The Department of Health has announced the fourth case of cholera in Taiwan, a middle-aged man who had profuse watery diarrhea after he consumed raw fish. Doctors say that people with weak immune system or chronic diseases face higher risks of infection and are suggested not to eat uncooked seafood.

The 56-year-old man living in Taipei displayed symptoms of serious watery diarrhea after he consumed raw fish in a Japanese restaurant and was later confirmed to be the fourth officially-reported cholera case in Taiwan.

After examining the restaurant's food samples and specimen collected from other diners and restaurant workers, health officials found no trace of the bacteria that were responsible for causing the disease.

Doctors speculated that the patient had a weak immune system and therefore increased his risks of getting infected through consuming contaminated raw marine fish.

Cholera is an acute intestinal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae.

It has a short incubation period, from less than one day to five days, and causes a copious and watery diarrhea that can quickly lead to severe dehydration.

Therefore, it is suggested that people with poor immune system, chronic diseases such as diabetes and patients with kidney, liver or stomach diseases should avoid raw seafood and even uncooked vegetables.