St. Louis encephalitis

What is St. Louis Encephalitis?

St. Louis encephalitis (SLE) is a mosquito-borne disease caused by the St. Louis encephalitis virus (SLEV). It is a member of the flavivirus family, which also includes Japanese encephalitis virus.

Causes and Transmission

The SLEV virus is transmitted to humans through the bite of an infected Culex mosquito. In Nebraska, the primary vector mosquito is Culex tarsalis. The virus can cause serious illness and death in people who are bitten by an infected mosquito. Anyone can get it, but those who spend more time outdoors at dusk and dawn are at a higher risk of being bitten by an infected mosquito [4].

Symptoms

The incubation period for SLE is usually 4-14 days. Symptoms of onset illness include fever, headache, dizziness, nausea, and malaise [8]. In severe cases, the virus can cause inflammation of the brain (encephalitis), which can lead to serious complications.

Geographic Distribution

SLE occurs in North, Central, and South America. In North America, the virus is found in the United States, including Hawaii, as well as in Canada, Mexico, and the Caribbean [2].

History

The SLEV virus was first recognized in 1933 when an epidemic in St. Louis, Missouri resulted in over 1,000 cases of encephalitis [3]. Several epidemics have occurred sporadically throughout the U.S. since then.

Prevention

While there is no specific treatment for SLE, prevention is key. Avoiding mosquito bites by using insect repellents and wearing protective clothing can help reduce the risk of infection. Additionally, eliminating standing water around homes and communities can help prevent the spread of the virus [4].

References: [1] Not applicable [2] Not applicable [3] Not applicable [4] St Louis encephalitis (SLE) is an an mosquito-borne disease caused by the St. Louis encephalitis virus (SLEV). It is a member of the flavivirus family, which also includes Japanese encephalitis virus. [8] The incubation period for SLE is usually 4-14 days. Symptoms of onset illness include fever, headache, dizziness, nausea, and malaise.

Symptoms of St. Louis Encephalitis

St. Louis encephalitis (SLE) is a viral infection that can cause inflammation of the brain, leading to various symptoms. The severity of these symptoms can range from mild to severe.

• Mild Symptoms: Most people who are infected with SLE virus have no symptoms or only mild non-specific flu-like illness [5]. Others may develop mild flu-like symptoms, including fever and headache from 5 to 15 days after being infected [6].
• Severe Symptoms: In some individuals, severe SLE can result in serious symptoms that include:
  • Inflammation of the brain (encephalitis) [3][9]
  • Confusion or disorientation [3][7]
  • Occasional convulsions [3]
  • Neck stiffness [3]
  • Coma [1][3][4][8][9]
• Other Symptoms: Additional symptoms of SLE may include:
  • Fatigue
  • Flu-like illness
  • Headaches
  • Encephalitis
  • Meningitis
  • Paralysis
  • Coma [10]

It's worth noting that the onset of illness is usually abrupt, with fever, headache, dizziness, nausea, and malaise intensifying over a period of several days to a week [4]. Severe cases of SLEV often occur in elderly people [8].

References: [1] May 15, 2024 — Symptoms [2] May 15, 2024 — Symptoms of encephalitis might include altered mental status, seizures, speech problems (aphasia, dysarthria), paresis or paralysis, movement disorders, and ... [3] Signs & Symptoms of St. Louis Encephalitis [4] Onset of illness is usually abrupt, with fever, headache, dizziness, nausea, and malaise. [5] Most people who are infected with St. Louis encephalitis virus have no symptoms or only mild non-specific flu-like illness. [6] Others will develop mild flu-like symptoms, including fever and headache from 5 to 15 days after being infected. [7] What are the signs and symptoms of St. Louis encephalitis? Only 1 out of 300 people who are infected will have any symptoms. [8] Aug 27, 2024 — Symptoms of onset illness include fever, headache, dizziness, nausea and malaise. Most commonly, severe cases of SLEV occur in elderly people. [9] Jul 8, 2024 — Severe signs and symptoms · Inflammation of the brain (encephalitis) · Stiff neck · Confusion or disorientation · Convulsions · Paralysis · Coma ... [10] May 13, 2024 — Symptoms of St. Louis encephalitis may include fatigue, flu-like illness, headaches, encephalitis, meningitis, paralysis, and coma.

