Dengue fever is an infectious viral disease transmitted by mosquitoes in tropical and sub-tropical climates. Most people with dengue fever suffer unpleasant symptoms, such as fever, headache and vomiting, but will make a full recovery. However, repeated infections can result in a form of haemorrhagic fever.…
What is cholera?
Cholera is an infectious bacterial disease that causes severe diarrhea in the people it infects. It has been responsible for several epidemics throughout history and has been affecting humanity for centuries. Originating in the Indian subcontinent, cholera has spread throughout the world, but is mostly found in areas with poor sanitation.
In many countries, cholera is a common occurrence. In others, cholera outbreaks may occur only when sanitary conditions are particularly bad, or when a new, virulent strain of the bacterium arrives. Global cholera pandemics have swept the world in the past, the most recent one occurring in the early 1990s. Today it is still a serious health concern globally and a leading cause of death, particularly among young children.
The cause of cholera is the Vibrio cholerae bacterium. It is passed between people via food or the water supply that are contaminated with human stools (feces).
After the bacteria are swallowed, most of them are killed by the acids in the stomach. The bacteria that manage to make it past the stomach settle in the small intestine and release a toxin. The toxin causes the intestine's cells to expel large amounts of water, resulting in massive, watery diarrhea.
Risk factors for cholera include:
You may be at increased risk of contracting cholera if you are living in, or traveling to, places where cholera can be found. These include:
- Countries and areas including India, Africa, South and South-East Asia, South America and Central America and the Caribbean;
- Places where sanitary conditions are poor due to natural disaster, war, civil strife or other emergencies, and;
- Refugee camps and other places where people live in crowded conditions without adequate sanitation measures.
In the abovementioned places, any exposure to untreated water can lead to infection from the following sources:
- Drinking water;
- Uncooked fruits and vegetables, such as salads;
- Iced drinks and ice-cream;
- Brushing teeth, and;
- Eating any water-sourced food (such as fish and shellfish) that is not cooked properly.
Signs and symptoms
Many people who catch cholera will not experience any symptoms at all, or only mild ones. Only about 5-10% will develop major symptoms of the disease. 
Signs of a cholera infection include:
Methods for diagnosis
The diagnosis of cholera can be confirmed by assessing an infected person's stool for the Vibrio cholerae bacteria. This can be performed in the following ways:
A stool sample can be examined under the microscope for the presence of cholera bacteria.
Rapid diagnostic test
A rapid test of a stool sample using a special dipstick can be used to provide the healthcare professional with a quick diagnosis of cholera.
A stool sample may also be grown as a stool culture on a special nutrient gel. It is slower than both the previous tests, but provides a more reliable diagnosis and can identify the specific bacterial type.
Types of treatment
The greatest danger of cholera is the dehydration it causes. Therefore, the key to treatment is the replacement of water and electrolytes. The most effective treatment for a person infected with cholera is known as the oral rehydration solution (ORS). Developed during the 1960s and 1970s, it should be credited for saving more lives than any other medical development since the advent of vaccinations.
ORS is a small packet of salts and sugars (sodium and glucose) that is dissolved in clean water and given to the person with cholera. It is a cheap and effective treatment - as long as clean water is available for its preparation.
In an emergency, a home-made version of the ORS can be prepared using six level teaspoons of sugar and half a teaspoon of salt dissolved in a liter of clean water. This can prevent dehydration until professional medical treatment is available.
Another effective way to treat dehydration and replace water and electrolytes is with intravenous fluids.
Normally, the body's immune system clears the body of the infection within a few days. For severe cases of cholera, antibiotic treatment can accompany rehydration. It has been shown to aid recovery.
One study showed that treating young children with zinc tablets reduced the severity of their diarrhea.
The severe diarrhea that affects people with cholera depletes the body of water and solutes. This can cause dehydration, kidney problems and death.
If treated quickly and effectively, a person suffering from cholera can recover quickly and completely, and experience no long-term problems. After they recover they do not continue carrying the bacterium, but can be reinfected in the future if exposed again.
Steps you can take to prevent being infected when in an area where cholera is present:
- Drink only treated or bottled water;
- Avoid any other contact with untreated water;
- Eat only cooked food from trusted sources, and;
- Avoid seafood, shellfish, raw fruits and vegetables.
On a global level, preventing illness and death from cholera is mostly a matter of providing good sanitation and clean water to as many people as possible.
A vaccine for cholera is available. It is taken as a drink in two doses and is about 60-90% effective.  The vaccine's effect lasts only 2-3 years and only about six months in young children. It is recommended mainly for people who expect to be exposed to cholera in the near future.