Coronavirus

Many countries around the world are struggling with the question of when and how to reopen the country after lockdown.  Many, including the UK and Germany,  have come to rely on a parameter called R or R 0 as a benchmark for reopening and staying open.  What makes R so powerful?  In epidemiology, R 0 is the pathogen’s basic reproduction number and represents the number of new infections caused, on average, by a single contagious person.   R, or the effective reproduction number (sometimes designated as R e or R t ), will start at R 0 and should decline over time as the population gets infected, builds immunity, and mitigation measures are activated.   R = (1 - P) x R 0 ,    where P is the percentage of the population that is immune or out of the pool of susceptible individuals.   If 60% of the population is vaccinated or isolated then only 40% can be infected and R is only 0.4R 0 .   R 0 of the novel coronavirus has been variou...

Senator Rand Paul’s criticism of Dr. Fauci earlier this week left the impression that Kentucky solved the Pandemic problem.  On what basis did he conclude that Kentucky “never really reached any sort of pandemic levels…We have less deaths in Kentucky than we have in an average flu season.”? Kentucky has had 7080 cases of COVID-19 – with little evidence that the pandemic has slowed in May.   On a per-capita basis 0.16% of its population – including its senator - has contracted the disease.   326 Kentuckians have died from this disease or more than 73 per million of its citizens.   This compares to the 33 confirmed seasonal flu death in Kentucky this season .   This gives Kentucky a coincident case fatality rate of 4.6%, ~20 times worse than seasonal flu’s 0.24% this year.   The 4.6% measured may or may not be a good estimate given that Kentucky has only tested 2.6% of its population compared to the national average of 3.1%.   If it were a cou...

The US President was recently quoted as saying : “If we did very little testing, we wouldn't have the most cases.   So, in a way, by doing all of this testing, we make ourselves look bad,"   You have been poorly advised.   The infections are in the country whether we test or not.   Moreover, now that you have reopened the country, too quickly according to some crazy critics, everyone will get infected sooner rather than later.   The infection rate doesn’t really matter much when everyone is infected.   However, if you can test everyone that is infected you can lower the measured case fatality rate.   A lower fatality rate will make American look great again in the eyes of its own citizens and the world.   The US has a measured fatality rate of 6.0%, better than some countries in Europe but definitely worse than some of the countries lauded as best in class for managing their COVID-19 pandemics better than others: for example South Korea, ...

There has been a lot of discussion about race and other demographic differences in communities showing up as higher death rates for example for  Blacks and Hispanics .    But it is important to understand the concepts of infection rate, death rate, and mortality rate for a pandemic.   Death rates, the number of fatalities in each subpopulation divided by the number of people in each subpopulation, while stark and headline-grabbing, is not so important in terms of disease understanding and control.   It is a point in time measurement that increases monotonically as a disease progresses from zero to some large scary number.   Different communities may experience the disease at different starting points so it is often meaningless to compare this metric among different communities.   Infection rate, the number of confirmed cases divided by the number of people in each subpopulation is important and indicates how susceptible each group of people may be to a...