Rabies

Rabies is a zoonotic disease, an infectious disease that can be transmitted from animals to humans. People are bitten (usually by dogs) or the pathogen enters the body through a wound if the skin is damaged.

The term “rabies” is derived from the Latin verb “rabere”, which roughly means “to be mad” or “to rave”. Rabies is caused by viruses known as lyssaviruses, which specialize in infecting nerve cells. The lyssavirus family includes the classic rabies virus.

This infectious disease is common in much of the world. Only a few countries are free from rabies. In Germany and other European countries, systematic measures have successfully eradicated what is known as terrestrial rabies, i.e. rabies occurring in wild animals and domestic animals that live predominantly on the ground. However, illegal imports of domestic animals from regions that are not rabies-free continue to pose a risk. Lyssaviruses are still present in bat populations in Germany.

As a rule, the incubation period for rabies, i.e. the period between infection and the appearance of symptoms, is between 3 and 8 weeks and very rarely less than 9 days. However, there are isolated cases in which several years pass between infection and the development of symptoms. The duration depends on where the person has been bitten. The nearer the bite wound is to the person’s head or spinal cord, the shorter the incubation period.

The course of rabies can be divided into three stages:

Preliminary stage or prodromal stage

At the beginning, rabies is similar to a flu-like illness. Patients feel weak and exhausted. They have a headache and no appetite. Some feel sick and have to vomit. The area around the entry point of the virus is often tender, and the person feels a burning and itching sensation.

Second stage or acute neurologic period

In the second stage, the virus affects the transmission of signals between nerve cells. The nerve cells become overly active and perish as a result.

Medical practitioners make a distinction between two main forms of the disease at this stage. The encephalitic (furious) form of rabies mainly affects the brain. As nerve cells die off, patients lose more and more of their bodily functions. They also show a marked fear of water at this stage. Just hearing or seeing water makes them restless and anxious, and even leads to spasms in the muscles used for swallowing. Because more saliva is also produced, “foaming at the mouth” occurs, where saliva flows out of the patient’s mouth. Some people with the condition are also afraid of drafts. The spasms can spread from the muscles used for swallowing through the whole body. The person’s mood alternates between aggressive and depressed.

The second form of rabies, known as the paralytic form, mainly affects the spinal cord and nerves leading to the muscles and organs. This form of the disease is marked by abnormal sensations or muscle weakness and signs of paralysis that can lead to difficulties with swallowing, but can also affect respiratory muscles.

Terminal stage

In the final stage of rabies, the part of the brain that controls functions such as breathing and the bloodstream fails. The patient falls into a coma. Death usually follows due to paralyzed respiratory or cardiac muscles. A striking feature of rabies is that, in many cases, only a few days pass between appearance of the first symptom and death of the patient.

When an animal has been infected, the viruses replicate in their central nervous system. From there, the viruses also enter their saliva. This is how the disease can then be transmitted to humans – in most cases through bites. The infection can also be transmitted if the saliva is in direct contact with skin wounds or grazes, although this is less common. The virus cannot be transmitted if the skin is intact. Animals such as foxes, dogs and cats can be contagious for 3 to 10 days before they start showing symptoms.

The World Health Organization (WHO) estimates that around 59,000 people die of rabies worldwide every year. However, the actual figure may in fact be much higher due to unreported or undetected cases, especially in Asia and Africa. 

Data on the situation in Europe: 

• Germany has been considered free from terrestrial (classic) rabies since 2008.
• Neighboring countries such as Switzerland, France and the Netherlands also have the “rabies-free” (free from terrestrial rabies) status.
• However, there is a continued risk of infection from bites from wild animals and dogs when people travel to Africa, Asia and South America in particular.
• In 2019 there were four documented cases of rabies in Europe that occurred as a result of such a vacation trip – and all proved fatal. 

If the doctor suspects rabies, they first ask for the person’s previous history. Has the person stayed in a high-risk area? Have they had contact with animals? Have they been bitten? Is the person vaccinated?

