More and more reports of individuals who suffered Covid-19 "reinfections" have been described in recent weeks. However, health officials debate the entire entity of what these reinfections exactly are. How should businesses who encounter these individuals then respond when these individuals are otherwise healthy to function in the workplace? This question has major implications since health officials had considered previous infection a stepping stone to subsequent immunity and protection from Covid-19. The notion that these individuals can become reinfected completely refutes this concept of acquired immunity.
To understand the best strategy to manage these individuals, the initial approach is to study the definitions involved in reinfection. The most common definition of "reinfection" of Covid-19 is a laboratory definition and describes an individual who tests positive for Covid-19 disease, then tests negative, and then subsequently tests positive later.
Two major groups using definition have released data on these reinfections. First, a cluster of 13 sailors from the USS Theodore Roosevelt were noted to be reinfected this weekend from their infected and recovered cohort. Additionally, a previous study from South Korea showed that 163 out of the 7829 recovered patients (2% rate) in that country had become reinfected. In the South Korean study, individuals retested positively up to 35 days after the initial infection. This latter study also described that 61 of the 163 patients had new symptoms.
A clinical definition of "reinfection" was not used in these reports to describe the initial infection or the second infection. That signifies that the presence, resolution, and recurrence of symptoms were not included in the definition of reinfection in these studies. The studies used PCR tests which detects the presence of viral particles by polymerase chain reaction from nasopharyngeal swabs. Importantly, neither of these two reports discussed whether any standardization of the testing protocols existed and whether any of the tests were based on clinical suspicion or some other surveillance protocol.
Several potentially plausible scenarios might explain these results. In scenario 1, individuals actually have the disease, are cured, and then develop a new disease. In scenario 2, the virus is never fully eliminated and the second test is considered a false negative test. This scenario could be also a "reactivation" in that the viral particles are of such a low level that they do not make the testing threshold to detect the viral particles. The viral particles may then have multiplied enough to make the test recognize them or have the patient become symptomatic. In scenario 3, the disease is not recurring viral infection but the persistent detection of shed viral particles.
Businesses should understand each of these potential scenarios and their implications. They should understand that past infection does not eliminate the risk of that individual being reinfected or infecting others even though the likelihood is small. Additionally, the employers may want to consider a plan for these scenarios when they plan their testing strategy. They may consider keeping those with past infections to be a part of surveillance testing in the future along with those individuals who were never infected. Finally, businesses should be monitoring the quality of their tests and the possible chances of false-positives and false-negatives to they can understand what these tests could mean for their workforces.