A fourth case of listeria has been confirmed in Tauranga.

Medical Officer of Health for Toi Te Ora Public Health, Dr Phil Shoemack says the fourth case was confirmed last week.

This follows on from three confirmed cases last month. Sadly, one of the people with the disease died, prompting a warning from medical professionals.

All three of those who were affected last month were between 70 and 90 years old.

The person who died already had a terminal condition, Medical Officer of Health Neil de Wet said at the time.

He said it was possible that the cases were linked, as it's unusual to see three cases in two weeks.

Following confirmation of a fourth case last week, Dr Phil Shoemack says they are continuing to work with MPI to locate a common source of each case.

'As yet, we have not managed to confirm whether there is a common source, such as a particular food.”

He says the latest case did require hospitalisation, and the person has now been discharged.

MPI compliance director Gary Orr says they are looking to see if there is a common food connection.

"Any case of listeria is a worry for us, particularly if there is a link to food ... If it is shown to have a link to food then we will move very quickly to take that risk food out of the system or alert the public."