Two cases of serious bacterial infection on Macau beaches

The Health Bureau (SSM) has reported two recent cases of serious bacterial infection on two local beaches, Cheoc Van and Hac Sa.

The infections were caused by the bacterium Vibrio vulnificus, a pathogenic bacterium of the genus Vibrio, present in marine environments such as estuaries, brackish ponds, or coastal areas and related to Vibrio cholerae, a causative agent of cholera.

According to the SSM, the first case was reported on Sept. 11, when a man reported being stung by a fish fin while swimming at Cheoc Van.

The sting occurred on his left index finger and after a few hours, he developed symptoms such as swelling and fever.

After being treated at the Conde de São Januário Hospital Center (CHCSJ), the patient noted the condition had worsened the next day, and the swelling and pain had extended to the palm of the left hand. At the same time, a necrotizing soft tissue infection was diagnosed, with the patient being admitted to the hospital.

After laboratory analysis on Sept. 18, the existence of Vibrio vulnificus bacteria in wound secretions was confirmed.

A few days later, on Sept. 26, another Macau resident reported having been stung on his left foot while walking barefoot at Hac Sa beach.

As in the previous case, this second person also developed swelling and fever and on the following day, saw his doctor at a local clinic.

The physician immediately referred the patient to the CHCSJ where he was diagnosed with a necrotizing soft tissue infection of the left lower limb and was admitted to the hospital for medical treatment.

As in the first case, laboratory analysis confirmed the presence of the same bacteria.

According to SSM, both patients are in a stable condition and recovering.

According to academic studies reviewed by the Times, although the bacteria exists naturally in low concentrations in warm seawaters, high concentrations able to cause severe infections are usually related to discharges of sewage or untreated wastewater.

“Vibrio vulnificus is a naturally occurring, potentially lethal pathogen found in coastal waters, fish, and shellfish. Sewage spills in coastal waters occur when infrastructure fails due to severe storms or age, and may affect bacterial populations by altering nutrient levels,” a study by James W. Conrad and Valerie J. Harwood published in February 2022 concluded, noting that the “addition of 1% sewage to estuarine water caused the density of a pure culture of V. vulnificus CMCP6 and a natural V. vulnificus population to increase significantly, by two to three orders of magnitude.”

The same authors and others have concluded the effects of environmentally relevant levels of sewage on V. vulnificus populations and gene transcription suggest that sewage spills that impact warm coastal waters could lead to an increased risk of V. vulnificus infections.

While the cause of the current outbreak is unclear, experts have warned that the presence of significant quantities of this bacteria could be extremely concerning not only for beachgoers but potentially for everyone, especially now while Macau is being affected by several weather phenomena like typhoons and astronomical tides which often cause flooding in the low-lying areas.

In the report, the SSM also noted that “if a wound comes into contact with seawater containing V. vulnificus or, a person eats contaminated seafood, it can cause infection.”

“Infections caused by V. Vulnificus through wounds can be mild, but can also cause necrotic fasciitis, with extreme pain, redness, swelling and rapid tissue necrosis,” it said.

The same health authority noted that statistics show that people with necrotic fasciitis may need limb amputation to save their lives, with about 20 to 30% of cases revealed to be fatal.

The consumption of shellfish contaminated by the bacteria can cause diarrhea, vomiting and abdominal pain, with generally no serious consequences.

However, if the infected person has other chronic illnesses, especially liver-related disease and diabetes, sepsis can occur, with symptoms including fever, chills, decreased blood pressure, the appearance of blisters on the skin, and, in the most serious cases, can result in death.

So far, the authorities in charge of local coastal waters have not issued any statements or warnings to the population regarding this case, with the beaches being completely open to the population.