An on-going cluster of low-level Listeria has sickened seven people in three Texas counties this year, killing two of them.

The Express-News reports the patients — five from Bexar County and one each from Travis and Hidalgo counties — developed listeriosis.

Roger Sanchez, senior epidemiologist with the Metropolitan Health District, said genetic analysis found the identical strain of bacteria in all the patients, suggesting they were infected by the same food item. But because of the small numbers and the dispersal of cases — two of the patients lived 300 miles apart — it might be difficult to pinpoint the cause, adding,

“This is not a large outbreak. What made it bad is that it has infected people who are fragile, elderly people.”

Sanchez said the infected patients ranged from ages 66 to 93. Most had serious underlying health problems, and all but one were hospitalized either before or during their infection.

The first case was reported in January, the most recent May 6.