Three Cases of “Flesh-eating”

Bacterial Infections in Hong



Three cases of necrotizing fasciitis— an infection caused by bacteria that destroys skin, fat, and the tissue covering the muscles in a short period of time—have been reported in Hong Kong during the month of July in 2015. Similar sporadic cases have also been reported in April and August of 2015 in Hong Kong. The affected include: an 82-year-old man and 78-year-old woman with underlying chronic illnesses and a 59-year-old man with good past health.


The causative agent is a rare but deadly pathogen, Vibrio vulnificus and its name literally translates to “causing wounds” in Latin. V. vulnificus is one of the three major species of Vibrio, with the other two being V. cholera and V. parahaemolyticus both of which are pathogens of humans.

Vibrio vulnificus

V. vulnificus is a Gram-negative, lactose-fermenting, opportunistic (similar to L. monocytogenes), and motile curved bacterium commonly found in marine and estuarine environments. It is a moderate halophile (requires salt for growth) and is frequently isolated from oysters, clams, crabs, and other shellfish in warm coastal waters. It is responsible for causing 95 percent of all seafood-related deaths and has a mortality rate of over 50% in North America. The mortality rates varied in Hong Kong, being 35% for septicaemia cases and 20% for wound-infection cases.

V. vulnificus has the ability to cause wound infections, gastroenteritis, or a syndrome known as primary septicemia. Infections among healthy individuals are acute and do not have long-term consequences; ingestion of this bacterium causes mild symptoms such as vomiting, diarrhea, and abdominal pain usually within 16 hours.

In the immunocompromised population however, V. vulnificus can trigger further complications and has the potential to invade the bloodstream from an open wound or from the gastrointestinal tract, causing primary septicemia – a severe and life-threatening illnesses. This disease is characterized by fever, chills, septic shock that is soon followed by death. The three patients affected in Hong Kong had to either undergo amputation or excisional debridement.

V. vulnificus (There are much worse pictures than this one!)

Individuals are considered high-risk and vulnerable to infection if they have underlying chronic diseases or liver diseases [i.e. diabetes, cirrhosis, leukemia, lung cancer, acquired immune deficiency syndrome (AIDS), AIDS- related complex (ARC), or asthma requiring the use of steroid]. They are 80-200 times more likely to develop primary septicemia than healthy individuals.

The infective dose for healthy individuals is unidentified but for immunocompromised persons, septicemia occurs with doses of less than 100 total organisms. The incubation period is 1 – 7 days after eating and the duration of illness ranges from 2 to 8 days. Diagnostic methods are similar to those used to detect common foodborne pathogens and revolve around culturing of the organism from wounds, diarrheic stools, or blood. Methods such as the Quantitative Loop-Mediated Isothermal Amplification can quantitatively detect V. vulnificus in raw oysters with high speed, specificity, and sensitivity.

Measures that can be taken to prevent illness include:
• Avoid going into the ocean with open wounds (I think most people neglect this)
• Avoid eating raw or undercooked shellfish
• Before cooking: Discard any oysters with open shells
• During cooking: Boil for 3-5 minutes after shells open.
• After cooking: Discard any oysters with shells that did not open.

There have been many sporadic cases of V. vulnificus in Hong Kong over the past decade. Although the Centre for Health Protection of Hong Kong offers various Internet resources on how to prevent V. vulnificus infections, many of the victims are the elderly and are less likely to be able to access this information. I believe that more focus needs to be directed to relaying information on opportunistic foodborne pathogens to the elderly and immunocompromised in a manner that is not via the internet, i.e. various clinics and hospitals should offer them pamphlets and communicate with them verbally. In 2013, Health Canada has collaborated with the FAO, WHO, and the government of Japan to produce expert recommendations to the Codex Committee on Food Hygiene regarding V. vulnificus. Appropriate methods to monitor environmental hygiene and hygienic production, etc. can be found in Codex Alimentarius Guidelines on the Application of General Principles of Food Hygiene to the Control of Pathogenic Vibrio Species in Seafood.

Questions for thought:

1. Is this pathogen present in other geographical areas?

2. Which method(s) would be most suitable to detect the presence of this pathogen based on it transmission route?


Codex Alimentarius (2010). International Food Standards. Guidelines on the Application of General Principles of Food Hygiene to the Control of Pathogenic Vibrio Species in Seafood. Retrieved from:

FDA (2015). Vibrio vulnificus. Bad Bug Book: Foodborne Pathogenic Microorganisms and Natural Toxins Handbook. Retrieved from:

Han, F., Wang, F., & Ge, B. (2011). Detecting potentially virulent vibrio vulnificus strains in raw oysters by quantitative loop-mediated isothermal amplification. Applied and Environmental Microbiology, 77(8), 2589-2595.

Lee, S. E., Kim, S. Y., Kim, S. J., Kim, H. S., Shin, J. H., Choi, S. H.. . Rhee, J. H. (1998). Direct identification of vibrio vulnificus in clinical specimens by nested PCR. Journal of Clinical Microbiology, 36(10), 2887-2892.

Ma, J (2012). Vibrio vulnificus in food. Food Safety Focus, 72. Retrieved from:

Stone, J. (2015). With Global Warming, Expect More Deadly Vibrio Cases. Pharma & Healthcare. Forbes. Retrieved from:

Treasury Board of Canada Secretariat (2015). Food and Consumer Safety Action Plan. Retrieved from:

Vibrio vulnificus (2013). Vibrio Illness (Vibriosis). Centers for Disease Control and Prevention. Retrieved from: