What is the Flavivirus?
Flaviviruses belong to the so-called Togaviridae and include many different species that can lead to different diseases. These include tick-borne encephalitis, Japanese encephalitis, ST Louis encephalitis, Murray-Valley encephalitis, as well as dengue fever and yellow fever. The flavivirus itself is not a single pathogen, but the term describes the genus of viruses responsible for different diseases in humans.
As is so common with many viruses, the genetic material of the pathogens is located in an outer envelope that has no organelles. The viruses do not have their own metabolism, so they are dependent on a host in whose biological processes they can intervene. In the case of flaviviruses, among others, human cells also serve as a suitable host. The virus is then transmitted by mosquitoes, ticks or similar insects.
What are the characteristics of the flavivirus?
On average, flaviviruses are about 50 nm in size and have a different looking spherical envelope depending on the species. For example, the yellow fever virus, also a flavivirus, has a diameter of only about 22-38 nm and is transmitted from one person to another with the help of mosquitoes and ticks. The flaviviruses enter the ticks or mosquitoes while they are sucking blood. If these subsequently bite or sting another person, the flaviviruses can also infect them. This happens, by the virus bringing its genetic material into the human cell, which in turn serves it as a host.
The viruses do not differ solely on the basis of their occurrence, but also on the basis of transmission. Tick-borne encephalitis is due to flaviviruses that enter humans through ticks in . St. Louise encephalitis, on the other hand, is transmitted by mosquitoes.
How widespread is the flavivirus and where does it predominantly occur?
In (South) East Asia, Japanese encephalitis, which is transmitted to humans by Culex mosquitoes from birds and pigs , is mainly prevalent. Mostly children in these countries contract encephalitis, which brings symptoms such as muscle and limb pain, high fever and chills. The mosquitoes are also mainly responsible for Murray Valley encephalitis. This rather rare form of encephalitis is more common in Australia , especially in the north of the country. The dengue virus, which triggers dengue fever, is also transmitted by mosquitoes . Above all, this flavivirus is widespread in Southeast Asia.
What diseases and complaints are triggered by the Flavivirus?
As already mentioned , flaviviruses are the cause of many different diseases. In the case of encephalitis, the brain is affected by an inflammation , which can become noticeable through various symptoms. The typical symptoms are:
- Fever,
- Cramps,
- Disturbances of consciousness,
- mental abnormalities.
In addition
, so-called neurological focal syndromes can occur, in which
functional systems are affected. The type of disorder
depends on which part of the brain is affected. An extension of the
encephalitis to the meninges and the spinal cord is also possible.
Inflammation of the roots of the spinal nerves is less common. In
some cases, the inflammations lead to irreversible damage
or death of the patient.
Yellow fever is also caused by infection with flaviviruses. The typical clinical picture is the combination of jaundice and fever episodes. As a rule, the fever occurs in episodes. Furthermore, the following symptoms may occur:
- Circulatory disorders,
- Liver disorders,
- Kidney disorders,
- Bleeding.
The
Dengue fever, which is also triggered by flaviviruses, is
like yellow fever a tropical and subtropical disease. In addition to the
fever, the following symptoms usually occur:
- Muscle pain,
- Joint pain,
- Headaches,
- Swelling of the lymph nodes
- Skin rash.
How is the flavivirus diagnosed?
Based on a detailed medical history, a doctor can already find the first indications of an infection with the flavivirus. The patient may have been in a high-risk area in the past few days. However, no definite diagnosis can be made on the basis of unspecific symptoms and a medical history. For this, a blood sample must be taken.
Unlike many other viruses, an infection with the flavivirus is confirmed by the detection of specific IgM antibodies in the serum and IgM antibodies in the cerebrospinal fluid. The detection of IgM antibodies in the CSF has greater specificity and greater sensitivity for flaviviruses.
How is flavivirus treated?
So far, there is no causal therapy against flavivirus. Therefore, the diseases are treated purely symptomatically. It is essential to drink enough fluids so that the high fever does not lead to dehydration. Rest and recuperation are also important. To relieve pain and reduce fever, it is recommended to take ibuprofen or paracetamol. If you have a fever, cool calf compresses can also help to bring the temperature down. In case of nausea and vomiting , only light food should be eaten.
If the patient's general condition deteriorates, intensive medical care in hospital may be necessary.
How can the flavivirus be prevented?
The safest and most effective measures to prevent flavivirus are as follows:
- Wear long trousers and long-sleeved clothing.
- Use mosquito nets,
- use sufficient insect repellent,
- Avoid or eliminate water points.
Is there an obligation to report the flavivirus?
According to Infektionsschutzgesetz, suspected illness, illness and also death from virus-related haemorrhagic fever as well as direct or indirect evidence of flaviviruses must be reported by name to the public health department . These reports must be submitted no later than 24 hours after the detection.