Epidemiological aspect of COVID-19 testing

Some excerpts from the news

US Food and Drug Administration (FDA) commissioner Stephen Hahn, MD, is self-quarantining after coming into contact with a person who tested positive for SARS-CoV-2, Reuters reports. Hahn took a diagnostic test and got a negative result. In related news, Katie Miller, press secretary to Vice President Mike Pence, tested positive for SARS-CoV-2 on Friday (5/8/20). Why “in related news”? Why is it the news?

On Saturday, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, and Dr. Robert Redfield, director of the Centers for Disease Control and Prevention, said they will quarantine for 14 days. Both captains on the helm of the epidemic medical management’s ship are in quarantine. The third, Dr. Deborah Birx, the White House Coronavirus Task Force response administrator, challenged the CDC Director “There is nothing from the CDC that I can trust!” Alex M. Azar, the Secretary of Health and Human Services, is not in the news at all. Is the COVID-19 epidemic task force tested three times per day?

Some reminiscences

Reminiscences of my prior experience in epidemiologic practice might influence some bias to current approaches in COVID-19 epidemic.

My first job after medical school, as a doctor, was an epidemiologist position back in Russia, in Karelia near the Finland border in late 1960s. A rural place with scattered collective dairy and fur farms, lumber forest harvest factories surrounded by abounded GULAG camps. Periodic local epidemics were casual as fact of life. Dysentery, hepatitis A among people, sporadic anthrax, tularemia, foot-and -mouth disease among animals. Every epidemic had been managed from the start according infectious epidemiology rules: isolation, testing, hospitalization, local quarantine, disinfection, sanitary. In some occasions, the efforts to decrease the epidemic failed despite all standard efforts. One of the suspected culprits was the continuation of testing. When the testing was limited only to clinical necessity, the epidemic abruptly subsided. Until today, I do not have a rational explanation. Hypothetical thoughts are still lingering.

Some excerpts from basic epidemiology

Common sense and humans experience determine one of the main infectious epidemiology rules as the detection of infected to isolate from the population, as a rotten apple. Testing is an apparent solution. This post is intended to explore the testing notion as epidemiology tool to overcome the spread of COVID-19 epidemic in the USA.

Testing of patients, which require hospitalization or other clinical actions, is an apparent necessity for the differential diagnosis and effective treatment. The rest of testing is the epidemiology work routine. The diagram below presents main directions of this work. Testing with a clear plan of actions, which is following positive or negative result, is only are part of them.

The importance of each component is different depending on infection, local conditions, morbidity, mortality etc. etc.  In the case of COVID-19 epidemic, immediate contact testing prevails institutional contacts, while screening testing within a particular facility is incomparably more significant than the exposure testing to individuals. The latter issue requires special detailed discussion, a special post.

Testing priorities

Below is the excerpt from PRIORITIES FOR COVID-19 TESTING section Evaluating and Testing Persons for Coronavirus Disease 2019 (COVID-19) by Center Disease Control and Prevention (CDC). Revisions were made on May 3, 2020

The entire document is pointing in the wrong direction from the epidemiology perspective.  The serious objection would be on the division for High priority and Priority. The division itself and the content of the document reflect, in my view, misunderstanding by CDC strategic goals of actions in the current epidemic.

Practical epidemiology perspective

Below are my considerations regarding priorities in testing based on my prior experience as a practical infectious epidemiologist.

Hospitalized patients with symptoms are already isolated in the hospital. Their test should be done for the differential diagnosis followed by appropriate treatment.

Healthcare facility workers, workers in congregate living settings, and first responders with symptoms are already ill. Their testing is not a priority, but isolation them from contacts during their professional duties would be a priority with following testing just for clinical handling them as patients.

Residents in long-term care facilities or other congregate living settings, including prisons and shelters, with symptoms are really a high priority for separation them from the rest although this epidemiologic action would be right to do immediately even without a testing.

The testing of contacts is the necessity for localization of the source of infection. Although in a case of COVUD-19 epidemic this is a difficult task as usually in an airborne infection, an attempt would be justifiable.

“Persons without symptoms who are prioritized by health departments or clinicians, for any reason, including but not limited to: public health monitoring, sentinel surveillance, or screening of other asymptomatic individuals according to state and local plans.” These groups are a real priority for testing from the epidemiological approach, although they are in the end of the list of priorities. The main problem is that there are not local plans for such prioritizing, at least they are not in the public domain. For example, from Michigan Department of Health and Human Services

This document adds critical infrastructure workers category. The rationale is to diagnose in time infected and take them out for quarantine. When? How often? How? Etc.  This document is in line with Michigan medical officials’ uninformative briefings.

Summary of epidemiological aspect of COVID-19 testing 

First. Separation of the clinical and epidemiologic lines of testing should be clearly formulated in plans and actions.

Second. From the epidemiology perspective, the indication for testing of contacts includes two main groups: immediate contact with a clinically ill person and determination of individuals for testing in a contacts group.  Aggressive and fast testing of infected and especially contacts in congregated living, public, and work settings is effective in the beginning of the epidemic. Screening is important in the case when the source of infection’s spread is unknown. However, screening brings mixed results when the epidemic is to some degree contained.  

Third. The number of tests, as evidence of success in curtailing the epidemic, inevitably leads to relaxation of specimen’s collection, transportation, and the tests’ quality. The latter is accepted by the society as the Sun’s rise on the East. This issue will be discussed in a separate post.

I do not have an illusion that this post will change the course of actions during the current epidemic. Hopefully, my remarks regarding testing during an epidemic might be useful.

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One Response to Epidemiological aspect of COVID-19 testing

  1. Clifford Chapman says:

    Dr. Dimenstein, You have performed an invaluable service by providing scientific based information, based on your personal epidemiological, in a clear and concise manner – without the current widespread politicization of information coming from the CDC and other government representatives and organizations. Thank you.

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