West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family Flaviviridae, specifically from the genus Flavivirus, which also contains the Zika virus, dengue virus, and yellow fever virus.

West Nile Virus (WNV) can cause neurological disease and death in people. WNV is commonly found in Africa, Europe, the Middle East, North America and West Asia.

Spread of the disease:

West Nile virus is primarily transmitted by mosquitoes, mostly species of the genus Culex. Mosquitoes become infected when they feed on infected birds, which circulate the virus in their blood. The virus eventually gets into the mosquito’s salivary glands. During later blood meals (when mosquitoes bite), the virus may be injected into humans and animals, where it can multiply and possibly cause illness.

The primary hosts of WNV are birds, so that the virus remains within a “bird–mosquito–bird” transmission cycle.

Horses, just like humans, are “dead-end” hosts, meaning that while they become infected, they do not spread the infection. Symptomatic infections in horses are also rare and generally mild, but can cause neurologic disease, including fatal encephalomyelitis.

Symptoms:

No symptoms in most people. Most people  (8 out of 10) infected with West Nile virus do not develop any symptoms.

Febrile illness (fever) in some people. About 1 in 5 people who are infected develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.

Serious symptoms in a few people. About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord).

Severe illness can occur in people of any age; however, people over 60 years of age are at greater risk. People with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and people who have received organ transplants, are also at greater risk.

Recovery from severe illness might take several weeks or months. Some effects to the central nervous system might be permanent.

About 1 out of 10 people who develop severe illness affecting the central nervous system die.

Diagnosis

If one develops any of the symptoms mentioned above, he or she must consult a healthcare provider. The healthcare provider will carry out tests to identify the infection. These tests are:

  • IgG antibody sero-conversion in two serial specimen collected at a one week interval by enzyme-linked immunosorbent assay (ELISA)
  • IgM antibody capture enzyme-linked immunosorbent assay (ELISA)
  • Neutralisation assays
  • Viral detection by reverse transcription polymerase chain reaction (RT-PCR) assay
  • Virus isolation by cell culture.

Treatment:

  • No vaccine or specific antiviral treatments for West Nile virus infection are available.
  • Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms
  • In severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.

 

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