- Viral shedding = median 20 days (max 37 days): The virus will shed, that is, release its progeny as it reproduces during host-cell infection. On average, COVID-19 infections will produce viral shedding for 20 days, but it can last as long as 5 weeks. Just to be clear, viral shedding can take place in a number of ways, such as from a single cell, from one part of the body to another part, and from body parts into the environment. (5, 6)
- Breakdown of disease severity.
- 80% Non-severe (mild pneumonia)
- 15% Severe (hypoxia, respiratory distress)
- 5% Critical (respiratory failure)
- 80% of those are infected will actually get mild pneumonia of the non-severe type but 15% will actually experience respiratory distress and low blood-oxygen saturation. 5 out of every 100 persons will experience respiratory failure, which can lead to death if not treated quickly. (7, 8)
- Disease clusters: SNFs, Conferences, other. An SNF is a step-down facility where people go to recover from surgeries or other conditions, where medically necessary services are available for in-patient rehabilitation. These are obviously high-risk places where disease clusters can preponderate, as are nursing home and other long-term care facilities.
- Strategies: contact tracing, screening, social distancing. Pretty self-explanatory. (9, 10)
- #FlattenTheCurve: same AUC but distributed over a longer time, ensuring that hospitals don’t exceed capacity.
- 65-80% cough
- 45% febrile on presentation (85% febrile during illness)
- 20-40% dyspnea
- 15% URI symptoms: Classic symptoms include cough, nasal discomfort or congestion, rhinitis, a sore throat, mucus buildup, a mild fever
- 10% GI symptoms (11)
Rothan HA, Byrareddy SN. The epidemiology and pathogenesis of coronavirus disease (COVID-19) outbreak [published online ahead of print, 2020 Feb 26]. J Autoimmun. 2020;102433. doi:10.1016/j.jaut.2020.102433
Velavan TP, Meyer CG. The COVID-19 epidemic. Trop Med Int Health. 2020;25(3):278–280. doi:10.1111/tmi.13383
Porcheddu R, Serra C, Kelvin D, Kelvin N, Rubino S. Similarity in Case Fatality Rates (CFR) of COVID-19/SARS-COV-2 in Italy and China. J Infect Dev Ctries. 2020;14(2):125–128. Published 2020 Feb 29. doi:10.3855/jidc.12600
Lauer SA, Grantz KH, Bi Q, et al. The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application [published online ahead of print, 2020 Mar 10]. Ann Intern Med. 2020;M20-0504. doi:10.7326/M20-0504
Zhang W, Du RH, Li B, et al. Molecular and serological investigation of 2019-nCoV infected patients: implication of multiple shedding routes. Emerg Microbes Infect. 2020;9(1):386–389. Published 2020 Feb 17. doi:10.1080/22221751.2020.1729071
Young BE, Ong SWX, Kalimuddin S, et al. Epidemiologic Features and Clinical Course of Patients Infected With SARS-CoV-2 in Singapore [published online ahead of print, 2020 Mar 3]. JAMA. 2020;e203204. doi:10.1001/jama.2020.3204
Sun P, Lu X, Xu C, Sun W, Pan B. Understanding of COVID-19 based on current evidence [published online ahead of print, 2020 Feb 25]. J Med Virol. 2020;10.1002/jmv.25722. doi:10.1002/jmv.25722
Li YC, Bai WZ, Hashikawa T. The neuroinvasive potential of SARS-CoV2 may play a role in the respiratory failure of COVID-19 patients [published online ahead of print, 2020 Feb 27]. J Med Virol. 2020;10.1002/jmv.25728. doi:10.1002/jmv.25728
Stein R. COVID-19 and Rationally Layered Social Distancing [published online ahead of print, 2020 Mar 14]. Int J Clin Pract. 2020;e13501. doi:10.1111/ijcp.13501
Wilder-Smith A, Freedman DO. Isolation, quarantine, social distancing and community containment: pivotal role for old-style public health measures in the novel coronavirus (2019-nCoV) outbreak. J Travel Med. 2020;27(2):taaa020. doi:10.1093/jtm/taaa020
Zu ZY, Jiang MD, Xu PP, et al. Coronavirus Disease 2019 (COVID-19): A Perspective from China [published online ahead of print, 2020 Feb 21]. Radiology. 2020;200490. doi:10.1148/radiol.2020200490