The new outbreak-related death was in Oregon; the previous two were in Minnesota.
The outbreak, linked to precut cantaloupe, has now topped 100 illnesses in 34 states.
The US outbreak has more than doubled in just a week, has hospitalized at least 45, and has killed 2 Minnesotans.
So far at least 11 people in seven states have been sickened with Listeria monocytogenes, which can cause severe and fatal infections.
Most of the patients are babies who likely got sick after touching dog food or were exposed to dogs and their environments.
The strain is linked to travel to Mexico, consumption of cheese obtained in Mexico, and beef from Mexico and the United States.
With the exact source still murky and investigations still under way, officials expect more cases.
Interviews with sick patients and trace-back investigation pointed to a specific diced onion producer.
Sixteen of 30 case-patients were linked to wild-bird exposure, and sequencing found a similar Salmonella strain in dead songbirds.
Patients with resistant Salmonella infections had a higher risk of hospitalization, but the study authors say host and strain factors may play a role.