The initial symptoms of rabies are mild, but they quickly become serious.
The incubation period
The incubation period is the time it takes for symptoms to develop after a person is infected with the virus. The incubation period for rabies is usually two to 12 weeks, although it can be as short as four days. It would be highly unusual for the incubation period to last for more than a year.
The closer the site of infection is to your brain, the shorter the incubation period. For example, a bite to your face, head or neck will have a shorter incubation period than a bite to your arm or leg.
The length of the incubation period is important because it is the only period in which treatment can be successful.
The initial symptoms of rabies are often vague, and it can be easy to mistake them for other less serious types of infection. They include:
- a high temperature of 38ºC (100.4ºF) or above
- fatigue (extreme tiredness)
- problems sleeping
- lack of appetite
- sore throat
Around half of people will also experience pain and a tingling sensation at the site of the infection.
Initial symptoms of rabies last for two to 10 days before more severe symptoms start to develop. There are two types of advanced rabies:
- furious rabies, which accounts for four out of five cases
- dumb or paralytic rabies, which accounts for the remainder of cases
Furious rabies is characterised by episodes of increasingly odd and hyperactive behaviour, separated by periods of relative calm. During these episodes a person may have some or all of the following signs and symptoms:
- aggressive behaviour, such as thrashing out or biting
- hallucinations – seeing or hearing things that are not real
- delusions – believing things that are obviously untrue
- excessive production of saliva
- high temperature (fever)
- excessive sweating
- the hair on their skin stands up
- a sustained erection (in men)
People with furious rabies will also develop hydrophobia (a fear of water). This initially begins as a pain in the throat or difficulty swallowing. On attempting to swallow, the muscles in the throat go into a brief spasm that lasts for a few seconds. Subsequently the sight, sound or even the mention of water (or any other liquid) can trigger further spasms. There will also be fear of bright light (photophobia) and fear of breezes (aerophobia).
A few days after these symptoms develop, the affected person will fall into a coma and die, usually as a result of heart or lung failure.
Dumb or paralytic rabies
Dumb rabies, sometimes called paralytic rabies, is characterised by muscle weakness, loss of sensation and paralysis (inability to move one or more muscles). This usually begins in the hands and feet before spreading throughout the body.
Hydrophobia is unusual in cases of dumb rabies, although muscles may go into spasm. As with furious rabies, someone with dumb rabies will fall into a coma and eventually die from heart or lung failure.
When to seek medical advice
If you are in a part of the world known to be affected by rabies, always seek medical advice as soon as possible if you are bitten or scratched by an animal, particularly a dog. You can also catch rabies if you have an open wound that is licked by an infected animal.
If you don't seek medical help while abroad, you should do so as soon as you are back in the UK.
In the UK, rabies is almost non-existent. However, always seek medical attention if you are bitten by a bat, or if you suspect someone in your care who is unable to report a bite may have been bitten (for example, if you find a bat in a young child's room).
Symptoms of rabies in an animal
As with humans, the symptoms of rabies in an animal follow a number of stages.
The first stage is marked by initial vague symptoms, such as:
- loss of appetite
- a change in normal behaviour, such as appearing unusually tame around strangers
The second stage is known as the "mad dog" stage and usually lasts for two to four days. It is characterised by aggressive and erratic behaviour, such as:
- constantly barking or growling
- no fear of normal natural enemies
- attempting to attack and bite anything that comes near, including inanimate objects
The final stage, known as the "paralytic" stage, lasts for two to four days and is characterised by symptoms such as:
- the animal appearing to be choking
- foaming at the mouth
- the dropping of the lower jaw (in dogs)
- paralysis of the jaw, mouth and throat muscles