"WHO Latest: Vibrio cholerae Spreading Globally Again

According to a Xinhua News Agency report, the World Health Organization (WHO) released a latest report on August 29 local time, stating that due to conflicts and poverty, the global cholera epidemic continues to worsen, with the disease outbreak occurring in multiple countries, posing a major public health challenge to several regions. The report shows that from January 1 to August 17, 2025, a total of over 409,000 cases of cholera/acute watery diarrhea were reported in 31 countries worldwide, including 4,738 deaths, with the case fatality rate exceeding 1% in six countries.

The report states that the ongoing outbreaks in countries such as the Democratic Republic of the Congo, South Sudan, and Sudan since 2024 have continued to spread significantly, complicating the control efforts; while countries like Chad and the Republic of the Congo, which had not reported large numbers of cases for many years, have also experienced renewed outbreaks, overwhelming their already fragile health systems. Data shows that among the regions by WHO, the Eastern Mediterranean Region reported the highest number of cases, exceeding 230,000, while the African Region reported the highest number of deaths, totaling 3,763.

The report indicates that conflicts, large-scale displacement, natural disasters, and climate change have exacerbated the outbreaks, particularly in rural and flood-affected areas with weak infrastructure and limited access to healthcare.

WHO also issued a report on the global cholera epidemic on August 15, noting that despite record-high production of oral cholera vaccines, demand has surged, with over 40 million doses allocated to 12 countries this year. However, due to conflicts and administrative barriers hindering aid access, many affected areas remain unreachable.

WHO emphasizes that safe drinking water, sanitation, and personal hygiene are the only long-term and sustainable solutions to end the cholera emergency and prevent future outbreaks. WHO recommends that countries enhance surveillance, improve case management, strengthen water and sanitation interventions, conduct vaccination campaigns, and engage in cross-border cooperation to coordinate public health measures and prevent the cross-border spread of cholera.

Cholera is a disease caused by the bacterium Vibrio cholerae, which is transmitted through food or water contaminated with the bacterium. The disease has a rapid onset and spreads quickly, with symptoms of diarrhea and vomiting. It is classified as a quarantinable infectious disease internationally.

Structure of Vibrio cholerae

Vibrio cholerae is a Gram-negative, facultative anaerobic bacterium with a short, comma-shaped cell. Its outer layer consists of a typical lipopolysaccharide (LPS) structure, with the O antigen determining the serotype (O1 and O139 are most commonly associated with large-scale outbreaks).

Major Virulence Factors

Cholera toxin (CTX): Encoded by the ctxAB genes, located on the genome of the CTXφ phage. The A subunit catalyzes ADP-ribosylation, persistently activating G proteins, leading to enhanced adenylate cyclase activity, increased cAMP levels, and massive secretion of water and electrolytes, resulting in severe diarrhea. The B subunit forms a pentameric structure that binds to GM1 gangliosides on the host cell membrane, mediating toxin entry.

Zonula occludens toxin (Zot): Disrupts tight junctions in the intestinal epithelium, increasing intestinal permeability and exacerbating fluid loss.

Accessory cholera enterotoxin (Ace): An accessory enterotoxin that exacerbates diarrhea by stimulating chloride ion secretion.

Haemagglutinin/protease (Hap): Involved in adhesion, protein degradation, and colonization.

RTX toxin: A cytotoxin that disrupts the cytoskeleton and interferes with host immune responses.

Pathogenic Mechanism

Cholera toxin (CTX) is the core weapon of Vibrio cholerae. Its B subunit first binds to GM1 gangliosides on the surface of host cells. If cells lack GM1, the toxin may bind to other types of glycans, such as Lewis Y and Lewis X attached to proteins, rather than lipids. The toxin is then internalized and enters the Golgi apparatus and endoplasmic reticulum. Here, disulfide bonds are cleaved, releasing the catalytically active A1 chain. The A1 chain enters the cytoplasm through the endoplasmic reticulum transport channel, refolds, and ADP-ribosylates the α subunit (Gsα) of the trimeric G protein, keeping it in an activated state. As a result, adenylate cyclase is persistently activated, cAMP levels significantly increase, and intestinal cells secrete large amounts of water and electrolytes, ultimately leading to typical "rice-water stools" diarrhea, causing severe dehydration and electrolyte imbalances.

Public Health Significance of Cholera

In China, cholera is classified as a Category A infectious disease, the highest level of statutory infectious disease management. In contrast, the COVID-19 pandemic we recently experienced was managed as a Category B disease in the country, which fully demonstrates the severity of cholera. It not only has broad transmission routes (water, food, and contact can all cause infection) but also has an extremely rapid onset and severe symptoms. Without timely treatment, it can be fatal within hours due to dehydration. The lessons we were taught since childhood, such as "drink boiled water" and "wash hands before meals and after using the toilet," are highly necessary from a public health perspective. Boiling water effectively kills most pathogenic bacteria, including Vibrio cholerae, while good hand hygiene habits significantly reduce oral transmission risks, blocking the "disease entering through the mouth" at its source.