MechanismsHumans889,215 participantsCohort studyDose-response

Blood stem-cell mutations linked to serious bacterial infections

In an analysis of 889,215 people, clonal blood mutations were associated with serious bacterial infections, with a hazard ratio of 1.22.

Figure 1 from Nature Communications — Figure 1Fewings et al. · CC BY-NC-ND

Nature Communications9 Oct 2026, 01:59 BST

In an observational study of 590,537 people from three population cohorts, validated across 889,215 individuals, researchers examined the health effects of clonal haematopoiesis. This condition occurs when blood stem cells acquire genetic mutations that drive clonal expansion.

The researchers identified mutations across 43 genes in 40,560 people, or 6.87% of the initial group. Clonal haematopoiesis was associated with developing a serious bacterial infection, with a hazard ratio of 1.22, and with 28-day post-infection mortality, with a relative risk of 1.84. These links remained independent of blood malignancies and inflammatory conditions. Certain mutations carried higher hazards, particularly in splicing factors: between 22% and 25% of individuals with expanded SRSF2 P95 clones developed a serious bacterial infection within 10 years.

Why it matters

Serious infections become increasingly common and severe in later life. Understanding how somatic mutations in blood stem cells alter infection risks may help clarify why some individuals experience greater susceptibility to life-threatening illnesses.

Caveats

Because the research relied on observational cohort data, it shows statistical links rather than showing that mutated blood cells cause bacterial infections. Residual confounding from unmeasured health conditions or differences across biobanks may also have affected the results.