- In March 2009, a novel A/H1N1 influenza virus began its inexorable spread around the world. Information regarding disease characteristics, groups at risk and prognosis remain partial. The Epidemiology Division of the Israeli Ministry of Health performs ongoing influenza surveillance and tracking of patients in Israel. The authors set out to characterize the disease and its spread in Israel. Surveillance and investigation procedures were modified in accordance with changing Ministry of Health policy. From the outset of the outbreak and until June 30, 2009, all suspected cases of influenza A/H1N1 were investigated and laboratory verified. Starting July 1, 2009, lab confirmation was reserved for severely ill patients or those at high risk of complications. All hospitalized cases were monitored and tracked daily. By June 30, 2009, 596 patients had laboratory confirmed Influenza A/H1N1: 58% of these were aged 10-30 years, and only 5% were above 50 years of age; 58% were male. In addition to fever (83%), patients reported cough (74%), rhinorrhea (59%), and headache and sore throat (53% each). Thirty three patients were considered at high risk for complications, four of which required hospitalization in an intensive care unit; 64% of infections were acquired in Israel and 22% in the United States. By July 29, 2009, 952 additional cases had been verified. Overall, 13 of the cases had been hospitalized in intensive care, 3 of whom died. Early data indicate spread particularly to younger populations, expressing non-specific respiratory symptoms. Ongoing investment in real-time data collection and analysis will enable epidemiologists to supply the information necessary to deal with the influenza epidemic.