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St. Louis Encephalitis

Updated : February 27, 2024





Background

St Louis encephalitis is a virus spread from infected Culex mosquitoes to humans. It is a flavivirus, a positive-sense single-stranded RNA virus closely related to West Nile viruses, Powassan, and Japanese encephalitis.

The majority of instances occur in the summer and early fall in the central and eastern US. The majority of cases are either asymptomatic or manifest flu-like symptoms, including headaches, fatigue, nausea, body aches, and vomiting.

The majority of patients will heal spontaneously without developing encephalitis. Severe, invasive diseases that cause encephalitis are uncommon and more prevalent in elderly persons.

Following a flu-like prodrome, encephalitis or inflammation of the brain and meninges manifests as dizziness, agitation, disorientation, tremors, or coma. The fatality rate for encephalitis patients is between 5%-15%.

This illness has no specific treatment, and there is no evidence that antivirals treat symptoms. As there is no licensed vaccination, it can only be avoided by preventing mosquito bites.

Epidemiology

St. Louis encephalitis can be found from Argentina to Canada, and the vast majority of cases are detected in the US. In the Mississippi River valley and throughout the Gulf Coast, epidemics and periodic outbreaks have occurred, although occasional instances have been reported throughout the US, in Canada, the Caribbean, Central America, and Mexico.

In temperate regions, transmission occurs largely during late summer and early autumn, whereas in warmer climes, transmission occurs throughout the year. In 1975, about 2,000 cases of St. Louis encephalitis were reported, predominantly in the central states along the Ohio-Mississippi River basin.

Due to recurring epidemics, the number of reported cases fluctuates substantially each year. Most St. Louis encephalitis cases are asymptomatic, so it seems like this illness is underreported.

Anatomy

Pathophysiology

After St. Louis encephalitis has replicated in the area of the mosquito bite and the nearby lymph nodes, viremia develops. The infection usually lasts for 7 days. When the virus enters the brain, it can develop lymphocytic meningitis, which primarily affects grey matter.

Regions which are severely affected include basal ganglia, brainstems, the spinal cord, cerebral and cerebellar cortex and the hypothalamus. Rarely, this virus can affect white matter, resulting in acute demyelinating encephalomyelitis.

Etiology

The single-stranded RNA virus Flavivirus, which causes Saint Louis encephalitis, is spread by mosquitoes of the Culex genus. Culex pipiens, Culex quinquefasciatus, Culex tarsalis, and Culex nigripalpus are the most typical mosquito vectors.

Sparrows, pigeons, robins, and blue jays are among the involved species, which are found in both urban and rural habitats.

Humans and domesticated animals are dead-end hosts, meaning they can get the virus and develop symptoms, but cannot transmit it to other mosquitoes. This virus cannot be transmitted from human to human.

Genetics

Prognostic Factors

Most patients with St. Louis encephalitis are either asymptomatic or experience very mild flu-like symptoms. The fatality rate for Saint Louis encephalitis ranges between 5%-15%.

Age is a factor which drastically increases the risk of fatality. Individuals over the age of 60 have a 20% fatality rate, whereas it’s only 3%-6% for children and young adults.

In the first two weeks of infection, encephalitis is frequently the cause of death, although complications of hospitalization, such as pneumonia, account for the majority of deaths after two weeks. It is believed that once infected, the patient develops lifelong immunity against infection.

Clinical History

Physical Examination

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Medication

Media Gallary

References

https://www.ncbi.nlm.nih.gov/books/NBK470426/

St. Louis Encephalitis

Updated : February 27, 2024




St Louis encephalitis is a virus spread from infected Culex mosquitoes to humans. It is a flavivirus, a positive-sense single-stranded RNA virus closely related to West Nile viruses, Powassan, and Japanese encephalitis.

The majority of instances occur in the summer and early fall in the central and eastern US. The majority of cases are either asymptomatic or manifest flu-like symptoms, including headaches, fatigue, nausea, body aches, and vomiting.

The majority of patients will heal spontaneously without developing encephalitis. Severe, invasive diseases that cause encephalitis are uncommon and more prevalent in elderly persons.

Following a flu-like prodrome, encephalitis or inflammation of the brain and meninges manifests as dizziness, agitation, disorientation, tremors, or coma. The fatality rate for encephalitis patients is between 5%-15%.

This illness has no specific treatment, and there is no evidence that antivirals treat symptoms. As there is no licensed vaccination, it can only be avoided by preventing mosquito bites.

St. Louis encephalitis can be found from Argentina to Canada, and the vast majority of cases are detected in the US. In the Mississippi River valley and throughout the Gulf Coast, epidemics and periodic outbreaks have occurred, although occasional instances have been reported throughout the US, in Canada, the Caribbean, Central America, and Mexico.

In temperate regions, transmission occurs largely during late summer and early autumn, whereas in warmer climes, transmission occurs throughout the year. In 1975, about 2,000 cases of St. Louis encephalitis were reported, predominantly in the central states along the Ohio-Mississippi River basin.

Due to recurring epidemics, the number of reported cases fluctuates substantially each year. Most St. Louis encephalitis cases are asymptomatic, so it seems like this illness is underreported.

After St. Louis encephalitis has replicated in the area of the mosquito bite and the nearby lymph nodes, viremia develops. The infection usually lasts for 7 days. When the virus enters the brain, it can develop lymphocytic meningitis, which primarily affects grey matter.

Regions which are severely affected include basal ganglia, brainstems, the spinal cord, cerebral and cerebellar cortex and the hypothalamus. Rarely, this virus can affect white matter, resulting in acute demyelinating encephalomyelitis.

The single-stranded RNA virus Flavivirus, which causes Saint Louis encephalitis, is spread by mosquitoes of the Culex genus. Culex pipiens, Culex quinquefasciatus, Culex tarsalis, and Culex nigripalpus are the most typical mosquito vectors.

Sparrows, pigeons, robins, and blue jays are among the involved species, which are found in both urban and rural habitats.

Humans and domesticated animals are dead-end hosts, meaning they can get the virus and develop symptoms, but cannot transmit it to other mosquitoes. This virus cannot be transmitted from human to human.

Most patients with St. Louis encephalitis are either asymptomatic or experience very mild flu-like symptoms. The fatality rate for Saint Louis encephalitis ranges between 5%-15%.

Age is a factor which drastically increases the risk of fatality. Individuals over the age of 60 have a 20% fatality rate, whereas it’s only 3%-6% for children and young adults.

In the first two weeks of infection, encephalitis is frequently the cause of death, although complications of hospitalization, such as pneumonia, account for the majority of deaths after two weeks. It is believed that once infected, the patient develops lifelong immunity against infection.

https://www.ncbi.nlm.nih.gov/books/NBK470426/

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