Officials with the Norwegian Institute of Public Health report seeing an increase in listeriosis cases in December, prompting a warning for high-risk groups.

Image/Robert Herriman
Image/Robert Herriman

According to an official notice Friday (computer translated), six cases were reported this month when the country typically sees 1-2 cases a month.

Four of the six patients reported in December are from Hedmark and Oppland.

Health officials are working to identify if their is a common food source linked to the increase in cases.

Listeria is usually transmitted through food, especially long-life foods that are refrigerated and eaten without further heat treatment. Many of these food products are popular as Christmas foods and can be found on many Christmas parties.

People in the risk groups for listeriosis, ie pregnant women, persons with impaired immune systems and the elderly with impaired general condition, should, as usual, avoid food products that may pose a risk to listeria infection, says consultant Hans Blystad at the Norwegian Institute of Public Health.

Such food products are:

  • rakfisk
  • Products made from unpasteurized milk
  • Soft and semi-soft cheeses, such as brie, camembert, and other molds – whether or not they are made from pasteurized milk

Consumption of food contaminated with L. monocytogenes can cause listeriosis, a serious infection that primarily affects older adults, persons with weakened immune systems, and pregnant women and their newborns. Less commonly, persons outside these risk groups are affected.

Listeriosis can cause fever, muscle aches, headache, stiff neck, confusion, loss of balance and convulsions sometimes preceded by diarrhea or other gastrointestinal symptoms. An invasive infection spreads beyond the gastrointestinal tract. In pregnant women, the infection can cause miscarriages, stillbirths, premature delivery or life-threatening infection of the newborn.

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In addition, serious and sometimes fatal infections in older adults and persons with weakened immune systems. Listeriosis is treated with antibiotics. Persons in the higher-risk categories who experience flu-like symptoms within two months after eating contaminated food should seek medical care and tell the health care provider about eating the contaminated food.


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