Vibrio vulnificus (Vv) can result in severe disease. Although pre-existing liver disease is a recognized risk factor for serious infection, the relative importance of other comorbidities has not been fully assessed. We analysed reports of Vv infections submitted to CDC from January 1988 to September 2006 in order to assess the role of pre-existing conditions contributing to severe outcomes. A total of 1212 patients with Vv infection were reported. Only patients with liver disease [adjusted odds ratio (aOR) 5.1)] were more likely to become septic when exposure was due to contaminated food. Patients with liver disease (aOR 4.1), a haematological disease (aOR 3.2), or malignancy (aOR 3.2) were more likely to become septic when infection was acquired via a non-foodborne exposure. As such, patients with these pre-existing medical conditions should be advised of the risk of life-threatening illness after eating undercooked contaminated seafood or exposing broken skin to warm seawater.