Typhoid fever

Typhoid is caused by a form of Salmonella

Typhoid fever is a life-threatening illness which is caused by bacteria.

It is typically passed from person to person through food and drink or by drinking from contaminated water supplies.

It is not particularly prevalent in industrialised countries but is still common in the developing world where there are about 17m cases each year.

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What causes it?

Typhoid fever is caused by the bacterium Salmonella Typhi.

Once inside the bowel, the bacterium penetrates the lining of the intestines, and reaches the underlying tissue.

If the immune system is unable to stop the infection here, the bacterium will multiply and then spread to the bloodstream.

People catch typhoid fever by eating food or drinking beverages that have been handled by a person carrying the bacteria.

It can also be caught by drinking water contaminated by the bacteria or eating food washed with contaminated water.

Water is contaminated where there is inadequate sewerage systems and poor sanitation.

What are the symptoms?

The incubation period is 10 to 20 days and depends on, among other things, how large a dose of bacteria has been taken in.

The body can usually cope with a mild infection, and successfully rids itself of the bacteria, which produce only mild symptoms.

However, a more serious infection produces severe illness, usually in two phases.

Initially, the patient's temperature rises gradually to 40C. This is likely to be accompanied by sweats, a loss of appetite, coughing, headache, increasing listlessness and possibly constipation and skin rashes

Children often vomit and have diarrhoea.

The second phase of the illness usually kicks in during the second and third weeks.

The fever remains very high and the pulse becomes weak and rapid.

The constipation is replaced by severe diarrhoea, which may contain blood.

It is not until the fourth or fifth week that the fever drops and the general condition slowly improves.

Even when symptoms disappear, people can still carry the bacteria and pass it on.

In some cases the disease, if left untreated, typhoid may lead to dangerous complications such as perforation or bleeding of the intestine, and pneumonia.

What is the treatment?

Antibiotics are used to treat typhoid fever and a person usually begins to recover after two or three days.

Vaccinations to protect people against typhoid fever are also available and usually given to westerners travelling to countries where it is found.

How deadly is it?

Typhoid can lead to dehydration, which can be deadly, as the body's major organs cannot function without adequate fluid and salt levels. In addition, the complications of the disease can be life-threatening.

Without treatment one in 10 people die but if people are given antibiotics the chances of dying lessen to one in 100.

Everyone is at risk from typhoid but children are particularly susceptible.

Do the conditions following the Indian Ocean tsunami make typhoid more likely?

Yes. Unless fresh water supplies and purification equipment reaches the areas affected by the tsunami typhoid is a very real risk.

The bacteria could contaminate the water supply because sewage systems have been disrupted and the normal controls over food and water have been lost.