Many people and news sources have been saying, recently, that people should worry about flu more than novel Coronavirus (CV), citing that tens of thousands of people die from flu every year-- while CV remains far fewer... and no one in the US has died from CV, as of this date. I heard a radio talk show host, today, say, “In the grand scheme of things, it just seems like such a miniscule issue.” The reasons it is NOT miniscule are:
· Between 50 and 400 times as many people with CV will be hospitalized compared to the same number of patients with flu (~20% instead of 0.05-0.37%), and hospitalizations will last 2-5 times as long (2 weeks instead of 3-7 days).
· At the currently publicized fatality rates, 23 times more CV patients will die as flu patients (2.3% instead of 0.1%).
· CV spreads more readily. The R0, or number of people infected by a single sick patient, is higher for CV than for flu. Seasonal Flu R0 is 2 to 3, and CV R0 is as high as 4.7 to 6.3 prior to containment, and 2-3 after “vigorous control measures.” The World Health Organization estimates the CV R0 as 2-2.5, but the effective number is for the entire outbreak, which includes during control measures. Note that even with “vigorous control measures,” the R0 for CV compares to the regular R0 of flu.
· Approximately 81% of CV infections are “mild, meaning they did not result in pneumonia or resulted in only mild pneumonia,”. While the 19% with more than mild pneumonia are not specifically stated as requiring hospitalization, for the purposes here, I will speculate that folks with more than mild pneumonia require hospitalization. I'll also treat the number as a round 20% for convenience.
The length of stay in hospital is unrelated to the quarantine / gestation period. It is purely coincidental that they are both about two weeks.
· Approximately 10 to 50 M people have gotten the flu each year since 2010. The CDC reference actually says 9.3 to 49 M, but I will use round numbers to make for easy math.
· For each 100,000 flu cases, 49 to 370 people (or 0.05% to 0.37%) are hospitalized.
If CV is contracted as much as flu (10-50 M per year):
· CV would be expected to produce fatalities of 0.23M to 1.15M.
· The number of people needing hospitalization in the US would be 2M to 10M.
· Consider the number of hospitalizations multiplied by the length of stay; calculating the “person days in the hospital” or hospital load factor:
Flu: Number of hospitalizations times length of stay = (10 to 50 M cases per year) * (.05 to 0.37% hospitalizations per case) * (3 to 7 days per hospitalization) = 15,000 to 1,295,000 “person days in the hospital.”
CV: Number of hospitalizations times length of stay = (10 to 50 M cases per year) * 20% hospitalizations per case * 14 days per hospitalization = 28,000,000 to 140,000,000 “person days in the hospital.”
If more people get CV than get flu, which seems quite possible without containment-- given the lack of acquired immunity and no vaccine and the reported R0--, then more than the numbers above could result.
The 20% “serious cases” and 2.3% fatality rate are enough to raise concern, along with a higher hospital load than flu due to the length of the illness, which explains why the CDC is talking about “Non Pharmaceutical Interventions” (NPIs) such as closing schools and businesses. The only way to keep the hospital load and fatality rate down is to keep the case rate down. It is why China quarantined Wuhan. It is the only way to avoid a catastrophe. “Containment” is the only option.
The question remains, then, “How many people will get it?” Containment in America has ostensibly been slowed considerably by President Trump’s early decision to disallow entry of foreign travelers who had been in China. Yet, the CDC predicts that the slowing will not prevent the spread within the US, merely slow it. Delay is of considerable importance, especially given the “hospital load factor” discussed above. Harvard epidemiology professor Marc Lipsitch predicts that within the coming year, some 40 to 70 percent of people around the world will be infected with the virus that causes COVID-19.
There are 7.8 billion people in the world and 330 million people in America.
40 to 70% people infected: 3.12 to 5.46 B cases
2.3% fatality of cases: 72 to 126 M deaths
40 to 70% people infected: 132 to 231 M cases2.3% fatality of cases: 3.0 to 5.3 M deaths
The WHO reports that the fatality rate was as high as 17.3% early in the outbreak, reduced as low as 0.7% as “standard of care has evolved.” Certainly, it makes sense that a learning curve would be involved in clinical care of patients. If the fatality rate can be reduced to 0.7% around the world, the number of deaths in the preceding paragraph could be reduced by over two thirds. The other way to reduce fatalities is, obviously, to reduce the number of cases. That is why “NPIs” are to be expected.
People really need to stop using the flu comparison to try to make themselves feel safe. The comparison to the flu is NOT comforting.
 Eisenberg, Joseph, The Conversation, University of Michigan School of Public Health, https://sph.umich.edu/pursuit/2020posts/how-scientists-quantify-outbreaks.html, accessed February 27, 2020.
 Sanche, Steven, The Novel Coronavirus, 2019-nCoV, is Highly Contagious and More Infectious Than Initially Estimated, https://www.medrxiv.org/content/10.1101/2020.02.07.20021154v1.full.pdf, accessed February 27, 2020.
 World Health Organization, Report of the WHO-China Joint Mission on Coronavirus Disease 2019 (COVID-19), https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf, accessed February 28, 2020.
 Soucheray, Stephanie, Study of 72,000 COVID-19 patients finds 2.3% death rate, Center for Infectious Disease and Research Policy, http://www.cidrap.umn.edu/news-perspective/2020/02/study-72000-covid-19-patients-finds-23-death-rate, accessed February 27, 2020.
 Ibid, Sanche.
 Thompson, William W., Influenza-Associated Hospitalizations in the United States, https://jamanetwork.com/journals/jama/fullarticle/199440, accessed February 27, 2020.
 Ibid, Soucheray.
 Ibid, Center for Disease Control.
 Ibid, Thompson.
 Centers for Disease Control, Transcript for Press Briefing, February 25, 2020, https://www.cdc.gov/media/releases/2020/t0225-cdc-telebriefing-covid-19.html, accessed February 27, 2020.
 Hamblin, James, “You’re Likely To Get the Coronavirus,” https://www.theatlantic.com/health/archive/2020/02/covid-vaccine/607000/, accessed February 28, 2020.
 Ibid, World Health Organization.