Results
Case Series
Our laboratory tested 17,784 samples (from 13,257 patients) for SARS-CoV-2 via rtPCR from March 18th, 2020 to October 31st, 2020. Of those, 1,566 samples (from 981 patients) were positive. Within this cohort, we found 11 patients that had at least two positive SARS-CoV-2 rtPCR tests that spanned >70 days.
Clinical Presentation
Of these 11 individuals, 6 were female with an average age of 49 years (Table 1). The majority of individuals (8 of 11) had at least 1 co-morbid condition. All patients were symptomatic prior to and at their first positive rtPCR test. Symptom durations (when available) ranged from 4-28 days. Overall, symptoms were mild and none were hospitalized. Only 1 individual presented to the ED for shortness of breath. The majority of rtPCR testing performed after 70 days was performed either as clearance for a procedure or as part of a surveillance program.
Only two individuals were symptomatic at the time of their testing >70 days after initial symptoms with their primary SARS-CoV-2 infection. Both individuals had complete resolution of symptoms with their primary infection.
Probable Re-Infection Definition
We used three criteria to assess the likelihood of a SARS-CoV-2 re-infection that occurred greater than 70 days after primary infection (described above). We found that 7 of the 11 individuals met at least one criterion for probable re-infection and all 7 of these individuals met Criteria 1 (see Figure 1 and Table 1). Three (patients 1-3) of the 7 individuals with probable re-infection had at least one negative test prior to another SARS-CoV-2 rtPCR positive test, thus fitting Criteria 2 or 3. Viral sequencing was performed, however, none of the samples >70 days out had sufficient genomic material for whole genome sequencing (WGS) or Sanger sequencing (data not shown). Four (patients 8-11) individuals did not meet any of the criteria for re-infection and were considered to be experiencing prolonged shedding of SARS-CoV-2 RNA.
Serology
Six of the 11 individuals had IgG serology testing for SARS-CoV-2 (Table 1). Only two individuals (patients 1 and 3) had a paired sample whose sera was collected before and after their probable re-infection. Neither of these individuals mounted an increase in IgG anti-S antibody levels after their probable re-infection (Table 1).