The epidemiological information reported by the World Health Organization (WHO), the Johns Hopkins University website, and the Centers for Disease Control (CDC) provide a limited scope of what we’ve learned about COVID-19 to date. Furthermore, some of the in-depth measures that advance our understanding of the virus’s epidemiology could use more explanation.
According to the CDC, epidemiology is defined as “the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.” The COVID-19 surveillance that we see on the WHO, CDC, and Johns Hopkins websites do a thorough job of outlining the distribution of health-related states.
Each site provides people with an interactive map of the global distribution of infections, hospitalizations, and deaths, including color-coded indexes highlighting countries, states, and counties with low to high disease burden. However, one missing factor with this way of describing disease distribution is that it falls short in conveying how we’ve transitioned from COVID distribution to controlling disease spread through changes in policy and procedure. This warrants looking at some of the higher-level measures.
Let’s begin with the most up-to-date data about COVID-19 in the United States. As of November 7, 2020, the United States has had roughly 9.7 million cases of COVID-19 since the start of the pandemic, causing 235,000 deaths. These figures enable us to determine disease severity with a common measure known as the case fatality rate (CFR).
Here, we compare the number of cases to the number of deaths. This gives us a CFR of 2.57 percent. Compare this figure to whooping cough with a CFR of at 3.7 percent or yellow fever of 7.5 percent. Note that these figures alone are inadequate as they do not account for protective factors that vary in a population such as age, vaccination status, comorbid chronic illness, and health care quality.
These factors determine the spectrum of disease severity that we’ve seen since the pandemic started. The most resilient among us, the young and healthy, have a much lower CFR than those that are older with other illnesses. This explains why nursing homes have been particularly concerning; they serve a population amongst our eldest and thus more prone to serious cases. It also provides us with part of the rationale central to the discussion about reopening schools and restrictions to visitors within hospitals and nursing homes.
The goal of controlling a pandemic requires a response at the highest level of government. In the coming months, we will see how the response from government officials changes, and what new epidemiological measures are utilized.