1.3 Challenges of managing the disease in the human population
The graphical abstract from Li et al. 2020
, showing general features of SARS-CoV-2, current knowledge of molecular immune pathogenesis, and diagnosis methods of COVID-19 based on present understanding of SARS-CoV and MERS-CoV viral infections
COVID-19 has presented numerous societal challenges, from supply line interruptions and economic sagging to overwhelmed healthcare systems and civil disorder. However, these are largely the social, economic, and political ripple effects of a disease that has brought with it a set of inherent attributes that make it more difficult to manage in human populations than say the flu.
However, COVID-19 is not the flu, and it is indeed worse in its effects than the flu, contrary to many people's perceptions. Yes, COVID-19 and the flu have some symptom overlap. Yes, COVID-19 and the flu have some transmission type overlap. But from there it diverges. COVID-19 is different in that it is more prone to be transmitted to others during the presymptomatic phase. The disease may also be transmittable in other ways, such as an airborne route, though research is ongoing. Hospitalization rates are higher, perhaps up to 10 times higher than the flu, and hospital stays are longer with COVID-19. People are dying more often from COVID-19 too, up to 10 times more often than people stricken with the flu. And of course, whereas people have been acquiring the flu vaccine yearly, limiting the percentage of the population that becomes ill, there is yet no vaccine for COVID-19, meaning everyone is susceptible.
Other aspects of the disease that make this difficult to manage include:
- Median incubation period: According to research published in Annals of Internal Medicine, the median (i.e., the central tendency, which is less skewed than average) incubation period is 5.1 days, with 97.5% of symptomatic carriers showing symptoms within 11.5 days. The authors found this to be compatible with U.S. government recommendations of monitored 14-day self-quarantines if individuals were at risk of exposure. However, many people continue to not take self-quarantines and other forms of social distancing seriously, and presymptomatic (and asymptomatic) carriers are thus more prone to spreading the virus.
- Presymptomatic and asymptomatic virus shedding: As mentioned in the previous point, carriers can be contagious during the presymptomatic phase of the disease, even while remaining symptom-free. This contagion is a result of what's called viral shedding, when the virus moves from cell to cell following successful reproduction. When the virus is in this state, it can be actively found in a carrier's body fluids, excrement, and other sources. Depending on the virus, the virus can then be introduced to another person via those sources. In the case of COVID-19, the route of transmission is still being studied, though water droplets (from sneezes, cough, talking, etc.) and potentially even aerosolized water droplets (water droplets from the body that have become fine spray or suspension in the air) are likely sources. This initial uncertainty of transmission routes, along with mixed messages early on about masks and their effectiveness for COVID-19, makes social distancing an even stronger necessity to limit community transmission of the disease.
- Understanding of high viral loads and infectious doses: Respiratory diseases such as influenza, SARS, and MERS see a correlation between the infectious dose amount and the severity of disease symptoms, meaning the higher the infectious dose, the worse the symptoms. Similarly, viral load—a quantification of viral genomic fragments—also tends to correlate with clinical symptoms. However, we are still in the investigative stages of determining if that similarly holds true to COVID-19. Early research seem to indicate, for example, there is little difference between the viral load of those with mild or no COVID-19 symptoms and those with more severe symptoms. More research must be performed to better understand how the viral load infectious dose plays a role in transmission. Given these unknowns, social distancing, wearing masks, and other means of minimizing exposure remain the best defense against the disease.
↑ Achenach, J.; Johnson, C.Y. (29 April 2020). "Studies leave question of ‘airborne’ coronavirus transmission unanswered". The Washington Post. https://www.washingtonpost.com/health/2020/04/29/studies-leave-question-airborne-coronavirus-transmission-unanswered/. Retrieved 01 May 2020.
↑ Huang, P. (20 March 2020). "How The Novel Coronavirus And The Flu Are Alike ... And Different". NPR: Goats and Soda. https://www.npr.org/sections/goatsandsoda/2020/03/20/815408287/how-the-novel-coronavirus-and-the-flu-are-alike-and-different. Retrieved 01 April 2020.
↑ Resnick, B.; Animashaun, C. (18 March 2020). "Why Covid-19 is worse than the flu, in one chart". Vox. https://www.vox.com/science-and-health/2020/3/18/21184992/coronavirus-covid-19-flu-comparison-chart. Retrieved 01 April 2020.
↑ Kumar, V. (27 March 2020). "COVID-19 has been compared to the flu. Experts say that's wrong". ABC News. https://abcnews.go.com/Health/covid-19-compared-flu-experts-wrong/story?id=69779116. Retrieved 01 April 2020.
↑ National Water and Climate Center. "Median vs. Average to Describe Normal". U.S. Department of Agriculture. https://www.wcc.nrcs.usda.gov/normals/median_average.htm. Retrieved 01 April 2020.
