“An 82-year-old male with a history of advanced Parkinson’s disease, insulin-dependent diabetes, chronic kidney disease, and hypertension presented to the emergency department (ED) in early-April 2020 with one week of fever and shortness of breath. He was hemodynamically stable, but tachypneic, hypoxic to 89% on six liters of oxygen via nasal cannula, and febrile to 100.4 °F. Chest x-ray revealed peripheral and basilar patchy opacities concerning for COVID-19 (Fig. 1A). His respiratory status declined in the ED, and he was intubated for hypoxemic respiratory failure and admitted to the intensive care unit (ICU). An RT-PCR for SARS-CoV-2 sent from the ED resulted as positive. He remained intubated in the ICU for 28 days at which point he was successfully extubated and transferred to the medicine floor. He demonstrated clinical and radiographical improvement (Fig. 1B), and in early May 2020 two subsequent RT-PCRs for SARS-CoV-2 sent 24 h apart resulted as negative. On hospital day 39, he was discharged to a rehabilitation facility breathing comfortably on room air.

Ten days post-discharge (48 days after first presentation), he re-presented to the ED with fever and hypoxia. On arrival he was tachypneic, hypotensive to 70/40 mmHg, and tachycardic to 110 beats/min, with a temperature of 99.9 °F and oxygen saturations of 83% on room air which improved to 96% on eight liters via Oxymizer®. Chest x-ray (Fig. 2A) and computed tomography (CT) scan (Fig. 2B) demonstrated bilateral ground glass opacities again concerning for COVID-19, as well as unilateral focal consolidations concerning for bacterial pneumonia. RT-PCR for SARS-CoV-2 sent from the ED again resulted as positive.”

Was this reinfection? Alternate considerations include the patient shedding virus for a longer period or inaccurate testing.

Genetic material from viruses can stay in a host longer even after live virus has been cleared and after symptoms have resolved. Also, how much virus is shed can depend on how sick the patient was.

According to the article, testing can be inaccurate and imprecise, with test sensitivities of 66% to 80%, depending on what instrument is used. Some tests are sensitive to “multiple different gene targets, some of which are very specific to SARS-CoV-2 infection, and some of which are quite sensitive to detection but may be common among many or all SARS-like coronaviruses.”

However, for this case study, “For our patient, while his RT-PCR on re-presentation was in fact positive, the cycle threshold required for detection was relatively high suggesting a low viral load. This could be explained by either prolonged low-level viral shedding, or inadequacy of the submitted sample. Additionally, at the time of representation and repeat positive testing, further assessment of his results revealed that while the gene assessed which was very sensitive for infection but common among all SARS-coronaviruses was detected, the gene assessed which was specific to SARS-CoV-2 was not identified.”

In conclusion, “There is large variability between instruments used for SARS-CoV-2 RT-PCR testing, and many of these results are largely open to interpretation. As in our case, interpreting cycle thresholds and understanding more about the targets of a particular instrument used for SARS-CoV-2 RT-PCR can be crucial for clinicians assessing for the possibility of true reinfection in their patients.”

Duggan NM, Ludy SM, Shannon BC, Reisner AT, Wilcox SR. A case report of possible novel coronavirus 2019 reinfection [published online ahead of print, 2020 Jul 4]. Am J Emerg Med. 2020;S0735-6757(20)30583-0. doi:10.1016/j.ajem.2020.06.079