Stopping the Silent Spread

Asymptomatic and mild cases play an important role in the infectious disease epidemiology–they silently spread disease. Infectious disease epidemiology largely involves focusing on preventative factors. Generally, this is done in two steps:

Investigate the factors underlying how exposure to an infectious pathogen took place. Implement preventative measures to slow or stop disease spread based on exposure factors.

When hospitals begin to treat numbers of severe cases of an infectious disease, it is a sign that preventative efforts have not been effective. Because of the United States’ failure to broadly test suspected cases of COVID-19 in the early stage of the outbreak, it has now spread widely. Worse, choosing to test only severe cases while ignoring non-severe cases enables the virus to spread rapidly. This approach is wrongly adopted because of a misunderstanding of the purpose of testing, which is not only to clinically diagnose individual patients, but to epidemiologically control community spread.

According to many credible estimates, the U.S. is likely only 10 days behind Italy in its COVID-19 caseload. We must put aggressive preventative measures in place now to reduce the numbers of severe cases.

The Bigger Picture

In 1981, epidemiologist Geoffrey Rose explained, “a large number of people exposed to a small risk may generate many more cases than a small number exposed to a high risk.” He termed this concept the “prevention paradox.”

The message we hear from public officials and many media sources is that, for most people, the risks associated with COVID-19 are low. But this does not present a full picture of the risk to society at-large. First, the share of the U.S. population who are 65+ are often exclusively described as the “small number of people exposed to high risk;” however this share is 15% of the population, or 49.5 million people. Further, there are also thousands of others at high risk regardless of age: those with underlying health conditions such as lung disease, diabetes, or heart disease. While this might sound assuring to the young and healthy, they must recognize that they may survive to spread disease to millions of vulnerable people.

Despite reports that the death rate of COVID-19 ranges from 3-4% overall, the threat to our high-risk population is much higher. One scenario by the CDC estimates as many as 200,000 to 1.7 million people in this category could die over the course of this pandemic. Suddenly, the “small number” of people at high risk no longer sounds so small.

Sourced via ProPublica

https://www.propublica.org/article/this-coronavirus-is-unlike-anything-in-our-lifetime-and-we-have-to-stop-comparing-it-to-the-flu

Preventative measures such as school closures, telecommuting, and canceling large events may sound extreme, but this is the only way to slow progression of COVID-19. Many of our lives are being upended. The profound human and economic impacts of these preventative measures cannot be dismissed. However, if we do not act aggressively, the cost will be thousands, if not millions, more lives lost and an overloaded healthcare system.

Levels of Prevention

There are three levels of disease prevention which correspond to three increasing stages of disease progression. Primary prevention strategies aim to reduce cases at the stage of susceptibility. These include educational campaigns (e.g., proper hygiene). The second level requires testing of suspected cases and isolation measures for infected persons. Because the U.S. government failed to implement widespread testing early after the first COVID-19 cases were reported in the U.S., public health officials have one remaining, third option: reduce spread by social distancing. The goal of social distancing is reduce the severity of disease spread by limiting interactions among those not yet exposed and those with asymptomatic and mild cases.

Levels of Prevention and Corresponding Stages of Disease (adapted from William Oleckno’s Essential Epidemiology)

As more mild and asymptomatic cases unknowingly spread COVID-19, there will be an increase in cases among high-risk groups. As the high-risk groups enter the “stage of diminished capacity,” there will be a rapidly increasing demand on the healthcare system to reduce complications from the disease (e.g., ventilation support).

Take Action

If your local community is not currently putting into place preventative social distancing measures, demand they do so immediately.

For those who are called upon to exercise social distancing or quarantine: please do so, because you are saving the lives of our most vulnerable.