Typhoid

Typhoid fever is caused by a type of bacteria called Salmonella typhi. 

This is not the same type of bacteria that can cause salmonella food poisoning, but the two are related.

This vaccine is recommended for people who travel.

When someone with the infection has a bowel movement, they may pass stools that contain the salmonella typhi bacteria. If they do not wash their hands properly after going to the toilet, they can contaminate any food they touch. If eaten by another person, they may also become infected. 

It can also be passed out in an infected person's urine. Again, if the person handles food without washing their hands properly after urinating they can spread the infectcion to someone who eats the contaminated food.

In poorer parts of the world levels of sanitation are poor and as such human waste contaminates the water supply. People who drink this water can develop typhoid fever.

Up to 1 in 20 people who survive without being treated will be carriers of the infection. This means the salmonella typhi bacteria continue to live in the carrier's body and can be spread as normal in faeces or urine, but wont have any symptoms of the condition. 

After a person eats or drinks food or liquid contaminated with the salmonella typhi bacteria, the bacteria will move down into their digestive system. The bacteria will then quickly multiply, triggering the initial symptoms such as a high temperature, stomach pain and constipation or diarrhoea.

If a person is not treated, the bacteria can get into the bloodstream, which means they can spread to toher areas of the body. The spread of bacteria out of the digestive system can cause the symptoms of typhoid fever to get worse during the weeks after infection.

If the organs and tissue become damaged as a result of the infection, it can cause serious complications, such as internal bleeding or a section of the bowel splitting open.

Symptoms usually develop 1-2 weeks after a person becomes infected.

With treatment, the symptoms quickly improve within 3-5 days. 

• High temperature
• Headache
• Muscle aches
• Stomach pain
• Constipation or diarrhoea
• Rashes
• Confusion

Complications caused by typhoid usually only occur in people who haven't been treated with appropriate antibiotics, or who have had delayed treatment.

In such cases, about 1 in 10 people experience complications, which usually develop during the third week of infection.

The two most common complications of untreated typhoid fever are:

• Internal bleeding in the digestive system.
• Perforation of a section of the digestive system or bowel, spreading the infection to nearby tissue.

The vaccine is reccomended for people who are travelling in high risk areas:

• Africa
• Central America
• Indian subcontinent
• Middle East

Two main vaccines are available:

• Vi vaccine - a single injection.
• Ty21a vaccine - three capsules to take on alternate days. 

There are also combined typhoid and hepititis A injections available for people aged 15-16 or older.

No vaccine offers 100% protection against typhoid fever, but the Vi vaccine is generally more effective than the Ty21a vaccine. 

As the Ty21a vaccine contains a live sample of salmonella typhi, it is not suitable for people who have a weakened immune system, such as people with HIV. It is also not usually recommended for children under 6, whereas children can have the Vi vaccine from 2 years old.

The protective effect of the Vi vaccine will last fro around 3 years, after which a follow-up booster is required. The Ty21a vaccine will last for around a year before a booster dose is required. 

It should be given at least one month before you travel.

Some people experience soreness, redness, swelling or hardness at the injection site. About 1 in 100 experience a fever.

Less common side effects include:

• abdominal pain
• headache
• feeling sick
• diarrhoea

Severe reactions are rare.