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Rabies

Published by Bupa's health information team, August 2008.

This factsheet is for people who would like information about rabies.

Rabies is a viral infection that can be spread from animals to people. People usually catch it after being bitten by an infected animal (often a dog).

Rabies is fatal once it develops, but it can be prevented by vaccination if it's given before or soon after infection.

• About rabies
• Symptoms
• Diagnosis
• Treatment
• Prevention
• Further information
• Questions and answers
• Sources

About rabies

Rabies is a viral infection that is spread from animals to humans. It causes inflammation of the brain (encephalitis) and is fatal.

How common is rabies?

According to the World Health Organization (WHO), rabies kills about 55,000 people every year. Most of these deaths occur in rural areas of developing countries, especially in Africa, Asia and South America. Nearly all of these deaths are caused by rabies infections spread by bites from stray dogs.

Rabies is very rare in the UK. The last time someone died from rabies caught in the UK was in 1902. The virus has since been wiped out among wild animals in the UK.

Since 1946, 22 more people have died from rabies in the UK after being infected abroad.

However, a strain of rabies-like virus has recently been found among bats in the UK. In 2002, a bat handler in Scotland died after being bitten by an infected bat. It's extremely rare for this strain of rabies-like virus to spread to humans and the UK still maintains a rabies-free status.

What causes rabies?

The rabies virus is a member of a group of viruses called lyssaviruses that all cause rabies-like disease.

There are currently seven known species of Lyssavirus. The species that causes classical rabies exists mostly in warm-blooded domestic and wild animals.

The rabies virus is found in many areas of world. It exists among wild animals in North America and North Eastern Europe. Across Asia, Africa and South America it is common in stray dogs. Islands such as the UK and Australia are currently rabies free.

The other strains are found mostly in bats and exist in specific regions across the world.

How is rabies spread?

Rabies is a serious infection of the brain and spinal cord (central nervous system or CNS). The virus enters the body either through broken skin or though mucus membranes such as in the mouth or nose. This most commonly happens when a person is bitten by an infected animal, often a dog. The virus can also enter a person's body through a scratch if infected saliva comes into contact with it, for example, through licking.

The virus then enters nearby nerves. From here it gradually travels towards the brain or spine at a rate of about one to 10 cm a day.

When the virus reaches the brain or spine, it then spreads to the rest of the body along other nerves. The virus also enters tissue next to nerves; for example, salivary glands. This causes the virus to enter the saliva - this is why the virus can be spread by bites.

Symptoms

The time it takes for symptoms to appear after a person catches the infection (incubation period) varies hugely, from 7 days to a year or more. The closer the bite is to the head or spine, the shorter the incubation period is likely to be. Bites on the face are usually quickest to lead to rabies, whereas bites on the limbs generally take longer. On average, rabies develops one or two months after being bitten, but in rare cases incubation periods of up to 7 years have occurred.

The first symptom is usually itching, pain or pins and needles in the area that's been bitten. A flu-like illness then develops, with a cough, sore throat, fever, headache and feeling sick or vomiting. These symptoms last between one and four days.

Rabies can develop in two ways: furious rabies and dumb rabies.

Furious rabies

Furious rabies occurs when the virus begins to affect the brain. The infected person will become increasingly agitated, excitable and hyperactive (feeling a need to move all the time). Confusion, hallucinations (seeing or hearing things that aren't there), strange or bizarre thoughts and behaviour and muscle spasms soon follow. This may be accompanied by wild and aggressive behaviour.

These symptoms are often interrupted by periods of normal thoughts and behaviour, but these times become shorter as the disease progresses.

About half of all rabies patients develop hydrophobia, which means a fear of water. A severe pain in the throat develops when trying to drink liquid because the muscles in the neck and stomach contract involuntarily. This might be accompanied by a feeling of terror.

People with rabies often develop hyperaesthesia. This means that you become extremely sensitive to light, noise and touch. Even a gentle breeze can be disturbing - this is called aerophobia.

Rabies also causes excessive saliva production, or hypersalivation. This, combined with the inability to swallow, causes the characteristic foaming at the mouth that happens with the illness.

Eventually a coma develops, and at this stage intensive care treatment is needed to survive. Irregular heart beats, low blood pressure and very high fever may develop. The virus will begin to affect the part of the brain that controls breathing, which will eventually stop to be followed by death.

If breathing support is provided, other problems such as irregular heart beats, low blood pressure, bleeding in the stomach and heart attacks can occur.

