What is cholera?|
Cholera is a bacterial infection which causes diarrhoea and dehydration. In severe cases this can lead to death. The bacteria which causes cholera is vibrio cholerae.
What causes the disease?
Vibrio cholerae is a bacteria which lives naturally in coastal salt water and brackish estuaries. People can become infected by eating seafood from infected areas and then once infected can pass cholera on to others. This occurs by the faecal-oral route. Faeces of people who are infected contain large amounts of vibrio cholerae. If water or food is contaminated by faecal material (this may be from sewage runoff into water supplies or food preparers not washing their hands adequately after toileting) it then becomes infectious. For this reason cholera spreads widely and easily in areas of poor sanitation and low personal hygiene- it is highly infectious and can reach epidemic proportions where much of the population is infected. In Western countries where sanitation is good cholera is largely prevented.
There are two subtypes of cholera - Classical and El Tor. The only significant difference between the two types is that El Tor can cause long-term infection without significant diarrhoea. This means the person who is infected may not be particularly unwell however is capable of infecting others leading to serious disease.
Vibrio cholerae causes diarrhoea by releasing a toxin in the small intestine. This causes large amounts of water and salt (sodium, potassium, chloride and bicarbonate) to pass into the intestine and subsequently be lost as diarrhoea. This is the reason cholera is so dangerous. In severe cases so much water can be lost that the person can die.
These vary considerably depending on the severity of disease. Many people only have a few symptoms and remain relatively 'well' throughout the illness. Others have much more severe symptoms with life threatening disease..
Sudden onset of diarrhoea is the classical presentation of cholera. This usually occurs one to five days after being infected. Typically the diarrhoea is painless, watery and whitish-grey in colour with flecks of white material (mucus) in it. It is often termed as the 'ricewater stool' as it resembles water which has been used to rinse rice. There is no blood and the stool does not smell offensive. The volume of diarrhoea can be enormous. In severe cases 250ml/kg can be lost in the first 24 hours (ie. 20 litres in an 80 kg person).
Vomiting is present in 80% of cases and occurs soon after the onset of diarrhoea. Muscle cramps are common due to the loss of 'salt' in the diarrhoea. It is uncommon for patients to feel feverish.
Loss of salt and water is the most serious problem associated with cholera. The first sign of water loss (other than visualising it in the diarrhoea volume!) is thirst. Following this in order of severity symptoms include dizziness on sitting or standing up, weakness, increased heart rate, decreased urine production, wrinkled skin (like being in the bath too long), decreased consciousness and coma.
In severe cases the complications of cholera include kidney failure and death.
Not every case of cholera is as described. In fact for every person with classical disease as many as ten others will only have minor or mild diarrhoea. It is essential to see a doctor if in a cholera area and the diarrhoea has been severe for two or more days. Or if there is a significant degree of dehydration (from the symptoms listed above) which cannot be corrected by drinking sufficient fluids
1. Cholera is native to the Ganges area in India. However it has spread throughout India, Asia, Central and Western Africa, South and Central America and Southern Europe. There is still a significant risk of acquiring cholera outside these areas if food, water, sanitation and personal hygiene practices are inadequate.
2. Cholera outbreaks occur