The Association of Human Parvovirus B19 Infection on the Course of Vietnamese Patients with Rheumatoid Arthritis.

: Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease, and progressive arthritis is its primary clinical manifestation. The role of human parvovirus B19 (B19V) infection in the progression of RA remains unclear. This study aims to investigate the association between B19V infection and viral genetic distribution in Vietnamese RA patients. : 115 Vietnamese RA patients and 86 healthy controls (HCs) were enrolled in this observational study at the Thai Nguyen National Hospital from January 2019 to December 2021. B19V DNA was examined in serum and synovial fluid samples from RA patients using nested PCR and real-time PCR. B19V antibodies were detected in serum samples using ELISA. : B19V DNA was detected in the serum of 2 out of 115 (1.74%) RA patients but not in any HCs. Interestingly, B19V DNA was present in 12 out of 68 (17.65%) RA patients with knee effusion in their synovial fluid. Anti-B19V-IgG and anti-B19V-IgM were detected in the serum of 42.61% and 2.61% of RA patients, respectively, and in 24.42% and 12.79% of HCs, respectively. Anti-B19V-IgG levels were significantly higher in the serum of RA patients than in the serum of HCs ( = 0.007). However, anti-B19V-IgM was more commonly detected in HC serum than in RA patient serum ( = 0.006). Phylogenetic analysis showed that all B19V strains belonged to genotype 1 and subgenotype 1A. : B19V infection is frequent in RA patients and suggests a contribution of B19V to the progression of RA, particularly in a B19V genotype-1- and subgenotype-1A-dependent manner and emphasises the need for early detection and management of B19V infection in RA patients.