↑ Lauer, S.A.; Grantz, K.H.; Bi, Q. et al. (2020). "The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application". Annals of Internal Medicine. doi:10.7326/M20-0504. PMC PMC7081172. PMID 32150748. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=PMC7081172.
↑ Pinsker, J. (19 March 2020). "What Do You Tell Someone Who Still Won’t Stay Home?". The Atlantic. https://www.theatlantic.com/family/archive/2020/03/convince-family-take-coronavirus-seriously/608356/. Retrieved 01 April 2020.
↑ Keating, S. (17 March 2020). "When The People You Love Can’t Accept That They Need To Stay Home". BuzzFeed News. https://www.buzzfeednews.com/article/shannonkeating/coronavirus-social-distancing-self-isolation-quarantine. Retrieved 01 April 2020.
↑ Jackson, A. (31 March 2020). "Police are arresting and fining people for violating social distancing orders". CNN. https://www.cnn.com/2020/03/31/us/violating-coronavirus-orders-trnd/index.html. Retrieved 01 April 2020.
↑ WFLA 8 On Your Side Staff (31 March 2020). "Hawaii police arrest visiting Tampa man for violating 14-day quarantine order". WFLA News Channel 8. https://www.wfla.com/community/health/coronavirus/hawaii-police-arrest-visiting-tampa-man-for-violating-14-day-quarantine/. Retrieved 01 April 2020.
↑ 11.0 11.1 Mandavilli, A. (31 March 2020). "Infected but Feeling Fine: The Unwitting Coronavirus Spreaders". The New York Times. https://www.nytimes.com/2020/03/31/health/coronavirus-asymptomatic-transmission.html. Retrieved 01 April 2020.
↑ 12.0 12.1 Mock, J. (26 March 2020). "Asymptomatic Carriers Are Fueling the COVID-19 Pandemic. Here’s Why You Don’t Have to Feel Sick to Spread the Disease". Discover. https://www.discovermagazine.com/health/asymptomatic-carriers-are-fueling-the-covid-19-pandemic-heres-why-you-dont. Retrieved 01 April 2020.
↑ Yuen, K.-S.; Fung, S.-Y.; Chan, C.-P.; Jin, D.-Y. (2020). "SARS-CoV-2 and COVID-19: The most important research questions". Cell & Bioscience 10: 40. doi:10.1186/s13578-020-00404-4. PMC PMC7074995. PMID 32190290. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=PMC7074995.
↑ Diamond, F. (17 March 2020). "Asymptomatic Carriers of COVID-19 Make It Tough to Target". Infection Control Today. https://www.infectioncontroltoday.com/covid-19/asymptomatic-carriers-covid-19-make-it-tough-target. Retrieved 01 April 2020.
↑ Jordan, R. (26 March 2020). "Environmental engineers at Stanford discuss how to identify factors affecting COVID-19 transmission". Stanford News. https://news.stanford.edu/2020/03/26/understanding-spread-covid-19/. Retrieved 01 April 2020.
↑ 16.0 16.1 16.2 Greenfieldboyce, N. (28 March 2020). "WHO Reviews 'Current' Evidence On Coronavirus Transmission Through Air". NPR. https://www.npr.org/2020/03/28/823292062/who-reviews-available-evidence-on-coronavirus-transmission-through-air. Retrieved 01 April 2020.
↑ Chicago Sun Times Editorial Board (31 March 2020). "Ignore the mixed messages and wear that mask". Chicago Sun Times. https://chicago.suntimes.com/2020/3/31/21200144/coronavirus-covid-19-masks-wear-cdc-pritzker-trump-public-health-virus-face-cough-sneeze. Retrieved 01 April 2020.
↑ Mulholland, J. (29 March 2020). "To mask or not to mask: mixed messages in a time of crisis". RFI. http://www.rfi.fr/en/international/20200329-to-mask-or-not-to-mask-mixed-messages-in-a-time-of-coronavirus-crisis-france-covid-19-spread-droplets. Retrieved 01 April 2020.
↑ 19.0 19.1 19.2 19.3 Geddes, L. (27 March 2020). "Does a high viral load or infectious dose make covid-19 worse?". New Scientist. https://www.newscientist.com/article/2238819-does-a-high-viral-load-or-infectious-dose-make-covid-19-worse/. Retrieved 01 April 2020.
↑ Hijano, D.R.; Brazelton de Cardenas, J.; Maron, G. et al. (2019). "Clinical correlation of influenza and respiratory syncytial virus load measured by digital PCR". PLoS One 14 (9): e0220908. doi:10.1371/journal.pone.0220908. PMC PMC6720028. PMID 31479459. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=PMC6720028.
↑ Liu, Y.; Yan, L.-M.; Wan, L. et al. (2020). "Viral dynamics in mild and severe cases of COVID-19". The Lancet Infectious Diseases. doi:10.1016/S1473-3099(20)30232-2. PMID 32199493.
