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West Nile Fever: Symptoms, Causes And Treatment

A viral infection, West Nile fever is spread by mosquitoes. The West Nile virus (WNV) is the cause of the fever and can result in neurological diseases and even death, in severe cases [1] . A recent news article has reported the spread of the West Nile virus, resulting in the death of a 7-year-old boy from Kerala's Malappuram region. Officials have issued a high safety alert in the districts of Mysore, Chamrajnagar, Kodagu and Dakshina Kannada in Karnataka, due to the close proximity of the states [2] .

In most cases, the virus does not cause the development of any symptoms. That is, about 80 per cent of the people who have WNV in their systems will not show any signs and the remaining 20 per cent can develop a fever, vomiting, headache or rashes. In the 20 per cent, about 1 per cent can face severe symptoms such as encephalitis or meningitis, along with life-threatening symptoms such as inflammation of the spinal cord or brain [3] .

As aforementioned, the disease is commonly spread through the bite of an infected mosquito (Culex pipiens) and develops during the summer season (mosquito season). The mosquitoes are commonly referred to as house mosquitoes [4] . The mosquitoes get infected when they feed on the infected birds. The virus is circulated into the salivary glands of the mosquitoes, which is then transported to our bloodstream where it multiplies and causes illness.

However, not everyone who gets a bite from the infected mosquito will contract the disease. It can be severe in people aged over 60 as well as for individuals with a weak immune system. It is not contagious and cannot be transmitted from person to other [5] .

Symptoms Of West Nile Fever

Eight out of ten people will develop no signs of the infection. The symptoms of West Nile fever usually develop from 1 to 14 days after one becomes infected.

In the case of mild infection, the signs and symptoms will as mentioned below. This is found in 20 per cent of the people infected by the virus [6] .

  • Fever
  • Headache
  • Body aches
  • Vomiting
  • Diarrhoea
  • Fatigue
  • Skin rash
  • Nausea
  • Swollen lymph glands

About 1 per cent of the individuals with the virus can develop a serious neurological infection, including inflammation of the brain (encephalitis) and of the membranes surrounding the brain and spinal cord (meningitis). The severe infection can last for a few weeks or even months and some of the neurological (muscle weakness) can become permanent [7] , [8] .

The symptoms include the following:

  • Headache
  • High fever
  • Neck stiffness
  • Stupor
  • Disorientation
  • Coma
  • Tremors
  • Loss of vision
  • Convulsions
  • Muscle weakness
  • Paralysis

The incubation period for West Nile fever is usually 3 to 14 days.

When To See A Doctor

Most of the symptoms of the infection subside by itself. For the symptoms such as severe headaches, a stiff neck, disorientation or confusion - you must get immediate medical care.

Causes Of West Nile Fever

The disease is caused by the West Nile virus. The virus spreads to humans and animals via the infected mosquitoes. The mosquitoes get infected when they feed on infected birds [9] .

However, some rare cases have been reported where the infection had spread through blood transfusions, organ transplants and breastfeeding. It may also transfer during pregnancy, that is, the virus spreads from the mother to child during pregnancy or breastfeeding [10] .

Risk Factors Of Nile Fever

One of the major factors affecting the development of symptoms from a West Nile infection is age. With age, the risk increases, especially if the individual is aged above 60 years.

Some of the other risk factors of the disease are as follows: [11]

  • Impaired immune system
  • Kidney conditions
  • Hypertension
  • Diabetes
  • Cancer

The possible complications that could arise from the infection are brain damage, permanent muscle weakness (sometimes similar to polio) and death.

Diagnosis Of West Nile Fever

Initially, the doctor will conduct a physical examination to check the symptoms, especially the external ones. This will aid the doctor in understanding whether you have genetic material or antibodies present in your blood, so as to combat the West Nile virus [12] .

The doctor will conduct the following tests to determine the type and seriousness of the fever [13] .

Lumbar puncture or spinal tap: This is carried out to examine whether the individual has meningitis. The doctor will analyse the cerebrospinal fluid surrounding your brain and spinal cord. A spinal tap is carried out by inserting a needle between the lower vertebrae of your spine, and a sample of fluid will be collected for laboratory analysis.

Blood tests: A blood test will help in understanding the rising level of antibodies, which attack foreign substances, such as viruses. If there is a rise in the count of antibodies, then the doctor will be able to understand the presence of an infection.

Brain tests: Tests such as electroencephalography (EEG) will be carried out to measure the brain's activity [14] . An MRI scan may also be conducted, in order to detect any inflammations in your brain.

Treatments For West Nile Fever

As the condition or the fever is caused as a result of viral infection, it does not have any specific treatment or cure. For mild cases, over-the-counter pain relievers can help symptoms such as ease mild headaches and muscle aches. You can use ibuprofen or aspirin. However, it is best not to give aspirin to children or teenagers. Teenagers and children who are recovering from flu-like symptoms or chicken pox should not be given aspirin [15] .

In severe cases, doctors recommend interferon therapy which is still being studied on. It is a type of immune cell therapy. Some of the other treatments include polyclonal immunoglobulin intravenous (IGIV), WNV recombinant humanized monoclonal antibody (MGAWN1) and corticosteroids [16] , [17] .

