Last month, Alissa and Greg Melton were the College Station, Texas, parents of three healthy boys and had another on the way.

Then, three weeks ago, their two youngest – a toddler and preschooler – got perilously ill with a fierce strain of E. coli that landed both boys in intensive care with acute kidney failure.

Jack, 4, and 18-month-old Noah remain in fair condition at Texas Children’s Hospital while officials in their home county of Brazos try to determine how the brothers acquired the bacteria.

By Monday, the reported number of potential cases had risen from eight last week to 10. The two additional illnesses, also in the College Station area, were identified over the weekend.

The current figure includes five confirmed and five suspected cases. All but the Melton boys are adults who recovered without “significant” medical intervention, said Dr. Eric Wilke, the health authority for Brazos County Health Department.He said the agency along with state health department officials are “making good progress” in identifying the source of the bacteria. Public health authorities believe all of the infections occurred during a week in mid-April. Most adults experienced diarrhea and vomiting.