A fifth person has been confirmed as contracting hepatitis A from Fruzio Mixed Berry product.

Fruzio 1kg bags of strawberries, blackberries and mixed berries, and 500g mixed berry bags, were recalled in December after four cases of hepatitis A were linked to the products. Nelson company FSL imported the infected berries from China's Shandong province.

Photo: Fairfax.

FSL Foods recalled its berries on December 3. A day later the company voluntarily expanded its recall to include another mixed berry product, along with its frozen strawberries and blackberries.

On Monday, the Ministry for Primary Industries said a fifth person, who contracted hepatitis A from the berries had the same strain of the virus as four others who fell sick in late October and early November.

MPI plants food and environment director Peter Thomson says its investigation was ongoing and, although it was now less likely, further recalls were possible.

Anyone concerned about eating frozen berries should briefly boil them before eating or ensure cooking exceeds 85 degrees Celsius for one minute.

"Elderly persons and those with chronic liver damage should avoid imported frozen berries that have not been heat treated," Peter says.

Hepatitis can take a long time to present, between 15 and 50 days. Early symptoms can be mistaken for flu and in some cases, especially children, there may be no symptoms.

Symptoms can include: fever, jaundice, poor appetite, nausea, vomiting, stomach pain, dark urine and fatigue.