Prevention Of West Nile Fever

Although not curable, you can control the onset of the disease and prevent the symptoms. As mosquito bites are the primary and most common cause of West Nile fever, you can adopt the following measures while going outdoors, as well as while staying inside [18] .

  • Wear an insect repellent.
  • Make sure your home windows and doors have screens to stop mosquito from entering.
  • Keep your skin covered with long-sleeve shirts, pants, and socks.
  • Eliminate any standing water around your home, as it can turn into a breeding spot for mosquitoes.
  • Use mosquito netting around playpens or strollers, to protect your children from mosquito bites.

The other ways are by reducing the risk of animal-to-human transmission. Wear gloves and other protective clothing while handling sick animals or their tissues, and during slaughtering and culling procedures [19] , [20] .

View Article References
  1. [1] Hubálek, Z., & Halouzka, J. (1999). West Nile fever--a reemerging mosquito-borne viral disease in Europe.Emerging infectious diseases,5(5), 643.
  2. [2] Staff. (2019, Mar 21). West Nile Fever: K’taka Health Dept issues alert for border districts. The News Minute. Retrieved from
  3. [3] Chowers, M. Y., Lang, R., Nassar, F., Ben-David, D., Giladi, M., Rubinshtein, E., ... & Pick, N. (2001). Clinical characteristics of the West Nile fever outbreak, Israel, 2000.Emerging infectious diseases,7(4), 675.
  4. [4] Weinberger, M., Pitlik, S. D., Gandacu, D., Lang, R., Nassar, F., David, D. B., ... & Siegman-Igra, Y. (2001). West Nile fever outbreak, Israel, 2000: epidemiologic aspects.Emerging Infectious Diseases,7(4), 686.
  5. [5] Watson, J. T., Pertel, P. E., Jones, R. C., Siston, A. M., Paul, W. S., Austin, C. C., & Gerber, S. I. (2004). Clinical characteristics and functional outcomes of West Nile fever.Annals of Internal Medicine,141(5), 360-365.
  6. [6] Petersen, L. R., & Marfin, A. A. (2002). West Nile virus: a primer for the clinician.Annals of internal medicine,137(3), 173-179.
  7. [7] Glass, W. G., McDermott, D. H., Lim, J. K., Lekhong, S., Yu, S. F., Frank, W. A., ... & Murphy, P. M. (2006). CCR5 deficiency increases risk of symptomatic West Nile virus infection.Journal of Experimental Medicine,203(1), 35-40.
  8. [8] McKenna, M., Ronca, S. E., Nolan, M. S., & Murray, K. O. (2018). West Nile Encephalitis. InMeningitis and Encephalitis(pp. 107-124). Springer, Cham.
  9. [9] Hasebe, F. (2016). West Nile fever/Neuroinvasive disease caused by WNV.Nihon rinsho. Japanese journal of clinical medicine,74(12), 2030-2035.
  10. [10] Pletnev, A. G., Putnak, J. R., Chanock, R. M., Murphy, B. R., Whitehead, S. S., & Blaney, J. E. (2018).U.S. Patent Application No. 16/025,624.
  11. [11] Montgomery, R. R., & Murray, K. O. (2015). Risk factors for West Nile virus infection and disease in populations and individuals.Expert review of anti-infective therapy,13(3), 317-325.
  12. [12] Beck, C., Lowenski, S., Durand, B., Bahuon, C., Zientara, S., & Lecollinet, S. (2017). Improved reliability of serological tools for the diagnosis of West Nile fever in horses within Europe.PLoS neglected tropical diseases,11(9), e0005936.
  13. [13] Wollants, E., Smolders, D., Naesens, R., Bruynseels, P., Lagrou, K., Matthijnssens, J., & Van Ranst, M. (2018). Use of Next-Generation Sequencing for Diagnosis of West Nile Virus Infection in Patient Returning to Belgium from Hungary.Emerging infectious diseases,24(12), 2380.
  14. [14] Lustig, Y., Mannasse, B., Koren, R., Katz-Likvornik, S., Hindiyeh, M., Mandelboim, M., ... & Mendelson, E. (2016). Superiority of West Nile Virus RNA detection in whole blood for diagnosis of acute infection.Journal of clinical microbiology,54(9), 2294-2297.
  15. [15] Herring, R., Desai, N., Parnes, M., & Jarjour, I. (2018). Pediatric West Nile Virus-Associated Neuroinvasive Disease: A Review of the Literature.Pediatric neurology.
  16. [16] Razonable, R. R. (2016, September). Not the usual viral suspects: parvovirus B19, West Nile virus, and human T-cell lymphotrophic virus infections after kidney transplantation. InSeminars in nephrology(Vol. 36, No. 5, pp. 428-434). WB Saunders.
  17. [17] Bell, T., Espina, V., Lundberg, L., Pinkham, C., Brahms, A., Carey, B., ... & Liotta, L. (2018). Combination kinase inhibitor treatment suppresses Rift Valley fever virus replication.Viruses,10(4), 191.
  18. [18] Rasmussen, S. A., Meaney‐Delman, D. M., Petersen, L. R., & Jamieson, D. J. (2017). Studying the effects of emerging infections on the fetus: Experience with West Nile and Zika viruses.Birth defects research,109(5), 363-371.
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