Atlas of pathophysiology, 2 Edition

Part II - Disorders

Neurologic disorders

West Nile virus

West Nile is a virus transmitted by mosquitos that causes an illness that can range from mild to severe. Mild, flulike illness is commonly called West Nile fever. In its most severe form, West Nile virus can infect the central nervous system and cause meningitis, encephalitis, and death.


Spreads when a mosquito bites an infected bird and then bites a person

Risk factors for developing a severe form of the disease

·   Conditions that suppress the immune system, such as recent chemotherapy, recent organ transplantation, or human immunodeficiency virus

·   Pregnancy

·   Older age

The disease may also be spread through blood transfusions and organ transplantation. It's also possible for an infected mother to transmit the virus to her infant through breast milk.


West Nile virus is a type of organism called a flavivirus and is similar to many other mosquito-borne viruses. After infection, if encephalitis ensues, severe inflammation of the brain occurs. Intense lymphocytic infiltration of brain tissues and the leptomeninges causes cerebral edema, degeneration of the brain's ganglion cells, and diffuse nerve cell destruction.

Signs and symptoms

West Nile fever

·   Fever

·   Headache

·   Back pain

·   Muscle aches

·   Lack of appetite

·   Sore throat

·   Nausea and vomiting

·   Maculopapular or morbilliform rash on the neck

·   Abdominal pain

·   Diarrhea

Severe infection

·   Fever

·   Weakness

·   Stiff neck

·   Change in mental status

·   Loss of consciousness

In addition, a patient with encephalitis may have paresis or paralysis, cranial nerve deficits, sensory deficits, abnormal reflexes, seizures, and involuntary jerks.

Diagnostic test results

·   Serology reveals the presence of antibodies against West Nile virus in cerebrospinal fluid (CSF) or serum.

·   Complete blood count shows a normal or elevated white blood cell count (WBC).

·   Lumbar puncture and CSF testing show elevated WBC count (especially lymphocytes) and elevated protein level.

·   Magnetic resonance imaging of the head shows evidence of inflammation.


No specific treatment

Supportive treatment

·   I.V. fluids

·   Airway management

·   Respiratory support

·   Prevention of secondary infections

·   Analgesics




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