A rise in temperature and sunny weather are forecast for this weekend, raising expectations for one last spring trip out of the city. Health authorities, however, warned Thursday of the growing risk of harmful bacteria, particularly for those who plan to go to the seaside.

The Korea Centers for Disease Control said vibrio vulnificus, a type of bacteria that causes necrotizing fasciitis, or flesh-eating bacteria syndrome, was detected in sea water collected from the country’s southern sea.

Vibrio vulnificus is found in seawater environments during the summer months. The bacteria and subsequent illness has been known to be fatal, and can be contracted through eating raw shellfish, such as oysters, contaminated with the bacteria or through exposing open wounds to sea water.

Healthy people, if infected with the bacterium, will exhibit vomiting accompanied by diarrhea and abdominal pain. The symptoms appear 20-48 hours after being infected, experts said. It can infect the bloodstream and cause skin blistering within 36 hours, which then leads to skin necrosis. The infection has a fatality rate of between 40 and 50 percent. The fatality rate is much higher for patients with chronic liver disease or diabetes.

Over the last four years, a total of 215 people were infected with the fatal bacterium in Korea, according to the KCDC. The first case of vibrio vulnificus infection is usually reported in early summer ― late May and June ― when the ocean temperature reaches a point higher than 21 degrees Celsius. The number of infection cases normally peaks in August and September, officials said.

“The best way to prevent vibrio vulnificus is to avoid raw seafood or eat cooked food,” an official at the state-run disease control center.

“If you have open wounds, you should avoid exposing the body to sea water,” he said.

Authorities are also stepping up efforts to promote public awareness of food poisoning caused by other common types of bacteria such as salmonella, staphylococcus aureus and vibrio parahaemolyticus.

People should be aware of the food poisoning risk at this particular time ― May and early June ― as many enjoy outdoor activities as the temperature rises rapidly and thus accelerates bacteria growth, an official at the Ministry of Food and Drug Safety.

An average of 6,773 food poisoning cases were reported between 2008 and 2012. Food poisoning cases reported in May and June accounted for 27 percent of the total or 1,832 people, the ministry said in its report.

Food poisoning usually causes vomiting, diarrhea and abdominal pain within 72 hours. Children, elderly people and patients with a chronic disease are much more vulnerable to food poisoning because their immune systems are much weaker than healthy people. Those suffering from similar symptoms should drink as much warm water as possible to prevent dehydration and visit a nearby hospital immediately, the ministry said.

Here are some tips to prevent food poisoning.

1. Wash your hands, utensils and food surfaces often, using hot, soapy water.

2. Cook food to a safe temperature and take processed food if possible.

3. Separate raw and cooked food to prevent cross-contamination.

4. Do not leave food that must be refrigerated or frozen for more than 10 minutes at room temperature.

5. Throw it away if you have doubts about food. If it is contaminated with bacteria, the food will contain bacteria or toxins even if it is put in the refrigerator.

By Cho Chung-un (christory@heraldcorp.com)