The CDC has also confirmed that a further 133 people have been infected with any of the four outbreak-associated strains across 26 US states.
In addition to the CDC’s 28 reported deaths, one pregnant woman had a miscarriage as an effect of the infection.
The outbreak – which has been attributed to listeria-infected Jensen Farms cantaloupes – is the worst US foodborne outbreak in more than a decade.
The US Food and Drugs Administration (FDA) officials last week released the results of an investigation into the outbreak, which they were able to attribute to packaging machinery at a Jensen Farms plant.
The CDC has warned that more Listeria cases related to Jensen Farms cantaloupes may still be reported, as listeriosis can develop up to two months after consumption of contaminated food.