How to prevent cholera virus when cholera cases are found in Wuhan University?

Cholera is an acute secretory diarrhea disease, which is caused by the toxin-producing strain of Vibrio cholerae, a gram-negative bacterium. Severe cholera is characterized by massive loss of body fluids and electrolytes through stool and rapid hypovolemic shock (usually occurring within 24 hours after vomiting and diarrhea begin). Appropriate rehydration therapy can reduce the mortality rate of severe cholera patients from more than 1% to less than .5%.

Vibrio cholerae has diversity, including pathogenic and non-pathogenic variants. Only Vibrio cholerae strains that produce cholera toxin can cause cholera. People classified Vibrio cholerae by serology; Among more than 2 serogroups found, only two serogroups have caused cholera epidemic, namely Vibrio cholerae O1 and O139.

global distribution of cholera

cholera mainly occurs in areas where clean water and sanitation facilities are not fully available. Cholera is endemic in about 5 countries, mainly in Africa and Asia, and has caused widespread epidemics throughout Africa, Asia, the Middle East, South America, Central America and the Caribbean (Figure 1). For example, the strains that caused the cholera outbreak in Haiti in 21 subsequently caused cholera outbreaks in neighboring Dominica, Cuba and Mexico.

Figure 1

Cholera cases in resource-rich areas are usually imported cases, which occur after visiting areas where cholera is endemic or epidemic.

The spread of cholera

Humans are mainly infected with Vibrio cholerae by ingesting contaminated food or water. In endemic areas, water is an important storage place for Vibrio cholerae. Because Vibrio cholerae can live on the surface of crustacean plankton, filtering water with coarse cloth can reduce the incidence of cholera in endemic areas.

Although contact with Vibrio cholerae in the environment plays an important role in the spread of cholera, direct human-to-human transmission also plays a certain role. As many as 11-112 Vibrio cholerae can be excreted in the feces of patients with severe cholera. Compared with the Vibrio cholerae isolated from water environment, the Vibrio cholerae recently discharged by infected people seems to be more infectious for the time being. The mathematical model shows that the human-to-human transmission of ultra-infectious Vibrio cholerae excreted by human body is very important for the rapid spread of cholera during the epidemic period.

clinical manifestations of cholera

Vibrio cholerae infection can lead to a series of disease manifestations ranging from asymptomatic intestinal colonization to severe diarrhea. Although the light cases infected by Vibrio cholerae may not be clinically distinguished from watery diarrhea caused by other reasons, the body fluids and electrolytes in severe cholera are lost rapidly, which makes it completely different from watery diarrhea caused by other reasons.

In the early stage of the disease, the stool of cholera patients may contain fecal components and bile. However, the characteristic symptom of severe cholera is the discharge of a large amount of rice swill-like stool, which is a kind of watery stool with patchy mucus (Figure 2) and often smells like fish.

Figure 2

Significant hypovolemia and electrolyte abnormality are the most important consequences of severe cholera, which can occur within hours after symptoms appear. Abdominal discomfort, growling and vomiting are also common symptoms, especially in the early stage of the disease.

how to diagnose?

Most cholera cases are diagnosed according to consistent clinical manifestations. Cholera is the possible cause of all patients with severe watery diarrhea (whether accompanied by vomiting or not), especially those with rapid and severe volume deficiency. Although many different microbial pathogens can cause hypovolumic diarrhea in young children, Vibrio cholerae is the main cause in older patients with such manifestations. Cholera can be diagnosed by using specific selective medium for stool culture and isolating Vibrio cholerae. In the absence of conditions for stool culture, stool test paper or dark field microscopy can be used to support the diagnosis.

how to treat it?

1. Fluid replacement therapy

Active fluid replacement is the basis of cholera treatment. According to the degree of insufficient volume and the evaluation of continuous loss of body fluids, the type and amount of liquid to be given are determined (Table 1). Patients with severe hypovolemia or shock need rapid rehydration, so they should be rehydrated intravenously, and other patients can be rehydrated orally. Patients with severe cholera usually need an average of 2mL/kg of isotonic oral or intravenous fluid in the first 24 hours of treatment, and some patients may need more than 35mL/kg of fluid.

Table 1

2. Antibiotic treatment

Antibiotics can shorten the time of diarrhea, reduce the amount of liquid lost in feces, and shorten the time of Vibrio cholerae excretion. For the suspected or confirmed cholera patients with moderate to severe volume deficiency (Grade 2B), we suggest antibiotic treatment. During the cholera epidemic (Grade 2C), we also recommend antibiotic treatment for suspected or confirmed patients. Oral antibiotics are usually given after initial rehydration therapy and when the patient no longer vomits.

The antibiotics available for cholera treatment include macrolides, fluoroquinolones and tetracyclines (Table 2). Choose available drugs according to the local antibiotic resistance model.

Table 2

Like acute diarrhea of other causes, adequate nutrition is very important to prevent malnutrition in cholera patients and promote the recovery of gastrointestinal function. In addition, zinc and vitamin A supplementation may be beneficial to children with acute diarrhea.

how to prevent it?

The supply of clean water and proper sanitation facilities are the basis of cholera prevention. In addition, it has been confirmed that the protective efficacy of two international oral cholera vaccines in areas with high risk of cholera outbreak can reach 6%-8%. In areas where cholera is endemic or where there is a high risk of cholera epidemic, it may be particularly useful to include these vaccines in cholera prevention plans.

The contents of this article are only for learning and communication, and cannot be used as the basis for clinical diagnosis and treatment.