A Brief Review of Epidemiology Concepts in the COVID-19 Era

Posted 7 months ago

By Diane Forster-Burke MS, RN

The WHO defines Epidemiology as “the study of the distribution and determinants of health-related states or events (including disease) and the application of this study to the control of diseases and other health problems.” (www.who.int., April, 2020)

Andy Larsen, sportswriter from the SL Tribune is using his knowledge of statistics to “pivot” his articles during this time of the pandemic when there are no sporting events to cover. He is doing an excellent job of explaining what is happening with COVID 19. He uses health department data and explains the data for Utah in comparison with other states and other countries. In his latest article (Salt Lake Tribune, 4/19/2020) he did a great job of explaining the use of R0 and Rt to describe the ability of this virus to spread and infect a community. I want to reiterate this for you so that you can be better informed about why the state and nation are so concerned with testing data. 

The “R0” (pronounced R- naught) is the measure of how many people 1 sick person can infect. An R0 of 1 means 1 sick person can infect 1 other person. This will not make a lot of people sick. An R0 of 10 means that for every single sick person, 10 people can become ill. That is a problem.  If each of these sick people can infect 10 others?  Then it spreads throughout the community. The R0 for COVID is calculated between 1.4-5.7. The R0 for Measles is 12-18.  The higher the number for R0, the bigger the problem with the spread of the disease.

The “Rt” (pronounced R-tee) measures the contagion rate over time. This measure shows us if social distancing and masks are having the desired effect to reduce the spread of the virus.  In his article from this past weekend, Larsen had a graph showing the Rt for Utah compared with other states.  Utah’s Rt was estimated at 1.12, meaning that we, in comparison with other states, are doing pretty well with our measures to reduce the spread of this infection.  The highest Rt among the states was Georgia at 1.5 and the lowest Rt was in Vermont at about 0.4. So the reduction measures that Utah has put in place have been working better than what Georgia is doing. However, there were people this past week, here and across the country, who decided that, their individual right to gather and protest the restrictions on gathering were paramount, and this may result in a higher Rt in the coming 2 weeks (presumed incubation period for COVID).

Epidemiology has historically been used to describe the distribution of disease in a population, but more recently, this science has also been used to describe “determinants of health”, which include: access to health care, access to clean water and air, access to healthy food, and the  ability to  exercise to improve health.  Some of these measures can be used to answer the question “Why are people of color having worse outcomes (mortalities) with COVID 19 than Anglos?”  If we think in terms of where people live, access to health care, aspects of employment, then we can think in terms of what is the predisposition toward worse outcomes. Do people have employment that provides a living wage? Do people have employment with sick leave as a part of their employment? Do people have access to healthy food in their local grocery stores? Do people have access to clean water and air?  If we think of individuals living in the Navajo Nation, they often are living in poverty; have to travel great distances for health care; do not have easy access to healthy food; and they are genetically predisposed to diabetes.  People living in poor areas of a city also may lack access to health care; lack healthy food in groceries stores that have moved to the suburbs and been replaced by convenience stores and liquor stores; and their employment situations pay a lower wage and/or do not offer a full time position so they must work additional jobs to pay for their living expenses.  These are important ways to understand determinants of health.

I hope that this write up is of interest to you. Stay home and stay safe.

A Larsen, Salt Lake Tribune, 4/19/2020.
www.who.int accessed April 20, 2020.