↑ Joynt, G.M.; Wu, W.K.K. (2020). "Understanding COVID-19: what does viral RNA load really mean?". The Lancet Infectious Diseases. doi:10.1016/S1473-3099(20)30237-1.
↑ 23.0 23.1 Madjid, M.; Safavi-Naeini, P.; Solomon, S.D. (2020). "Potential Effects of Coronaviruses on the Cardiovascular System". JAMA Cardiology. doi:10.1001/jamacardio.2020.1286. PMID 32219363.
↑ 24.0 24.1 Xiong, T.-Y.; Redwood, S.; Prendergast, B.; Chen, M. (2020). "Coronaviruses and the cardiovascular system: acute and long-term implications". European Heart Journal: ehaa231. doi:10.1093/eurheartj/ehaa231. PMID 32186331.
↑ Driggin, E.; Madhavan, M.V.; Bikdeli, B. et al. (2020). "Cardiovascular Considerations for Patients, Health Care Workers, and Health Systems During the Coronavirus Disease 2019 (COVID-19) Pandemic". Journal of the American College of Cardiology. doi:10.1016/j.jacc.2020.03.031. PMID 32201335.
↑ 26.0 26.1 Otto, M.A. (26 March 2020). "Cardiac symptoms can be first sign of COVID-19". The Hospitalist. https://www.the-hospitalist.org/hospitalist/article/219645/coronavirus-updates/cardiac-symptoms-can-be-first-sign-covid-19. Retrieved 01 April 2020.
↑ 27.0 27.1 Clerkin, K.J.; Fried, J.A.; Raikhelkar, J. et al. (2020). "Coronavirus Disease 2019 (COVID-19) and Cardiovascular Disease". Circulation. doi:10.1161/CIRCULATIONAHA.120.046941. PMID 32200663.
↑ Mehta, P.; McAuley, D.F.; Brown, M. et al. (2020). "COVID-19: Consider cytokine storm syndromes and immunosuppression". The Lancet 395 (10229): P1033–34. doi:10.1016/S0140-6736(20)30628-0. PMID 32192578.
↑ 29.0 29.1 Mandavilli, A. (01 April 2020). "The Coronavirus Patients Betrayed by Their Own Immune Systems". The New York Times. https://www.nytimes.com/2020/04/01/health/coronavirus-cytokine-storm-immune-system.html. Retrieved 01 April 2020.
↑ Tisoncik, J.R.; Korth, M.J.; Simmons, C.P. et al. (2012). "Into the eye of the cytokine storm". Microbiology and Molecular Biology Reviews 76 (1): 16–32. doi:10.1128/MMBR.05015-11. PMC PMC3294426. PMID 22390970. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=PMC3294426.
↑ Basilio, P. (26 March 2020). "A new potential risk of COVID-19: Sudden cardiac death". MDLinx. https://www.mdlinx.com/internal-medicine/article/6590. Retrieved 01 April 2020.
↑ Rettner, R. (23 April 2020). "Mysterious blood clots in COVID-19 patients have doctors alarmed". LiveScience. https://www.livescience.com/coronavirus-blood-clots.html. Retrieved 28 April 2020.
↑ Moyer, M.W. (19 May 2020). "What We Know About the Covid-Related Syndrome Affecting Children". The New York Times. https://www.nytimes.com/2020/05/19/parenting/pmis-coronavirus-children.html. Retrieved 19 May 2020.
↑ Fischer, K. (18 May 2020). "What to Know About PMIS, the COVID-19-Linked Syndrome Affecting Children". Healthline. https://www.healthline.com/health-news/what-to-know-pmis-syndrome-linked-to-covid-19-affects-children. Retrieved 19 May 2020.
- Cardiovascular issues: Coronaviruses and their accompanying respiratory infections are known to complicate issues of the cardiovascular system, which in turn may "increase the incidence and severity" of infectious diseases such as SARS and COVID-19. While the exact cardiac effect COVID-19 has on patients is still unknown, suspicion is those with "hypertension, diabetes, and diagnosed cardiovascular disease" may be more prone to having cardiovascular complications from the disease. Current thinking is SARS-CoV-2 either attacks heart tissues, causing myocardial dysfunction, or inevitably causes heart failure through a "cytokine storm,", an overproduction of signaling molecules that promote inflammation by white blood cells (leukocytes). What's scary is that like the 1918 Spanish flu, SARS, and other epidemics, some otherwise healthy patients' immune responses are entirely overreactive, leading to acute respiratory distress syndrome (ARDS) or heart failure. Additionally, as the disease has progressed, medical professionals have noted two additional cardiovascular issues. First, an atypical amount of blood clotting has shown up in some infected patients, which may or may not be related to overreactive immune systems and underlying health conditions. Second, what is being called pediatric multisystem inflammatory syndrome (PMIS) is beginning to show up in children after the infection has passed, characterized by inflamed blood vessels and toxic shock syndrome. These uncertainties only add to the level of difficulty of properly treating COVID-19.