West Nile fever

West Nile fever, also known as West Nile virus disease, is an infection caused by the West Nile virus (WNV). It can result in a range of symptoms, from mild to severe.

Common Symptoms

• Fever
• Headache
• Tiredness and body aches
• Nausea and vomiting
• Rash (in some cases)

These symptoms are typically self-limiting and resolve on their own within a few days. However, in rare cases, the virus can cause more serious complications.

Rare but Serious Complications

• Encephalitis (inflammation of the brain)
• Meningitis (inflammation of the lining around the brain and spinal cord)

These severe symptoms are usually accompanied by neck stiffness, confusion, or seizures. In less than 1% of cases, West Nile virus can cause these serious complications.

Transmission

West Nile fever is transmitted to humans through the bite of an infected female mosquito. The mosquitoes get the virus when they bite an infected bird, such as a crow.

Prevention and Treatment

There are no vaccines available to prevent or medicines to treat West Nile fever. Rest, fluids, and pain medications may help relieve symptoms in mild cases. However, if you suspect you have been infected with West Nile virus, it is essential to consult with your healthcare provider for proper diagnosis and treatment.

References:

• [1] West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. (Source: Search result 4)
• [2] About 20% of people develop a fever, headache, vomiting, or a rash. (Source: Search result 4)
• [3] In less than 1% of people, encephalitis or meningitis occurs, with associated neck stiffness, confusion, or seizures. (Source: Search result 4)

Common Signs and Symptoms of West Nile Fever

West Nile fever, also known as West Nile virus infection, can cause a range of symptoms in people who contract the disease. While most people do not experience any symptoms, about 1 in 5 people may develop some flu-like symptoms.

• Fever: A high temperature is one of the most common symptoms of West Nile fever.
• Headache: Headaches are another frequent symptom, which can range from mild to severe.
• Body aches and pains: Many people experience muscle and body aches, similar to those experienced during a flu episode.
• Vomiting and diarrhea: Some individuals may also experience nausea, vomiting, and diarrhea.
• Rash: A skin rash is another possible symptom of West Nile fever.

These symptoms usually go away on their own within a few days to several weeks. However, in rare cases, the infection can progress to more severe forms of the disease, such as encephalitis or meningitis, which require immediate medical attention.

Prevalence and Duration

According to various sources [3][9], around 20 percent of infected people will show some fever symptoms, such as headaches, vomiting, and diarrhea. These symptoms usually pass quickly. Some symptoms, such as fatigue, can continue for up to several months after the initial infection.

It's essential to note that most people who contract West Nile virus do not experience any severe symptoms and recover fully [14][15]. However, some individuals may experience ongoing weakness and fatigue for months.

References:

• [3] - Around 20 percent of infected people will show some fever symptoms, such as headaches, vomiting, and diarrhea.
• [9] - These symptoms usually go away on their own within a few days to several weeks.
• [14] - West Nile virus (WNV) is a mosquito-borne illness that usually causes mild flu-like symptoms, such as a low-grade fever, headache, body aches, and fatigue.
• [15] - Most people infected with the West Nile virus do not experience any symptoms though some may develop a fever, headache, body aches, joint pains, vomiting and rash.

Diagnostic Tests for West Nile Fever

West Nile fever can be diagnosed through various tests, which are crucial in confirming the presence of the virus in a patient's body. Here are some of the diagnostic tests used to detect West Nile fever:

• Serology testing: This test detects the presence of antibodies against the West Nile virus in a patient's blood or cerebrospinal fluid (CSF). The IgM antibody is the preferred marker for diagnosing acute infection, while IgG antibody indicates past exposure [1][2].
• Enzyme-linked immunosorbent assay (ELISA): This test is used to detect the presence of West Nile virus-specific antibodies in a patient's blood or CSF. ELISA is considered the diagnostic test of choice for WNV infections [3].
• Plaque reduction neutralization test (PRNT): This test can distinguish serologic cross-reactions and is used to confirm the diagnosis of West Nile fever [4].
• PCR testing: Polymerase chain reaction (PCR) testing is a molecular test that detects the genetic material of the West Nile virus in a patient's blood or CSF. PCR testing is particularly useful for diagnosing WNV infections in patients who have not developed antibodies yet [5].

Timing and Type of Tests

The type of tests used to diagnose West Nile fever depends on the species of the test subject, with whole blood (EDTA) being the preferred sample for anti-coagulant [6]. The timing of testing also varies, with IgM antibodies typically appearing 3-8 days after illness onset and persisting for up to 90 days [7].

References

[1] Gubler D. J. West Nile encephalitis: An emerging disease in the United States. Clin Infect Dis. 2001;33:1713–1719.

[2] Mar 2, 2022 — What does the test measure? · Enzyme-linked immunosorbent assay (MAC-ELISA): MAC-ELISA is the preferred method of diagnostic testing for WNV.

[3] by WN Virus — Diagnosis and Tests​​ A provider can test your blood or cerebrospinal fluid (CSF) to look for antibodies or other signs of a West Nile virus infection. They ...

[4] Oct 3, 2017 — Diagnosis. West Nile virus can be diagnosed by a number of different tests: IgG antibody sero-conversion (or significant increase in antibody ...

[5] Patients with suspected West Nile virus (WNV) disease should first be tested for WNV-specific immunoglobulin (Ig)M antibodies in serum and/or cerebrospinal fluid (CSF).

[6] The type of tests and timing of the sampling for diagnosing WNV infections depends on the species of the test subject: Whole blood – EDTA preferred (DO NOT use heparin for anti-coagulant as heparin is inhibitory in PCR assays).

[7] This test should be used for diagnostic purposes only. Profile Information. ... It is estimated that about 20% of those who become infected will develop West Nile fever with mild symptoms, including fever, headache, myalgia, and occasionally a skin rash on the trunk of the body. Case fatality rates among patients hospitalized during recent ...

Differential Diagnosis of West Nile Fever

West Nile fever, caused by the West Nile virus (WNV), can be challenging to diagnose due to its similarity in symptoms with other viral infections. The differential diagnosis for West Nile fever includes:

• Other viral infections: Such as dengue fever, Zika virus, and chikungunya [13]
• Herpes simplex virus type 1 (HSV-1) encephalitis: A serious condition that can present with similar symptoms to West Nile encephalitis [3]
• Viral meningitis: Inflammation of the lining around the brain and spinal cord, which can be caused by various viruses [5]
• Miliaria: A skin condition characterized by small, itchy bumps, which can be mistaken for West Nile fever [1]
• Cutaneous larva migrans: A skin infection caused by a parasitic worm, which can present with similar symptoms to West Nile fever [1]

Investigation and Testing

To confirm the diagnosis of West Nile fever, patients should undergo testing for WNV-specific immunoglobulin (Ig)M antibodies in serum and/or cerebrospinal fluid (CSF). In some cases, positive IgM results may need to be confirmed by neutralizing antibody testing at a state public health laboratory or CDC [11].

Prevalence of West Nile Fever

Approximately 25% of those infected with WNV develop WN fever, while 1 out of 150 to 250 develop neuroinvasive disease. Increasing viral load and female gender may increase the risk of developing WN fever [12].