Pathogens

Flaviviridae – Infection, Transmission & Diseases

Flaviviridae

Flaviviridae are viruses that are classified as RNA viruses because of their single-stranded RNA . The Flaviviridae family includes the genera Pestivirus , Flavivirus, and Hepacivirus.

Was sind Flaviviridae?

Flaviviridae belong to the group of single-stranded RNA viruses. They are often also referred to as flaviviruses, although the Flaviviridae also include the pestivirus and the hepacivirus in addition to the flaviviruses. All members of the Flaviviridae family are veiled. They are between 40 and 60 nm in size. In general, the Flaviviridae show low tenacity. The term tenacity comes from microbiology and describes the resistance of microorganisms to environmental influences. The viruses from the Flaviviridae group can be easily inactivated and thus rendered harmless using lipid solvents and disinfectants .

The Flaviviridae reproduce in the cell fluid of the host cell. They remain stable in a pH range between 7 and 9. In humans, the viruses can cause yellow fever , hepatitis C or tick-borne encephalitis (FSME), among other things.

Occurrence, Distribution & Properties

The flaviviruses from the Flaviviridae family are usually transmitted to birds or mammals by arthropods. For example, the TBE virus is transmitted by ticks . Dengue virus , Usutu virus , West Nile virus , yellow fever virus and Zika virus are transmitted by mosquitoes . Some of the viruses can also be transmitted through sexual intercourse or through infected blood products. In some cases, a diaplacental transmission of the virus from the infected mother to the unborn child is possible.

Most viruses of the Flavivirus genus are native to the African continent. But there are always infections with flaviviruses in South America or Asia. The TBE virus is an exception. The virus is widespread in endemic areas in Bavaria, Thuringia, Hesse, Rhineland-Palatinate and Baden-Württemberg.

The hepatitis C virus belongs to the hepacvirus genus and thus to the Flaviviridae family. Humans are the only natural host of the hepacivirus. Although great apes are also susceptible to infection, chronic infections such as those in humans are rather rare. The virus is spread worldwide. It is transmitted parenterally. Blood and blood products are the most common sources of infection. The virus is rarely transmitted sexually. Risk factors for infection with the hepacivirus are intravenous drug abuse, dialysis (especially dialysis performed before 1991), tattoos and piercings. In one third of the patients, however, the transmission route is unknown.

Diseases & Ailments

Viruses of the Flaviviridae family can cause a large number of viral infections in humans . Yellow fever is caused by infection with the yellow fever virus (Genus Flaviviridae). Yellow fever is one of the viral hemorrhagic fevers along with dengue fever. The disease proceeds in two phases. After six days of incubation , the first symptoms of the disease appear. These include fever , headache , chills , nausea , vomiting , muscle pain and yellowing of the skin. In some patients, symptoms resolve on their own after a few days. In others, the second phase of the disease develops, with a slow heart rate , fever, and a tendency to bleed . In this phase of the disease, the mortality rate is 50 percent. A causal treatment of yellow fever is currently not possible.

Dengue fever is also caused by a flavivirus. After an incubation period of about a week, those affected show flu-like symptoms. The notifiable infectious disease begins suddenly with a high fever, chills, headache, body aches , joint pains and nausea. After four to five days of illness, lymph node swelling and a skin rash develop . Initial infections with dengue fever often show a rather uncomplicated course. 90% of patients show only very mild or no symptoms at all. However, a second infection with the virus can cause hemorrhagic dengue feverdevelop. This is far more dangerous and can be fatal.

Tick-borne encephalitis is a disease that is caused by flaviviruses and can also be found in Germany. The TBE virus is transmitted by ticks. In the primary stage, those affected develop flu-like symptoms with body aches, headaches and a slightly elevated temperature . After the symptoms have subsided, there is a symptom-free phase. Around three weeks after infection, the secondary stage develops in 10 percent of all those infected. Tick-borne encephalitis at this stage can present as encephalitis , meningitis , or myelitis. Also the heart muscle , the liver and the jointscan be infected by the virus. TBE meningitis is accompanied by high fever and severe headaches. There may be meningism . If, in addition to meningitis, there is also encephalitis, patients have impaired consciousness , hyperkinesias and speech disorders . If the spinal cord is also involved , paralysis of the shoulders and upper extremities can occur. Bladder paralysis is also possible.

Hepatitis C, caused by the hepacivirus from the Flaviviridae family, usually takes a rather chronic course. Acute and symptomatic courses are expressed by exhaustion , flu-like symptoms and yellowing of the skin. However, more than 80 percent of all HCV infections are initially asymptomatic, but then tend to become chronic in the further course. Chronic hepatitis C leads to progressive destruction of the liver. 20 percent of all patients with chronic hepatitis C develop cirrhosis within 20 years . The risk of developing hepatocellular carcinoma is increased in cirrhotic patients. More than half of all liver cancersin Germany is due to an infection with the hepacivirus.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.