How do you get these infections?
You get these infections from other infected people by eating or drinking contaminated food or water. The germs (bacteria) are passed out in the stools (faeces) and urine of infected individuals.

They can get into food and water because people who handle food (such as cooks or restaurant workers) may not know that they are infected. It is possible to have typhoid or paratyphoid fever but to have no symptoms or signs of the infection. Humans are the only carriers of these infections.
Typhoid and paratyphoid fever are not passed on by animals.

How do typhoid and paratyphoid fever make you ill?
The germs (bacteria) enter your body through the gut. They sit in your immune system (glands and lymph vessels) and multiply there. They then enter the bloodstream, which is when most people experience symptoms of headache and high temperature (fever).
Through the bloodstream they enter various organs, particularly the liver, spleen, gallbladder and bone marrow. Because bile produced by the gallbladder is squirted into the gut, the bowels then get infected again.

Symptoms of typhoid fever
The incubation period is the time from ingesting the germs (bacteria) until the time you actually start to feel ill. It depends on how many bacteria you have swallowed.
It is usually between seven and fourteen days, but can be as short as three days, or as long as 30 days.

Untreated, the illness usually lasts for three to four weeks, but may be longer in a small number of cases. Symptoms vary from mild to severe and life-threatening.
Lack of fluid in the body (dehydration) is a risk.

About 1 in 300 people infected with typhoid fever may have a low-grade infection. They may not develop any significant symptoms, and then become carriers of the disease.

Raised temperature (fever) and headache are the most common symptoms. Typically, the temperature increases gradually day by day during the first week. People usually experience raised temperature mostly in the evenings.
Rash (rose-coloured spots which lose their colour with pressure).
Stomach pains.
Loss of appetite.
Diarrhoea – more common in children.
Severe constipation – more common in adults.
Feeling sick (nausea).
Cough.
The typical pattern of illness consists of four stages, each lasting about a week. Over the course of these stages, you become tired and may lose weight dramatically.

In the first week, the body temperature rises slowly, and may go up and down, with headache, cough and feeling unwell. Nosebleeds are common.

In the second week there is a high fever of around around 40°C (104°F) – often worse in the afternoon – although the pulse is often slower than expected with a high fever. Some patients get ‘rose spots’ on the lower chest and stomach. Some patients become confused (‘delirious’) with the fever, which earned typhoid the name ‘nervous fever’. Tummy pain and diarrhoea are common, and stools (faeces) are often green. There may be swelling of the liver and spleen, which your doctor may be able to feel.

In the third week of typhoid fever, serious complications can occur (see below).
By the end of third week, the fever starts subsiding. This carries on into the fourth and final week.

Symptoms of paratyphoid fever
Paratyphoid fever is similar to typhoid; but it tends to come on more quickly, have milder symptoms, and last for a shorter time.

Early symptoms can be vague chills, sweating, headache, weakness, cough, loss of appetite, sore throat, dizziness, and muscle pains. These are frequently present before the onset of fever.

Symptoms of paratyphoid are of:

Persistent fever.
Headache.
Tummy (abdominal) pain (in about a third of patients).
Feeling unwell.
Loss of appetite.
Dry cough (this occurs early).
Slow heart rate.
Swelling of the liver and spleen.
Rosy spots on the central body (in about a third of patients).
Constipation (more common than diarrhoea).
Very rarely, patients can suffer mental disorder (psychosis), confusion, and seizures.

What are the possible complications?
About 1 in 10 people with typhoid or paratyphoid fever infections have complications. These can occur at any time while you have the infection, even if you have a mild infection.

The two most common complications are bleeding from, and rupture of, the bowel. These occur in about 2 in 100 cases. These may be life-threatening and may require a surgical operation.
Infection of the heart muscle (myocarditis) occurs in up to 1 in 20 cases. It is a significant cause of death in areas where typhoid and paratyphoid fever are commonly found.

Infection of the nervous system (encephalitis) can cause severe confusion, epileptic seizures and mental health disturbances.

Liver and gallbladder infection may cause yellowing of the skin and the whites of the eyes (jaundice) and severe tummy (abdominal) pain.
Inflammation of the pancreas (pancreatitis) is very rare. This can cause severe pain in the stomach or back, and indigestion.
Kidney failure (in which the kidneys no longer clear toxins from the blood) is also uncommon.
Abscesses around the body.
Lack of fluid in the body (dehydration).
Uncommonly, a fall in the platelet cells in the blood which leads to bruising and bleeding.
Note: if you have any new symptoms, or feel worse while you are being treated for typhoid, you should contact your doctor as soon as possible.

When to seek medical advice
Be aware if you or your child have travelled to an area known to have a risk of typhoid infections, or have been in a situation where hygiene has been poor. If you experience headache, high temperature (fever), tummy (abdominal) pains, cough or diarrhoea you should seek medical advice. This is the case even if you have been vaccinated against typhoid fever, as vaccination does not guarantee complete protection.

How are typhoid and paratyphoid fever diagnosed?
Your doctor will take note of where you travelled, the conditions you stayed in and what you did while you were there. He or she will ask about your symptoms, and will examine you. These are all very important, as it is very difficult to find typhoid and paratyphoid fever in the body, even if you have these infections.

Tests your doctor may carry out
Stool (faeces), blood and urine samples are sent to the laboratory for culture (in which the germs (bacteria) are helped to reproduce and be identified). This test may fail to identify about one third of cases of even whether the bacteria are there. It may also take some days for results to come back.

Widal’s test – this is a blood test which checks for proteins (antibodies) which help to fight S. typhi or S. paratyphi. Again, however, this may miss about one third of cases.
Bone marrow aspiration – a needle is used to take sample of bone marrow fluid. A bone marrow sample is positive in 90% of cases if it is taken during the first week of the illness. It may be more difficult to find after that.

If your travel history and symptoms suggest that you have typhoid or paratyphoid fever, the doctor may start treatment before the results of the tests are available.