Scientists have estimated how quickly certain E. coli strains spread between people and found one lineage with a basic reproduction number comparable to H1N1 swine flu. Drawing on genomic data from the UK and Norway, the analysis—published November 4, 2025, in Nature Communications—models transmission for three ST131 clades and underscores implications for tracking antibiotic-resistant infections.
New research reports that a human‑associated E. coli clone can spread between people at a pace comparable to the 2009 H1N1 swine flu, based on first‑of‑its‑kind estimates of the basic reproduction number (R0) for gut‑colonizing bacteria. The study, published November 4, 2025, focuses on three clades of the globally distributed ST131 lineage: ST131‑A, ST131‑C1, and ST131‑C2. (dx.doi.org)
Quantitatively, the authors estimate R0 values of 1.47 for ST131‑A, 1.18 for ST131‑C1, and 1.13 for ST131‑C2—indicating markedly higher transmission potential for ST131‑A. (dx.doi.org)
To infer these values, the team combined colonization data from the UK Baby Biome Study with genomic surveillance of E. coli bloodstream infections in the UK and Norway. All sequencing was carried out at the Wellcome Sanger Institute, and the model was built using ELFI (Engine for Likelihood‑Free Inference). (sanger.ac.uk)
E. coli typically resides harmlessly in the gut and is not transmitted via airborne droplets; spread can occur through close contact (for example, kissing) or indirectly through shared surfaces, food, or households. (sciencedaily.com)
The study finds that ST131‑A spreads as rapidly as viruses behind major outbreaks, including H1N1. By contrast, ST131‑C1 and ST131‑C2 spread more slowly among healthy people but are likely to transmit faster in hospitals and other healthcare settings. These two clades are resistant to multiple antibiotic classes and rank among the most common causes of urinary tract and bloodstream infections in the UK, and are among the most common in Norway. (sanger.ac.uk)
Adding context on resistance burdens, UK Health Security Agency data show that in England in 2021 more than two‑fifths of E. coli bloodstream infections were resistant to co‑amoxiclav, a key hospital antibiotic. (gov.uk)
“This was a first for any bacteria that live in our gut microbiome,” said co‑first author Fanni Ojala of Aalto University, referring to estimating an R0 for gut‑colonizing bacteria. (sanger.ac.uk)
“Having the R0 for E. coli allows us to compare spread across infections,” added senior author Jukka Corander of the Wellcome Sanger Institute and the University of Oslo, noting the need to probe genetic drivers of transmission. (sciencedaily.com)
The authors say the framework could guide targeted monitoring to prevent outbreaks and help reduce reliance on broad‑spectrum antibiotics. They add that the approach could be adapted to other bacterial pathogens. (sanger.ac.uk)