{
  "abstract": "Background The 2022–2023 mpox outbreak in Europe was characterized by a distinct clinical phenotype, predominantly affecting gay and bisexual men who have sex with men (GBMSM) and generally presenting with mild-to-moderate disease. After a decline in incidence, despite increasing population immunity due to vaccination policies, a resurgence occurred in 2025-2026. Whether the clinical presentation and disease course changed over time remains unclear. Here we describe and compare epidemiological and clinical features of mpox cases diagnosed at a single Italian referral centre across epidemic phases.Methods We conducted a single-centre retrospective analysis (May 2022–January 2026), comparing the 2022–2023 and 2025–2026 periods. Interepidemic cases were not included. Clinical and epidemiological characteristics were compared using logistic regression models. Adjusted models included age, HIV status, CD4 T-cell count at mpox diagnosis, and any smallpox vaccination (2nd or 3rd generation).Adjusted Odds ratios (aORs) with 95% confidence intervals (CI) were estimated by maximum likelihood and represented as forest plots. Hospitalisation was defined as admission due to clinical need, not for isolation purposes. Disease severity was defined as the presence of ≥1 of the following: ocular involvement, pharyngitis, proctitis, hospitalisation, and>20 lesions.Results Overall, 162 cases were recorded (136 in the 2022-2023 vs 26 in the 2025-2026). Median age was 40 years (IQR 33–46) and all cases were male at birth; 92.0% identified as GBMSM and 45.1% were people with HIV (97.2% on ART; median CD4 644 cells/mmc [IQR 457–843]). Any smallpox/mpox vaccination was reported in 11.7%. MPXV clade Ib was detected only in 2025–2026 (23.1%) ( table 1).In multivariable logistic regression adjusted for age, HIV status, CD4 count at diagnosis and vaccination, the 2025–2026 phase was associated with markedly lower odds of hospitalization due to clinical need (aOR 0.08, 95% CI 0.01–0.64; p=0.017) and concurrent STIs (aOR 0.21, 95% CI 0.06–0.81; p=0.023).No evidence for a difference in disease severity was observed. Disease duration ≥28 days showed a non-significant trend toward higher odds in 2025–2026 with wide confidence intervals (aOR 2.13, 95% CI 0.49–9.22; p=0.313) (figure 1).Conclusions In this single-centre cohort, the 2025–2026 resurgence was associated with substantially fewer hospitalisations and lower risk of concurrent STIs, independent of measured potential confounders. Overall disease severity did not differ between phases and estimates for other outcomes - including disease duration - were imprecise due to the limited sample size. Larger, multicentre studies integrating immunological and virological data are needed to clarify the determinants of this evolving epidemic pattern.Abstract OC34 Table 1Baseline characteristics of MPOX cases, overall and stratified by epidemic wavesAbstract OC34 Figure 1Adjusted associations between epidemic phase and clinical characteristics",
  "authors": [
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "RJ Steiner"
    },
    {
      "affiliations": [
        "Institute for Applied Mathematics Mauro Picone, National Research Council, Rome, Italy"
      ],
      "name": "P Stolfi"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "V Barchi"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "G Frate"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "D Farinacci"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "R Esvan"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "L Bordi"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "G Micheli"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "A Giacinta"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "R Schiavone"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "N Braccialarghe"
    },
    {
      "affiliations": [
        "SERESMI, National Institute for Infectious Diseases Lazzaro Spallanzani IRCCS, Rome, Italy"
      ],
      "name": "G De Carli"
    },
    {
      "affiliations": [
        "SERESMI, National Institute for Infectious Diseases Lazzaro Spallanzani IRCCS, Rome, Italy"
      ],
      "name": "F Vairo"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "F Maggi"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy",
        "Health Direction, National Institute for Infectious Diseases Lazzaro Spallanzani IRCCS, Rome, Italy"
      ],
      "name": "A Antinori"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases, Lazzaro Spallanzani IRCCS, Rome, Italy, Regional AIDS Reference Center, Rome, Italy"
      ],
      "name": "V Mazzotta"
    }
  ],
  "title": "OC34 Changes in MPOX clinical presentation across epidemic phases: a single-centre cohort study in Italy, 2022-2026",
  "uid": "ad51e019-346f-5d4a-b752-a59622d3cdc6"
}