What is the paramyxovirus?

Paramyxoviruses are a family of enveloped, single-stranded RNA viruses. They cause mainly respiratory diseases in many animals as well as in humans, but are also pathogens for severe systemic diseases. The virions have an average size of about 150-250 nm, are oval and surrounded by a capsid. The genome consists of a single-stranded RNA with negative polarity.

What are the properties of the paramyxovirus?

Thanks to the envelope, the virus can not only enter the host cell very quickly, but also leave it easily. Unlike other enveloped viruses, paramyxoviruses have a surface that can adapt to changing conditions, this gives them an enormous evolutionary advantage.

The viral envelope has a major influence on the effectiveness of disinfection measures. The lipid content of the envelope makes the viruses vulnerable to disinfectants that have a fat-solubilising effect such as agents based on alcohols and detergents. These disinfectants are called "limited virucidal".

What diseases are caused by the paramyxovirus?

The paramyxovirus most familiar to humans, is probably the measles virus. Analyses of genetic material have shown that it differentiated from the pathogen of the so-called rinderpest as early as the 6th century BC and then specialised in humans. Large cities in ancient times developed and living of many people in a confined space accelerated the spread of the virus at that time.

Today, the paramyxovirus, or measles virus, is a problem especially in the developing countries. There, not only is there a lack of adequate health care, but also the money to vaccinate the population across the board. Every year, about ten million people worldwide contract the paramyxovirus and about 140,000 die from it. Most of them are children under the age of five. In the so-called industrialised nations, which includes Germany, outbreaks occur occasionally. Very often after measles parties. Here, the children of vaccination opponents infect each other with measles. According to the Robert Koch Institute, there were about 514 measles cases in Germany in 2019.

However, measles is by no means a harmless childhood disease that is triggered by paramyxoviruses . First, the viruses attack the immune cells and begin to multiply in them. The following generation then reaches the cells of the respiratory tract via the lymphatic tracts. The virions are released into the environment via mucus droplets when sneezing or coughing. The measles virus is the most infectious virus of all, because its reproduction number is between 12 and 18. This means that one infected person will infect between 12 and 18 other people.

What are the symptoms of paramyxovirus?

To stay with the best-known paramyxovirus, the measles virus, now the symptoms that most often occur during an infection. After an incubation period of one to two weeks, the disease begins with the catarrhal stage, which is characterised by the following symptoms :

• Fever,
• Rhinitis,
• Cough,
• Conjunctivitis.

Somewhat more characteristic is the development of a white-spotted exanthema at the oral mucosa. These spots are called Koplik spots. Between the second and fourth day, the typical measles rash appears. This starts behind the ears and on the face and lasts about seven to ten days. This stage is followed by the so-called transitory immunodeficiency. The paramyxoviruses leave massive damage in the immune system, which makes the patient more susceptible to all kinds of infections after the disease has subsided. It can even lead to a deletion of the entire immune memory, which lasts for several years.

The following secondary infections, which can leave permanent damage, are most feared:

• Measles croup,
• Meningoencephalitis,
• subacute sclerosing panencephalitis,
• Myocarditis.

How is paramyxovirus diagnosed?

Paramyxovirus is detected by an antibody test in the blood. A PCR test can also be used.

How is paramyxovirus treated?

So far, there are no drugs against paramyxovirus. This means that treatment is purely symptomatic:

• Paracetamol or ibuprofen can be taken in case of high fever and severe pain.
• Rest, rest and light food are advisable.
• Sufficient fluid intake is essential to prevent dehydration.

What other types of paramyxoviruses are there?

the other very well-known viruses of the paramyxovirus family include the mumps viruses. They are almost as old as the measles viruses, but cause a completely different form of the disease. Primarily an inflammation of the parotid gland develops, which can be accompanied by encephalitis. Every year, around 700 people are infected in Germany , mainly children. The mumps viruses, like the measles viruses, are transmitted from person to person via droplets.

the two fairly new paramyxoviruses are the Hendra virus, discovered in 1995, and the Nipah virus, discovered in 1999. Both belong to the genus of henipaviruses, which is a subspecies of the paramyxoviruses . Like the measles and mumps viruses, these viruses also attack the cells of the respiratory tract and are thus also transmissible through droplets . For the most part, the respiratory tract is spared from the viruses , in contrast to the cells of the central nervous system. In humans, these two types of paramyxoviruses cause severe encephalitis.

Henipaviruses are mainly found in South and Southeast Asia, North and East Australia, Madagascar and some West Pacific islands. The Nipah viruses are still mainly found in India, Bangladesh and Malaysia.

How can paramyxovirus be prevented?

Just two vaccination doses are enough to have lifelong protection against measles and mumps. This is because the virus hardly changes. Of the 24 genotypes identified so far, only very few are still active at all and are constantly epidemiologically recorded and monitored by the World Health Organisation (WHO), . In order to achieve herd immunity , at least 93 percent of the population must have been vaccinated.

So far, there is no vaccine protection against the Henipavirus and the Nipah virus . To date, these two types of paramyxovirus do not play a role in Germany, yet there is already a reporting obligation so that the spread of the viruses can be prevented. The Robert Koch Institute considers the Henipavirus as well as the Nipah virus to be pathogens of threatening transmissible diseases in the sense of the Infection Protection Act.