Dumb rabies

In dumb rabies your spinal cord is affected. This is less common than furious rabies. It causes muscle paralysis. If the bite is on the arm or a leg, that part is usually the first to become paralysed. The paralysis then gradually spreads to other areas of the body. Once the muscles that aid breathing are affected, the person will need to have oxygen forced into the lungs via a ventilator to stay alive.

Unfortunately, once symptoms begin, rabies is nearly always fatal. However, comprehensive medical care has enabled a few people to survive.

People with rabies tend to die about four days after symptoms start, although some have survived up to 20 days.

Diagnosis

In the early stages, it's impossible to distinguish rabies from other illnesses that cause inflammation of the brain.

If hydrophobia develops, it immediately suggests rabies. Paralysis developing in an arm or a leg a few days after an animal bite would also suggest rabies to a doctor. However, since it can sometimes be a long time after the bite, it isn't always remembered.

A diagnosis of rabies is usually made with the help of laboratory tests.

Tests

There are several tests that might be done to confirm rabies. Body fluids such as saliva and spinal fluid can be examined for antibodies to the virus.

The most accurate way of diagnosing the illness is to take a bit of skin, usually from the neck (a biopsy), and examine it for the rabies antibodies.

Treatment

Once rabies has developed there is no cure, and it is almost always fatal. However, if you have been bitten by an animal with rabies, it is possible to prevent it from developing with anti-rabies vaccines (See Prevention).

Prevention

Before exposure

If you are travelling to a developing country where there is rabies, you may need to have a rabies pre-exposure vaccine.

Having this vaccination means that if you are bitten by an animal with rabies, you have more time to get medical treatment before the disease develops. It could also protect you if you are exposed to the virus without realising it.

Even if you have been vaccinated, you still need to get treatment if you are bitten by an animal with rabies, but you will not need as many injections (see After exposure).

Not everyone needs a pre-exposure vaccination. You should consider a vaccination if you are planning on being there longer than a month, or if you are likely to come into contact with wild animals on your travels. You should also consider a vaccination if you are planning to travel to areas where there is no easy access to hospitals or treatment. People who have a high risk of being exposed to rabies, such as laboratory workers, veterinarians and animal handlers also need to be vaccinated.

When travelling, you should take care to avoid contact with wild animals, especially dogs. Don't pick up any seemingly tame wild animals, and don't attract wild animals by discarding litter.

The rabies vaccine is given as three injections on day 0, 7 and 28 (21 if there isn't enough time before travel). After this you need a reinforcing dose a year later. This needs to be topped up every three or four years, depending on how much risk you are at of getting rabies.

After exposure

If you have been bitten by an animal with rabies, the wound must be carefully washed and flushed with soap and water. After that alcohol or iodine solution should be applied to sterilise it.

You need to get medical help without delay so that human rabies immunoglobulin can be given to you immediately. This is an injection of antibodies that will attack the rabies virus and prevent it from taking hold. It is injected into the area of the wound and into a muscle distant from the bite.

You will also need five doses of the rabies vaccine. This is the same vaccine that is used for pre-exposure prevention (see Before exposure). An injection is given on the day of exposure, followed by four more after three, seven, 14, and 28 days. If you had a rabies vaccine before being exposed to the virus, you only need to have two more doses, on day 0 and 3.

Further information

• Health Protection Agency
  www.hpa.org.uk

 

Sources

• Rabies. Health Protection Agency. www.hpa.org.uk, accessed 27 February 2008
• Rabies. World Health Organization. www.who.int, accessed 27 February 2008
• Rabies. National Travel Health Network and Centre. www.nathnac.org, accessed 6 March 2008
• Kasper DL, Fauci AS, Longo DL, et al., Harrison's Principles of Internal Medicine: McGraw-Hill, 2005: 1156-1160
• Kumar P, Clark M. Clinical Medicine. 6th ed. London: Elsevier Saunders, 2005: 59
• Rabies vaccine information. National Travel Health Network and Centre. www.nathnac.org, accessed 6 March 2008
• Rabies questions and answers. Immunization Action Coalition. www.vaccineinformation.org, accessed 7 March 2008
• Disease factsheet: rabies. Defra. www.defra.gov.uk, accessed 11 March 2008

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Dr James Quekett, Bsc, MB, ChB, MRCGP, DRCOG, DFFP, General Practitioner (GP) and GP Appraiser, Gloucestershire, and by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: August 2008.