What is typhoid fever?
Typhoid fever is an infectious feverish disease, with severe symptoms in the digestive system in the second phase of the illness (Paratyphoid is a milder disease caused by a related bacteria (there is no vaccine for paratyphoid).
The French used to call the disease a 'boil of the intestine'. That 'boil' can burst and led to death.
Classic typhoid fever is a serious disease. It can be life-threatening, but antibiotics are an effective treatment and the vaccine can be preventative.
The disease lasts several weeks and convalescence takes some time.
The disease is transmitted from human to human via food or drinking water, and it's therefore mainly hygiene and sanitary conditions that determine its spread.
It's rarely seen in Europe, and 94 per cent of imported cases are from the Indian subcontinent.
In the UK, Public Health England data indicates sources of infection as mainly India and Pakistan.
What causes typhoid fever and paratyphoid fever?
Typhoid fever is caused by an infection with a bacterium.
This bacterium has different names in different places (UK experts prefer the name Salmonella enterica, serovar Typhi, but the US may still call it Salmonella Typhi). It's only found in humans and may lead to serious illness.
When the bacterium passes down to the bowel, it penetrates through the intestinal mucosa (lining) to the underlying tissue.
If the immune system is unable to stop the infection here, the bacterium will multiply and then spread to the bloodstream, after which the first signs of disease are observed in the form of fever.
The bacterium penetrates further to the bone marrow, liver and bile ducts, from which bacteria are excreted into the bowel contents.
In the second phase of the disease the bacterium penetrates the immune tissue of the small intestine, and the often-violent small-bowel symptoms begin.
Paratyphoid fever is caused by Salmonella Paratyphi, a similar and generally milder disease.
The term 'murine typhus' is used for salmonella in animals.
How is typhoid fever spread?
Salmonella Typhi can only attack humans. So, the infection always comes from another human, either an ill person or a healthy carrier of the bacterium.
The bacterium is passed on with water and foods and can withstand both drying and refrigeration.
As it's necessary for someone to be exposed to a certain quantity of bacteria before symptoms occur, the storage of foods is also of great significance.
They must be kept refrigerated and prepared correctly, as required by general hygiene, so that any bacteria present are not able to multiply significantly.
Where does typhoid fever occur?
Typhoid fever is not a tropical disease and is related to hygiene and sanitary conditions rather than the climate itself.
Typhoid fever is found in large parts of Asia, Africa, Central and South America, where it occasionally causes epidemics.
The WHO estimates that there are approximately 17 million cases a year, which result in 600,000 deaths. Many of those infected get the disease in Asian countries.
What are the symptoms of the disease?
The incubation period is 7 to 21 days and depends on, among other things, how large a dose of bacteria has been taken in.
In the mild disease, the bacterium is eliminated very early in the course of the disease and there are perhaps only mild symptoms. It's possible to become a healthy carrier of infection (like the famous Typhoid Mary, a New York cook).
There are two phases of classic typhoid fever:
- 1st phase: the patient's temperature rises gradually to 40ºC, and the general condition becomes very poor with bouts of sweating, no appetite, coughing and headache. Constipation and skin symptoms may be the clearest symptoms. Children often vomit and have diarrhoea. The first phase lasts a week and towards the end the patient shows increasing listlessness and clouding of consciousness.
- 2nd phase: in the second to third weeks of the disease, symptoms of intestinal infection are manifested and the fever remains very high and the pulse becomes weak and rapid. In the third week, the constipation is replaced by severe pea-soup-like diarrhoea. The faeces may also contain blood. It's not until the fourth or fifth week that the fever drops and the general condition slowly improves.
Intestinal perforation or profuse bleeding from the intestinal mucosa may occur if typhoid fever is left untreated.
There are good prospects of cure with antibiotics, and the patient can be discharged from hospital when the general condition is stable.
But good general hygiene (as always) should be maintained in the home because bacteria may continue to be excreted for several more weeks.
If the patient is a food handler, they'll need to stay off work until at least two stool samples show absence of the infection.
What can you do yourself?
- There are several forms of vaccine that protect against Salmonella Typhi. Most UK travel clinics use the injectable form (Typherix or Typhim Vi), rather than the oral form preferred in the USA (Vivotif). The injectable vaccine is easier to administer, since it only requires one dose and has less side-effects. It should be administered at least two weeks prior to potential typhoid exposure and is effective for three years.
- The routes of infection depend on hygiene conditions, and general kitchen hygiene should be maintained to prevent infection. For travel, the same precautions can be taken as described under cholera.
How is the disease diagnosed?
The clinical picture together with information on travel may be a good pointer for the doctor in moderate to severe cases. For the final diagnosis to be established, the bacteria have to be detected in samples from the stool, blood or other tissue.
A serology test (Widal) not much used in the UK can be very useful overseas in areas where the infection is more common but in can be inaccurate.
Malaria also needs to be considered as another possible explanation for the symptoms of the disease when the patient has been travelling in a malarial area.
How is typhoid fever treated?
Treatment may require admission to hospital, and loss of fluid and salt is treated with fluid therapy as appropriate.
The bacterium is controlled with antibiotics, and in rare cases steroid medicines are also included in the treatment.
Within the hospital setting, infected people are cared for in isolation. Proper hand hygiene is the most important way of preventing further spread in hospital.
Stool samples are also taken from members of the patient's family to identify any 'healthy' carriers.