Figure S1 Neutralization assays against group 1 influenza viruses. Dose-response curve fit nonlinear regression is reported for IgG PN-SIA49 against neutralized group 1 influenza viruses. (A) Results from fluorescence inhibition assays, (B) plaque reduction assays and (C) infectious foci formation reduction assays. Data from at least two different experiments for each virus are reported. Each point was performed in triplicate. (PDF) Figure S2 Influenza hemagglutinin unrooted phylogenetic tree of all the viral strains tested in neutralization assays with PN-SIA49. Viral isolates belonging to group 1 and group 2 are divided into two different boxes. Subtypes that can be neutralized by PN-SIA49 are indicated with a green '+', while the ones that cannot be neutralized are indicate with a red '2'. As reported in the text, PN-SIA49 is able to neutralize all of the group 1 viruses tested in this study except for the H9N2 strain. No neutralizing activity was detected against the H3N2 viruses tested. * The recombinant HA from A/South Carolina/1/1918 (H1N1) pandemic strain was previously shown to be bound by PN-SIA49 [26, 27] . # H1N1 A/New Caledonia/20/1999 was previously shown to be neutralized by PN-SIA28 as Fab fragment [26, 27] . (PDF) Figure S3 C179/PN-SIA49 competition assay. Graphic representation of cell staining and flow cytometric analysis of HEK293T cells transfected with the pcDNA 3.1D/V5-His-TOPO vector containing the HA-A/PR/8/34 were performed. Serial dilutions of PN-SIA49 were used in combination with a fixed concentration (1 mg/ml) of C179 (blue line). A monoclonal antibody directed against the HA globular head was used as competition negative control (pink line). (PDF) Figure S4 HA mutants that determine a decrease of PN-SIA49 binding to HA are expressed at the same level of wild type HA on cell surface. FACS curves showing the binding of anti-H1N1 HA antibody (directed against a linear epitope) to untransfected cells, HA wild-type and HA-mutants. White and red curves represent, for each graph, respectively the binding of anti-HA expression control to untransfected cells and wild type H1N1-HA. The different colour curves represent the different mutants. (PDF)  Web-based Investigation of Multistate Salmonellosis Outbreak We investigated a large outbreak of Salmonella enterica serotype Javiana among attendees of the 2002 U.S. Transplant Games, including 1,500 organ transplant recipients. Web-based survey methods identified pre-diced tomatoes as the source of this outbreak, which highlights the utility of such investigative tools to cope with the changing epidemiology of foodborne diseases. T he epidemiology of foodborne illnesses is influenced by a variety of factors, some of which have changed dramatically in recent years. The increased availability of preprocessed foods and the improved survival of persons with immune defects have affected the sources and nature of foodborne illness (1) (2) (3) (4) . Increased mobility of Americans through interstate travel has complicated the identification and investigation of outbreaks. New technologies for outbreak investigation have the potential to greatly assist public health officials in successfully managing these changing factors. We describe an outbreak of Salmonella enterica serotype Javiana infections affecting a large group of geographically dispersed organ transplant recipients. The prompt and successful investigation of this outbreak was facilitated by the use of Web-based surveys.