Occult SARS-CoV-2 infection; a possible hypothesis for viral relapse.

Coronavirus disease 2019 (COVID-19) has emerged as a global public health emergency, which is characterized by high infection rate and fatal course. Recent data reported that the test for Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) RNA might become positive again after one or two consecutively negative tests. Many researchers are currently evaluating the clinical characteristics of the SARS-CoV-2 reactivation. In this letter, we proposed a possible mechanism of SARS-CoV-2 reactivation or relapse after negative nasopharyngeal swabs PCR.