Reactive lymphocytes in patients with Covid‐19

Abstract

From January 23 to February 27, 2020, Singapore had 96 Covid‐19 cases confirmed by real time reverse transcriptase‐polymerase chain reaction (RT‐PCR) for SARS‐CoV‐2. We examined the peripheral blood films of 32 patients and found reactive lymphocytes as shown in the top images in 23 cases (72%). This is in stark contrast to the coronavirus responsible for the 2003 SARS outbreak where reactive lymphocytes of this type were not present in a review of 185 SARS cases in Singapore and were present in only 15.2% of 138 cases in Hong Kong (Chng et al., 2005; Lee et al. 2003).