Risk of lymphoid malignancies increased after Puumala virus infection in Finland, 2009-2019: A retrospective register-based cohort study.

OBJECTIVES

The Puumala virus (PUUV) is a hantavirus that causes hemorrhagic fever with renal syndrome. Studies showing an increased risk of lymphoid malignancies after hantavirus infection, together with the observation that PUUV infects B cells, motivated us to study the risk of lymphoid malignancies after PUUV infection.

METHODS

We linked data from the Finnish Cancer Registry and National Infectious Diseases Register for 2009-2019. We used a time-dependent Cox regression model to evaluate the hazard of the lymphoid malignancies grouped according to the HAEMACARE classification.

RESULTS

We identified 68 cases of lymphoid malignancies after PUUV infection among 16,075 PUUV-infected individuals during 61,114,826 person-years of observation. A total of 10 cases occurred within 3-<12 months and 38 within 1-<5 years after PUUV infection, and the risk of lymphoid malignancies increased with hazard ratios (HRs) of 2.0 (95% confidence interval [CI], 1.1-3.7) and 1.6 (95% CI, 1.2-2.3), respectively. The group of mature B cell neoplasms showed an increased risk 3-<12 months and 1-<5 years after PUUV infection, HR 2.2 (95% CI, 1.2-4.3) and HR 1.8 (95% CI, 1.3-2.5), respectively.

CONCLUSION

PUUV infection is associated with lymphoid malignancies in the Finnish population, supporting the earlier studies. Further research is required to understand the pathophysiological mechanisms behind this association.