Humans become infected incidentally but, once infected, can act as vehicles for spread. Ingestion of water contaminated by human feces is the most common means of acquisition of V. cholerae. Consumption of contaminated food in the home, in restaurants, or from street vendors can also contribute to spread.
Cholera is a toxin-mediated disease. Its characteristic watery diarrhea is due to the action of cholera toxin (CTX), a potent protein enterotoxin elaborated by the organism following its colonization of the small intestine.
It passes through 3 phases: Evacuation (profound watery diarrhea), collapse (hypovolemic shock) and recovery phases.
After a 24- to 48-h incubation period, cholera begins with the sudden onset of painless watery diarrhea that may quickly become voluminous and is often followed shortly by vomiting. In severe cases, stool volume can exceed 250 mL/kg in the first 24 h. If fluids and electrolytes are not replaced, hypovolemic shock and death ensue. Fever is usually absent. Muscle cramps due to electrolyte disturbances are common. The stool has a characteristic "rice-water" appearance because of its resemblance to the water in which rice has been washed.
The clinical suspicion of cholera can be confirmed by the identification of V. cholerae in stool; however, the organism must be specifically sought. In experienced hands, it can be detected directly by dark-field microscopy on a wet mount of fresh stool, and its serotype can be discerned by immobilization with Inaba- or Ogawa-specific antiserum.
Cholera is simple to treat; only the rapid and adequate replacement of fluids, electrolytes, and base is required. Oral rehydration solution (ORS) with the WHO formulation forms the standard of therapy.
For initial management of severely dehydrated patients, intravenous fluid replacement is preferable, if available. Because profound acidosis (pH < 7.2) is common in this group, Ringer's lactate is the best choice among commercial products. It must be used with additional potassium supplements, preferably given by mouth.
Although not necessary for cure, the use of an antibiotic to which the organism is susceptible will diminish the duration and volume of fluid loss and will hasten clearance of the organism from the stool. Single-dose tetracycline (2 g) or doxycycline (300 mg) is effective in adults.