A pregnant woman has died of the foodborne illness listeriosis, the Gauteng Department of Health said on Monday.
The woman died at the Steve Biko Academic Hospital on Friday, after she was admitted for listeriosis, said spokesperson Lesemang Matuka.
Matuka said he was awaiting a report from the infection control experts for more details.
The disease has already claimed more than 30 lives.
Last Thursday, the City of Johannesburg said it had activated outbreak response teams across the city to "help educate the public" on preventing the spread of listeriosis.
Health and Social Development MMC Mpho Phalatse called on residents to educate themselves on the types of food that are most likely to contain listeria, and what preventative measures to take.
She said that pregnant women and the elderly with compromised immunity were particularly at risk.
About 36 people have succumbed to the disease, which can be treated with antibiotics.
The bacteria is found in soil, water and vegetation. Of the 557 cases reported, the majority have come from Gauteng.
Of the 345 cases reported in Gauteng, 172 were reported from the City of Johannesburg.
Listeriosis is a foodborne illness that is associated with eating a wide variety of food contaminated with listeria monocytogenes, including dairy products and produce, fresh vegetables and fruit, as well as ready-to-eat products.
After infection, the incubation period varies and can be between three to 70 days.