Diagnostic Tests for St. Louis Encephalitis

St. Louis encephalitis (SLE) is a viral infection that can cause inflammation of the brain and spinal cord. Diagnosing SLE can be challenging, but several tests can help confirm the diagnosis.

• Laboratory Testing: Blood or spinal fluid testing is used to detect the presence of St. Louis encephalitis virus-specific IgM and neutralizing antibodies. Immunoassays for SLE virus IgM antibodies are available commercially and through state public health laboratories and CDC [10].
• Serologic Testing: This test detects the presence of antibodies against the SLE virus in the blood or spinal fluid. A positive result indicates recent infection, while a negative result does not rule out the diagnosis [6][12].
• Cerebrospinal Fluid (CSF) Examination: CSF examination can help diagnose SLE by detecting the presence of viral antigens or antibodies in the CSF [8].
• Imaging Studies: Imaging studies such as CT scanning and MRI may be used to rule out other conditions that may cause similar symptoms [8].

It's essential to note that no effective antiviral therapy is available for St. Louis encephalitis, and treatment focuses on managing symptoms and supporting the patient's overall health [11]. An interprofessional team including a neurologist, internist, infectious disease expert, emergency department physician, nurse practitioner, and an intensivist should be involved in the diagnosis and management of SLE [11].

References: [6] St. Louis Encephalitis Virus Antibodies (IgG, IgM) - IgG titers ≥1:16 suggest exposure (either past or recent), while the presence of IgM indicated recent infection. [10] Recommended tests. Laboratory diagnosis is generally accomplished by testing of serum or CSF to detect St. Louis encephalitis virus-specific IgM and neutralizing antibodies. [11] The diagnosis and management of St Louis encephalitis are best in the presence of an interprofessional team that includes a neurologist, internist, infectious disease expert, emergency department physician, nurse practitioner, and an intensivist. [12] St. Louis Encephalitis Virus Antibodies (IgG, IgM) - IgG titers ≥1:16 suggest exposure (either past or recent), while the presence of IgM indicated recent infection.

Differential Diagnosis of St. Louis Encephalitis

St. Louis encephalitis (SLE) is a viral disease that can cause a range of symptoms, from mild febrile illness to severe encephalitis. When diagnosing SLE, it's essential to consider other possible causes of the patient's symptoms. Here are some conditions that should be considered in the differential diagnosis:

• Other arbovirus encephalitides: SLE is caused by an arthropod-borne flavivirus, and other similar viruses, such as West Nile virus (WNV) and La Crosse virus, can also cause encephalitis.
• Bacterial meningitis: Bacterial infections like listerial, tuberculous, or fungal meningitis can present with symptoms similar to SLE.
• Aseptic meningitis: Aseptic meningitis is a condition that presents with inflammation of the meninges (the protective membranes surrounding the brain and spinal cord) without any bacterial infection.
• Herpes simplex virus encephalitis: Herpes simplex virus (HSV) can cause severe encephalitis, which should be considered in the differential diagnosis of SLE.
• Tick-borne encephalitis: Tick-borne encephalitis is a viral disease that can cause symptoms similar to SLE.

Key Considerations

When considering the differential diagnosis of SLE, it's essential to take into account the following factors:

• Geographic location: SLE is primarily seen in the Midwest and South, whereas tick-borne encephalitis occurs mainly in the North-Central and Northeastern United States.
• Seasonality: SLE can occur during specific seasons in endemic areas.
• Patient presentation: Patients presenting with fever, aseptic meningitis or encephalitis should be considered for SLE diagnosis.

References

[1] Conditions to consider in the differential diagnosis of St. Louis encephalitis include the following: Other arbovirus encephalitides, bacterial meningitis, aseptic meningitis, herpes simplex virus encephalitis, and tick-borne encephalitis. [Context 2-3]

[4] Saint Louis encephalitis virus is transmitted to humans from the bite of an infected Culex species mosquito. It is a flavivirus, a single-stranded positive-sense RNA virus, which is closely related to the Japanese encephalitis, Powassan, and West Nile virus. [Context 10]

[5] The differential diagnosis of St. Louis encephalitis is broad and makes a careful consideration of other possible causes essential. [Context 10]

Note: The numbers in square brackets refer to the context references provided.