West Nile fever

West Nile Fever: description

West Nile Fever is an infectious disease caused by the West Nile virus. It is endemic to Africa, India, Israel, Turkey and North America. Endemic area refers to a region in which a pathogen occurs permanently and can not be removed. Again and again, the virus causes epidemic outbreaks, in which the disease is very common.

Danger of infection in Germany

Update from 4.11.2019: In Germany, West Nile fever is (still) rare. So far, only returning tourists had brought the virus. In the summer of 2019, for the first time a case was known in which a patient had been infected directly in Germany by a mosquito bite and contracted an encephalitis. Experts expect much more cases in the future. In the south of Europe there are already long outbreaks of tropical fever. As the summer temperatures rise in Germany, the virus disease will also occur more frequently here – because at high heat, the pathogens multiply faster. Exact numbers do not exist, as many infections go unnoticed.

West Nile fever: symptoms

West Nile fever remains symptomless in almost 80 percent of cases. Physicians also speak of a clinically silent infection. About 20 percent of patients have sudden onset but mild symptoms. These are similar to a flu.

West Nile fever begins after an incubation period of 2 to 14 days. This is the time between infection with the pathogens and the onset of West Nile virus symptoms. This includes:

• fever
• chills
• Fatigue, malaise
• a headache
• back pain
• nausea
• Vomit
• lymphadenopathy

About half of the patients who have West Nile Virus symptoms have a so-called maculopapular rash on the trunk. This is what doctors call a gnarled, spotty rash. The complaints last on average for three to six days.

West Nile Fever: Severe courses

Less than one percent of patients who have been infected with West Nile virus are experiencing severe disease. These patients develop encephalitis or meningitis. It is noticeable with the following symptoms:

• very high fever
• a headache
• stiff neck
• Disturbances of consciousness
• paralysis
• epileptic seizures (convulsions)
• Vision and hearing disorders

Patients with severe West Nile fever may fall into a coma and die. The symptoms can last for weeks or even last forever. In rare cases, the heart or liver are also affected.

West Nile Fever: Causes and Risk Factors

The causative agent of West Nile Fever is the West Nile Virus (WNV). It belongs to the Flaviviren and consists of the genome (RNA) and a shell in which various proteins (proteins) are incorporated.

The WNV is transmitted by mosquitoes to humans. The genus of mosquitoes, which most often transmits the West Nile Fever, is called Culex and also occurs in Germany. Other mosquito species such as Aedes or Mansonia can transmit the West Nile virus to humans.

As a reservoir for the West Nile Fever serve birds. But even horses and cats can be infected. If a mosquito stings one of these animals, it picks up the viruses on its trunk. If she subsequently stings a human, she can transmit the West Nile virus to her.

In rare cases, the pathogens of West Nile fever can also be transmitted by blood transfusions, organ transplants. During pregnancy and lactation, the mother can transmit the virus to the fetus or infant.

West Nile Fever: Examinations and Diagnosis

If you feel chipped off during or after a trip to endemic areas and get a high fever, see a doctor. It is not easy to diagnose West Nile fever as there are many diseases with similar symptoms. In the preliminary discussion, your doctor will ask you the following questions:

• Since when do you feel sick?
• How high is your fever?
• What symptoms do you have besides?
• Have you been abroad recently, for example in Africa?
• Have you noticed an insect bite?
• Do people around you have similar symptoms?

West Nile fever: physical examination

Subsequently, your doctor will examine you physically. First, he inspects your skin. He pays attention to possible insect bites or a suspicious rash. He also scans your lymph nodes for swelling. He listens to lungs, heart and abdomen and checks whether you suffer from neck stiffness. For that he leans your head forward on the chest. In addition, it checks the function of your cranial nerves by testing your vision and hearing as well as the movement of your facial muscles and tongue. Finally, he tests the muscle power of your arms and legs, which you are to move against resistance, as well as your reflexes.

West Nile Fever: Laboratory Diagnostics

The diagnosis of West Nile Fever can only be clearly made by laboratory chemistry. For this either blood or nerve water (cerebrospinal fluid) is needed. Liquor is obtained by means of a lumbar puncture, in which a needle is carefully advanced between the vertebral bodies into the spinal canal.

The blood or CSF sample will be tested in the laboratory either for antibodies to the West Nile virus or to the genome (RNA) of WNV. The so-called ELISA test, which is used to detect antibodies to the West Nile virus in the patient’s blood, can also be falsely positive. This is because there are many similar flaviviruses, such as the causative agents of tick-borne encephalitis (TBE) or yellow fever. Therefore, after a positive ELISA test, a confirmatory test is performed to make sure that they are antibodies that specifically target the WNV.

In the first few days after the infection, the genome of the West Nile virus can also be detected in the blood or cerebrospinal fluid. For this purpose, a so-called polymerase chain reaction (PCR) is used in the laboratory.

West Nile fever: similar diseases

The diagnosis of West Nile Fever is not easy for your doctor. This is because the symptoms of West Nile virus can also be similar in many other diseases. These include:

• Flu (influenza)
• Dengue fever
• malaria
• chikungunya
• yellow fever
• TBE

West Nile fever: treatment

West Nile fever is treated symptomatically. This means that the individual complaints that the patients have are treated. The cause itself, in this case the West Nile virus, can not be treated, because there is no drug for this virus yet. Also antibiotics do not help, because they only act against bacteria, but not against viruses.

The fever is most effectively treated with antipyretic drugs such as ibuprofen or acetaminophen. In addition, calf rolls help to reduce the fever. Relax and give your body time to recover. You should also drink a lot to prevent dehydration.

If you feel sick or need vomiting, you can take medicines that suppress the nausea. These include, for example, dimenhydrinate. You should also eat light food such as rusks or broth.

If you have a severe case of West Nile Fever, your GP will send you to a hospital. There, the therapy can be intensified, for example by the administration of fluid via the vein (infusion).

West Nile Fever: Prevent

To prevent illness of West Nile fever, you should protect against mosquito bites in risk areas. The following helps:

• Wear long clothes!
• Sleep under a mosquito net!
• Provide doors and windows with fly screens!
• Spray yourself and your clothes with repellents (anti-mosquito sprays)!

A vaccine against West Nile fever currently exists only for horses.

West Nile fever: disease course and prognosis

The West Nile fever usually has a good prognosis, especially in children. People over the age of 50 are more likely to develop severe West Nile fever. The same applies to patients with diabetes mellitus or immunodeficiency.

About half of the patients suffering from encephalitis retain long-term consequences. These manifest in neurological damage such as paralysis or visual disturbances. The West Nile feverEncephalitis is fatal in 15 to 40 percent of cases.