West Nile Virus: Symptoms & Therapy in West Nile Fever

More and more people in Europe suffer from the West Nile fever. Some of those affected even died from the disease. In Germany, the virus responsible for the disease was first detected in migratory birds. In the meantime, cases of sick people are becoming known repeatedly. We explain what is behind the West Nile virus and how fever symptoms manifest themselves in humans.

What is West Nile fever?

West Nile fever is an infectious disease caused by the West Nile virus. The virus belongs to the Flaviviriad family and can be found in tropical and temperate regions.

The virus mainly affects birds but can also be transmitted to humans and certain mammals such as horses. Infectious diseases are notifiable in both animals and humans.

 

Symptoms of West Nile Fever

About 80 per cent of all human cases develop no symptoms; the infection with the West Nile virus usually goes unnoticed.

In the remaining 20 per cent of cases, flu-like symptoms appear. The incubation period here is two to 14 days.

Symptoms caused by West Nile virus infection may include:

• sudden fever
• headache
• body aches
• lymph node swelling
• chills
• exhaustion
• pale, patchy rash radiating from the trunk

the course of the infectious disease

After the first flare-up of fever, the symptoms may initially weaken. After that, however, the fever increases again (biphasic course).

Towards the end of the fever phase, slightly less than half of those affected report a rash that lasts about a week. The disease usually heals on its own.

 

Complications of West Nile fever

West Nile fever can also be severe because the virus can cross the blood-brain barrier. This can cause encephalitis  ( inflammation of the brain), meningitis  (inflammation of the meninges), or paralysis  (acute signs of paralysis). These complications can result in permanent damage or even death.

Experts have found that the virus can also lead to kidney failure or affect other organs, such as the heart or liver.

Infection with the West Nile virus can have long-term effects even months after the symptoms have subsided. These include complaints such as tiredness, muscle pain or difficulty concentrating.

Who is mainly affected by a severe course?

Above all, people over 50 years of age, children and people with a weakened immune system, such as people with cancer or HIV, are at risk of West Nile fever taking a severe course.

The older the affected person is, the greater the risk of the infectious disease spreading to the brain and nervous system.

A severe course of the disease involving the brain or spinal cord (neuroinvasive course) occurs in about every hundredth affected person. 1 Mortality is then around five to ten per cent.

Diagnosis of West Nile fever

The disease can be detected by directly detecting the virus in the blood using a culture culture or virus genome detection (RT-PCR; reverse transcriptase-polymerase chain reaction). The latter is a unique test method for detecting viruses in the blood. This procedure is usually used a few days after the onset of symptoms.

If the disease has existed for a long time, the virus can be detected via antibodies in the blood serum or liquor.

Since the West Nile virus is very similar to other viruses of the same genus, there is often a risk of confusion, for example, with the dengue or yellow fever virus. A plaque reduction neutralization test (PRNT) is usually performed to rule out these diseases. The blood serum is examined for neutralizing antibodies.

 

West Nile fever: what to do?

There is no particular antiviral therapy for the virus. Therefore, West Nile fever treatment focuses on relieving the symptoms, for example, with antipyretics.

If the disease takes a severe course, hospital care is advisable to be able to counteract the complications quickly.

How is West Nile Virus transmitted?

Mosquitoes transmit the virus. So far, it has been found in over 43 species of mosquitoes, particularly in the Culex genus.

Most often, infected birds are the reservoir hosts. This means the birds are infected with the virus long-term but do not suffer symptoms. Reservoir hosts, therefore, represent a source of dangerous infections for humans and other mammals.

If a mosquito bites such birds, the virus is transmitted to the mosquito via the blood. Many mosquito species bite both birds and humans – an example is the Asian tiger mosquito, which has spread across Europe. The mosquito then spreads the virus further by biting a human or mammal.

West Nile virus can also be transmitted through direct blood contact. Accordingly, transmission from person to person cannot be ruled out, for example, in the case of a blood transfusion or an organ transplant.

In addition, infected mothers can transmit the virus to their children during pregnancy or later when breastfeeding.

Virus areas: where does West Nile fever occur?

The West Nile virus has so far been detected on five continents. It is geographically more widespread than any other virus transmitted via mosquitoes.

In Africa, West Nile fever is mainly observed in Uganda and Mozambique. However, the infectious disease has also spread to Egypt, India, Southeast Asia, and the Middle East.

The spread of the virus is also increasing in Europe. 2 Romania, Italy and Greece are particularly affected. Still, there are also registered cases in some Central European countries, such as Serbia and Hungary.

 

West Nile fever in Germany

In Germany, the West Nile virus was first detected in birds in Saxony-Anhalt in the summer of 2018. In September 2019, a person fell ill with West Nile fever and was infected by a mosquito in this country. Previously, the virus had only occurred in Germany as a travel sickness.

In September 2020, nine more cases were confirmed in Germany. These occurred in Saxony and Berlin. None of those affected had travelled, so the infection with West Nile fever must, in all probability, have occurred in Germany. Individual cases were also reported in 2023.

So far, almost all confirmed cases in Germany have occurred in Berlin, Brandenburg, Saxony or Saxony-Anhalt. A case was also reported from Bavaria. Researchers assume the West Nile virus will become more established in Germany in the coming years.