The fact that we live in Poland does not mean that we will not get infected with diseases that come from distant countries. People travel constantly, so from time to time you hear about a greater concentration of the disease that comes from countries hundreds of kilometers away from us. One of them is West Nile Fever (West Nile Virus).
West Nile virus (WNV) is an RNA virus of the genus Flavivirus. The structure of this virus is similar to the tick-borne encephalitis virus found in Poland. West Nile fever in Europe first appeared in 1996, and the world’s first outbreak occurred in Uganda.
West Nile virus – how does it spread?
The first carriers of the virus are birds – migratory and tropical. Migratory birds transmit the virus to other countries. Mammals are hosts by chance, but some mammal species are more susceptible to infection than others, such as horses. In mammals, the virus “adheres” to the nervous system, therefore, after a short multiplication in cells, it penetrates the central nervous system. There, a cytopathic effect occurs (morphological changes and other anomalies that are the result of virus multiplication).
The transmitters are mainly mosquitoes, but also other blood-sucking insects, such as blackflies. The virus is transmitted to humans mainly by mosquitoes from the Culex family (common). Culex pipieus mosquitoes, which are very common in Europe, feed on the blood of both mammals and birds and are therefore the most dangerous carrier of the virus. Additionally, this mosquito can “survive” the virus throughout the winter.
Does West Nile Fever spread from person to person?
This phenomenon is very rare, but possible. There are known cases of infection in the world during organ transplantation, blood transfusion, from mother to child during breastfeeding, as well as laboratory workers who have studied material about a sick person.
West Nile virus – symptoms
Most human infections are asymptomatic. This is because the body detects the intruder and produces antibodies that destroy it quickly. Symptoms appear in about 20% of those infected, and in 10% the course of the disease is more severe and a doctor’s help is needed.
When symptoms are present, they are usually flu-like. They appear 3 to 14 days after being bitten by an infected insect. Mild symptoms include:
- muscle and joint pain;
- nausea and vomiting;
- enlarged lymph nodes;
- rash (abdomen, chest, back).
The mild course of the disease lasts 3-6 days and ends with recovery.
However, rarely, more severe symptoms may occur, mainly in the central nervous system. 1 in 150 infected people may have a more severe disease as a result of attacking the CNS. Half of these people may develop meningitis (symptoms – headache, nausea and vomiting, neck stiffness). Symptoms characteristic of inflammation of the brain or spinal cord can also be observed (dizziness, paralysis of the cranial nerves, dysphagia, speech problems, oliguria, urinary incontinence). Nervous system symptoms can also resemble Parkinson’s disease (trembling hands and muscles, muscle stiffness, masky face). Limb paresis may appear very rarely.
To sum up, a more severe course of the disease can also be manifested by:
- problems with speech and swallowing
- sight problems
In children it is mild and often asymptomatic. In some people with severe symptoms, remnants of symptoms may persist for life and, as a result, quality of life will be affected.
The mortality rate of people who required hospitalization is at the level of 2-14% and it occurs mainly in people with symptoms of encephalitis. The probability of mortality increases with age. In people over the age of 70 with symptoms of encephalitis, the mortality rate is 35%.
West Nile virus treatment
As it is a viral disease, there is no effective cure for it. In a mild course, we can treat ourselves as in the case of influenza by taking over-the-counter medicines with antipyretic, analgesic and anti-inflammatory effects (Aspirin, Ibuprofen, Paracetamol). It will certainly ease the symptoms and we will recover faster.
In severe course with symptoms of encephalitis and other serious symptoms, hospitalization is required. In the hospital, we will be given intravenous medications to reduce swelling.
Many therapies are under investigation and some of them show promise (interferon therapy).
Other treatments for encephalitis:
- intravenous administration of a polyclonal immunoglobin;
- corticosteroid therapy.
There is currently no vaccine for this disease. The only permitted vaccine is the veterinary vaccine for horses. However, work is underway.
It mainly consists in fighting mosquitoes through regular spraying. You can also protect yourself from mosquito bites by:
- wearing protective clothes with long sleeves and legs, especially during their peak activity (dawn and dusk);
- spraying the body with preparations against mosquitoes, black flies;
- installing mosquito nets in the windows;
- elimination of ponds in which mosquitoes can hatch;
West Nile virus in Poland
In Poland, the greatest probability of disease occurrence is in summer, in hot weather.
In the years 1995-1996 research was carried out on birds. They showed the occurrence of West Nile Virus antibodies in 2.8% of the examined house sparrows and 12.1% of mazurkas (Łomianki, Puszcza Kampinoska).
In 2005, WNV antibodies were also detected in a 55-year-old woman from the Białystok area after she saw a doctor after recurring fever, headaches and muscle aches. During hospitalization, she recovered (it was not severe).