If the suspicion of rabies is confirmed, laboratory tests will be undertaken. This involves doctors taking blood and cerebrospinal fluid to detect antibodies that the body produces when it encounters the pathogens. Laboratories can now also use other methods to directly detect the genetic information of the virus, the rabies virus RNA.

However, despite the many advances that have been made in the diagnosis of rabies, the problem remains that there is little to no excretion of the virus from the nervous system into the blood. As a result, a negative test result does not necessarily mean that a patient is not carrying the virus. This is also why it is so important for the doctor to ask the patient lots of detailed questions to help pinpoint a diagnosis.

Large-scale vaccination of pets has already caused the rate of transmission from animals to humans to drop sharply. The vaccination of wild animals such as foxes using vaccination bait has wiped out the virus in much of Europe.

However, there is still a risk from illegally imported animals or those of unknown origin. The local health authority is immediately informed of any suspected contact with a rabid animal or an animal suspected of having rabies.

Animals living in the wild are usually shy of people. However, wild animals often lose their fear of people when they first contract rabies. Particular caution is required if otherwise shy animals exhibit this behavior. The best way for people to protect themselves from transmission is to keep their distance to avoid bites.

A rabies vaccination is available as a preventive measure. The Standing Committee on Vaccination at the Robert Koch Institute recommends vaccination for:

• People who have close contact with bats in their work or for other reasons.
• People who work in laboratories with rabies viruses.
• People who travel to areas where rabies is common.

In the past, the bite of a rabid animal was considered a death sentence. Today it is possible to save the life of a person who has been bitten through timely vaccination administered after the bite (known as post-exposure vaccination). However, if the person already has symptoms, it is too late. Therefore, it is extremely important to see a doctor immediately whenever rabies is suspected.

Treatment generally follows the steps below:

• Wash pathogens out of a bite or scratch wound.
• Immediately and thoroughly clean the wound with water and soap solution.
• If it is a deep wound, it can be flushed with a catheter.
• However, the wound should not be cauterized or stitched up.

People suspected of having rabies are immediately admitted to a hospital’s intensive care unit. If, following these immediate measures, the suspicion of contact with rabies is confirmed, post-exposure vaccination must be started as soon as possible. If this is done immediately, it provides almost full protection against the development of symptoms.

The period between contact with the virus and the appearance of symptoms – known as the incubation period – may last several months, which is why it makes sense to administer a vaccine even at a later stage. This is an important step if, for example, rabies is not suspected immediately or if the vaccine is not available locally. On the other hand, protective vaccination is no longer effective if the incubation period has already progressed and the virus has reached the central nervous system, so that the patient is showing symptoms.

It is difficult to detect rabies viruses in the blood at first. They affect the central nervous system, which is separated from the blood by what is known as the blood-brain barrier. This otherwise very important barrier stops the immune system from “seeing” the virus in time and from being able to develop antibodies. This explains why so much time can pass between infection and the appearance of symptoms in some cases. It also explains why the disease then manifests itself so quickly and violently – because the viruses are able to spread extensively behind the barrier before being detected by the immune system beyond the barrier.

This also means that rabies is one of the few diseases that can still be prevented by timely vaccination even after infection. However, once symptoms appear, it is almost always fatal.

Rabies must be reported. Under § 6(1) No. 1 IfSG (German Infectious Diseases Protection Act), doctors must report to the local health authority the names of patients suspected of having rabies, those who have rabies and those who have died of rabies.

Under § 7(1) IfSG, they must also report the names of any persons in whom they have been able to directly or indirectly detect an acute infection with the rabies virus.

Under § 6(1) No. 4 IfSG, doctors must report the name of any person who has suffered an injury caused by an animal suffering from or suspected of suffering from or suspected of being infected with rabies as well as any contact with such an animal or animal carcass.

If at least one of the criteria applies, the competent local health authority must be informed within 24 hours. The local health authority then informs the regional authority.