Before closing their investigation into a multistate outbreak of E. coli O145, health officials identified 3 more victims – bringing the case count up from 15 to 18 – but were unable to find the source of the bacteria. The outbreak, largely concentrated in the southeastern United States, started in mid-April. The last reported illness began June 12. Out of the 18 victims in 9 states, 4 were hospitalized. A 21-month-old girl from Louisiana died from her infection. Victims ranged in age from 1 to 79, with a median age of 33. Infections predominantly affected women, who constituted 73 percent of the victims, according to the final outbreak report from the Centers for Disease Control and Prevention, published Friday. The total case count by state is as follows: Alabama (2), California (1), Florida (1), Georgia (5), Kentucky (1), Louisiana (5), Maryland (1), Tennessee (1), and Virginia (1). The 3 new illnesses identified since CDC’s last update on June 22 occurred in 3 states: Kentucky (1), Maryland (1) and Virginia (1). CDC and public health officials interviewed 15 of the infected individuals to see whether a they had had common food exposures in the week preceding their illnesses, but no source was identified. E. coli O145 is one of what scientists have deemed the “Big Six” E. coli strains – the six most common virulent strains of E. coli after E. coli O147:H7. Together, the Big Six cause an estimated 113,00 illnesses in the U.S. each year, according to the CDC. In April of 2010, an outbreak of E. coli O145 linked to romaine lettuce sickened 33 people; 13 were hospitalized. Later that year another E. coli O145 outbreak linked to smoked meats affected at least 7 people. This year’s mystery outbreak was the first known to be linked to the bacteria since that time.