Serologic Study Finds Hantavirus Exposure in Northwestern Italy

A retrospective serologic study of patients in northwestern Italy from 2004-2018 found evidence of hantavirus exposure in 7.3% of samples tested, adding to sparse data on rodent-borne viral infections in a region where they have not been extensively studied. The findings were published in Emerging Infectious Diseases.¹

Researchers tested 371 plasma samples collected from 2004 through 2018 in the Italian provinces of Novara, Biella, Vercelli, and Verbano-Cusio-Ossola, part of the Piedmont region in northwestern Italy.¹ Participants had a mean age of 59.9 years and included patients being evaluated for various chronic conditions, including nephrologic disease, alcohol use, and hepatitis C virus infection.¹ Of 371 patients, 27, or 7.3%, tested positive for hantavirus antibodies by immunofluorescence assay, and 2.7% tested positive for lymphocytic choriomeningitis virus (LCMV) antibodies, consistent with rates previously reported in the nearby Trentino region.¹²

Nearly 8% of patients tested showed serologic evidence of hantavirus exposure

Neutralization testing showed hantavirus-positive samples reacted predominantly against Puumala virus (PUUV) rather than Dobrava virus (DOBV), suggesting PUUV as the likely infecting strain in most cases, even though several samples were initially positive for DOBV IgG by immunofluorescence assay.¹ Neutralization against DOBV was largely absent or detected only at low titers, a pattern the study authors said is consistent with serologic cross-reactivity rather than true DOBV infection.¹ One sample showed reactivity to both viruses on an immunofluorescence assay and a mixed neutralization profile, which the authors said could indicate exposure to an antigenically related hantavirus or cross-reactive antibodies.¹

The 7.3% hantavirus seropositivity rate identified in this study was higher than the 0.2% DOBV IgG rate previously reported among forestry workers in Trentino and above an estimated 1.7% average for the general Italian population, though below the up to 8.8% seroprevalence reported in occupationally rodent-exposed groups elsewhere.^1,2 DOBV and PUUV both cause hemorrhagic fever with renal syndrome, while LCMV, transmitted by house mice, can cause febrile illness or aseptic meningitis.¹

Findings Highlight a Diagnostic Gap in Italy

Rodent-borne infections, including hantavirus and LCMV, are not commonly diagnosed in Italy despite existing evidence of viral circulation and human exposure in several regions.¹ The study authors said their findings support the need for greater clinical awareness and diagnostic consideration of hantavirus and LCMV infection in northwestern Italy, a region that has received comparatively little study relative to areas such as Trentino, echoing occupational risk patterns documented for hantavirus exposure elsewhere.¹

The study was conducted by researchers affiliated with Uppsala University in Sweden and institutions in Italy, using stored samples originally collected for unrelated clinical studies. Because samples were not collected for the purpose of assessing rodent-borne virus exposure specifically, the study authors noted their findings offer a starting point for more targeted surveillance rather than a definitive prevalence estimate for the broader population, a reminder that environmental disruption can also reshape rodent-borne disease risk.¹

Previous Coverage on Hantavirus From the Cruise Ship Cluster

These findings arrive months after Contagion covered an unrelated hantavirus pulmonary syndrome (HPS) cluster tied to Andes virus exposure aboard a cruise ship, which had grown to 13 confirmed and probable cases and 3 deaths as of late May.³ Gavin Harris, MD, associate medical director of the Serious Communicable Diseases Program at Emory University, told Contagion that supportive care, including early critical care measures such as ventilators and dialysis, remains the primary treatment for HPS, alongside investigational antivirals used off-label, including ribavirin, favipiravir, and baloxavir.³

David Wohl, MD, professor of medicine in the Division of Infectious Diseases at UNC, told Contagion that the limited number of additional cases following the cruise ship cluster offered some reassurance about person-to-person transmissibility of Andes virus, though he cautioned that surveillance gaps made it difficult to rule out undetected secondary transmission.⁴ Wohl said the clinical presentation of Andes virus closely resembles that of Sin Nombre virus, the hantavirus more commonly seen in North America, and that hantavirus pulmonary syndrome remains a serious, potentially fatal complication regardless of strain.⁴

References

1. Faolotto G, Wasberg A, Iheozor-Ejiofor R, Korhonen EM, Minisini R, Sironen T, et al. Serologic evidence of hantavirus exposure in humans, Italy, 2004-2018. Emerg Infect Dis. 2026;32(9). doi:10.3201/eid3209.261840

2. Kallio-Kokko H, Laakkonen J, Rizzoli A, Tagliapietra V, Cattadori I, Perkins SE, et al. Hantavirus and arenavirus antibody prevalence in rodents and humans in Trentino, northern Italy. Epidemiol Infect. 2006;134:830-6.

3. Harris GH, Parkinson J. Treating the Andes strain of the Hantavirus associated with the cruise ship cluster. ContagionLive. Published May 28, 2026. Accessed July 31, 2026. https://www.contagionlive.com/view/treating-the-andes-strain-of-the-hantavirus-associated-with-the-cruise-ship-cluster

4. Wohl D, Parkinson J. The mysterious contagiousness of the cruise ship strain of the Hantavirus. ContagionLive. Published May 22, 2026. Accessed July 31, 2026. https://www.contagionlive.com/view/the-mysterious-contagiousness-of-the-cruise-ship-strain-of-the-hantavirus