Commentary: Why it is so important to ‘flatten the curve’ on COVID-19.

By Jennifer Horney, PhD, MPH and Katie Kirsch, MS

Since John Snow, a British anesthesiologist, identified the existence and cause of an outbreak of cholera in London in September of 1854, epidemiologists have used the tools he developed in tandem with modern approaches and technologies to investigate outbreaks.

Today, calls to “flatten the curve” for the ongoing outbreak of a novel coronavirus disease 2019 (COVID-19) require public health officials, with the active support of the public, to leverage all available epidemiologic tools to understand the disease mechanisms of SARS-CoV-2, the virus that causes COVID-19, to identify factors affecting infection risk and disease severity, and to inform strategies and interventions to limit transmission and  the potential for our healthcare systems to become overwhelmed with cases of COVID-19.

Jennifer Horney

Usually public health and health care officials have multiple tools at their disposal, all that contribute towards flattening the curve – that is, reducing the number of new cases while at the same time, spreading these new cases out over a longer time period. However, there are several critical challenges to surmount in the response to COVID-19.

At this time, there are no treatments available to prevent infection, to reduce to duration of the illness or to reduce symptom severity.

We do not yet understand what role this may be playing in the reproductive rate of the virus, that is, the number of secondary cases that will become sick due to contact with one primary case.

Disease surveillance is an essential component of epidemiologic investigations; however, detection of infected cases is impeded by the time required to build nationwide diagnostic testing capacity for a novel pathogen.

 In addition, existing evidence suggests that individuals who become infected may be contagious before developing symptoms of COVID-19 and some may be asymptomatic carriers of the virus, meaning that they are capable of transmitting the disease without experiencing symptoms.

Widespread vaccination coverage and the immunity of those who have already been infected with a viral pathogen can help us reach the point of “herd immunity,” a public health concept that means that once a sufficient proportion of the population is immune to a disease through vaccination or prior infection, the risk of person-to-person transmission in community settings becomes less likely.

However, since COVID-19 is caused by a novel virus, we do not yet have antiviral medications or vaccines that have been validated and approved to provide a level of protection from infection.

Similarly, we also likely have no natural immunity, which may mean that all people are susceptible to infection. The novel coronavirus that causes COVID-19 possesses traits that enable it to evade the human body’s immune response, and the risk of reinfection among those whose bodies have previously mounted an immune response to this coronavirus has not yet been determined.

Due to the current lack of pharmaceutical interventions, such as medicines and vaccines, public health officials must rely on traditional approaches to slow the spread of COVID-19.

Katie Kirsch

The effectiveness of such measures in flattening the curve of an outbreak is reliant upon the cooperation, compliance, and support of the general public. Given that SARS-CoV-2 may survive for several days on surfaces, enhanced cleaning coupled with the appropriate application of a disinfectant that is effective against this pathogen is a critical step in reducing the risk of transmission.

Available approaches include individual actions like practicing good hand washing, respiratory hygiene and cough etiquette, as well as staying home when you are sick.

Also involved are community-level actions like the isolation of sick individuals, quarantine of their close contacts, and general social distancing of all members of the community, including those who appear to be healthy.

Social distancing may be accomplished through the cancellation of large gatherings, school and business closures, and limitations on the interactions of people without symptoms. Social distancing may be particularly important in the case of COVID-19, as early estimates show that 86% of all infections have been undocumented.

For now, as access to testing remains limited, it is very important for every individual to prioritize the safety of the entire population over their own inconvenience or disappointment due to the implementation of social distancing.

In time, all those milestone events will be rescheduled. The actions we take today in Delaware will ensure that all of us – including the elderly and the most vulnerable – will be there to enjoy them.

Jennifer Horney is professor and founding director of the epidemiology program at the University of Delaware. Katie Kirsch is a doctoral student working with Dr. Horney.