Norwegian health authorities are warning people who are particularly vulnerable to Vibrio infections to take precautions while swimming as a number of serious bacterial infections have been recorded.

Vibrio vulnificus/CDC
Vibrio vulnificus/CDC

This summer, six people have been severely ill with wound infection due to bacteria in seawater (five Vibrio and one Shewanella). The infection has occurred after swimming in the Oslo Fjord.

All adults over the age of 50 who have had a sore wound or have suffered sores during bathing in the Oslo Fjord in five different municipalities, Bærum, Oslo, Moss, Vestby and Fredrikstad.

In addition to the serious cases we know from earlier, there have been reports of 20 people who have had mild Vibrio infections on August 8th. These are sore infections and ear infections that often do not require treatment.

“It is not unexpected to find cases of mild vibrio infections considering how many have bathed and with the high temperatures we have had in summer. These findings do not change the advice we have already given that will apply to this year’s bathing season, “says Senior Advisor Line Angeloff at the Department for Food, Water and Animal Infection at the National Institute of Public Health.

“Swimming generally is healthy and gives you pleasure in the warm days we have had this year. We do not want to take bathing pleasure from people, but it is important that those who are particularly vulnerable take their precautions”.

Due to the prolonged warm weather in many places, the water temperatures for a long period have been higher than usual. High water temperature provides better growth conditions for some bacteria found in brackish and salt water. High water temperatures in the Oslo fjord and along the coast of Telemark and Sørlandet can lead to increased bacterial growth. Some of these, such as  Vibrio vulnificus, Vibrio parahaemolyticus and Shewanella putrefaciens, can cause serious infections in people who swim in coastal areas with high water temperatures. It is unclear when the bacteria will disappear from the coastal areas of southern Norway.

Infection can occur when bathing through wounds (including recent tattoos). Persons with proven immunodeficiency, elderly persons or people with liver disease or hemochromatosis  are particularly vulnerable. The infection may present from a lighter ear infection, wound infection, to more severe disease such as blood poisoning.


Shewanella  is a bacterium that, like Vibrio, is found in seawater and can infect bathing at sustained high sea temperatures. The mode of infection and disease presentation are the same as Vibrio infections and infection can cause serious illness.

“Such infections are fortunately very rare, but there is reason to advise on how to prevent infection,” says Director General Line Vold at the department for infection from food, water and animals at the Norwegian Institute of Public Health.

These tips are:

  • Persons with open wounds should not swim in seawater unless the wound can be covered with solid, waterproof plastics. This is especially true of elderly people, people with liver disease and people with immunodeficiency (for example, people who use anti-immune medicines).
  • People with immunodeficiency, liver disease and the elderly are advised to wear bathing shoes to prevent wounding during bathing.
  • Rinse with clean freshwater after sea bath is recommended for all persons who have wounds or injure wounds during bathing. This is especially true for people with immunodeficiency, liver disease and the elderly.
  • The risk is reduced by just taking short baths and drying out thoroughly with a clean towel after bathing.
  • Anyone who bites with wounds or injures a wound during bathing should monitor any worsening of the wound and promptly contact a doctor / medical officer for signs of wound infection, fever or impaired general condition. Tell the doctor that you have bathed. Any infection will most likely occur within one to two days.

In addition, the Norwegian Food Safety Authority warns against eating raw oysters caught in the Oslo Fjord, as well as by the coast of Telemark and Sørlandet because of Vibrio.