Approximately 25% of people who ingest the bacteria actually develop the particular symptoms that we call cholera. Of those, 80% will experience symptoms that are only of mild or moderate severity, while up to 20% will develop severe watery diarrhea that can be life-threatening if not treated properly. The remainder will have no symptoms whatsoever, although they often excrete the bacteria in their stool, which can spread it to others.
It is not known why some people develop cholera while others are unaffected by the bacterial toxin. Most adults in cholera-endemic areas have some antibodies, which helps to protect them from developing the disease. In these countries, severe symptoms are far more common in children and in those who have some additional underlying disease such as AIDS.
Vibrio bacteria are killed by stomach acid. Research has shown that people with low acidity in their stomach (e.g., people taking antacid medications) are much more prone to cholera. Also, people with type O blood seem to be more at risk.
If symptoms of cholera occur, the main symptom is watery diarrhea, which can be severe enough to rapidly drain the body of vital water, salts, and minerals. The first watery stool appears 1 to 3 days after infection, and from then on the body can lose up to one litre of liquid an hour. Vomiting may appear at the same time.
Other symptoms of severe cholera are:
- muscle cramps
- reduced or no urination
- low pulse
- sunken-looking eyes
- wrinkled skin on fingers
Cholera usually runs its course in 3 to 6 days, but if it is not treated it can cause shock from dehydration, kidney failure, coma, and death.