Only 26% of the arbovirus infections have been found to be symptomatic. Infections with arbovirus are more likely to be symptomatic in the female gender and the highly viremic cases. Nevertheless, when present, the signs and symptoms in patients suffering from California encephalitis are similar to those present in other arbovirus-induced encephalitidis.

Initially, before encephalitis occurs, there is a prodromal phase of 1 to 4 days. In this phase, headache, fever, chills, malaise and other non-specific symptoms start appearing. Vomiting, abdominal pain and other symptoms of gastrointestinal upset are also often present.

Later on, as the virus reaches the central nervous symptoms, stiffness of the neck and neurological signs and symptoms start becoming apparent. There is a progressive clouding of consciousness. In up to 10 to 15% of the cases, coma and convulsions can also occur.

Adults usually do not suffer from California encephalitis. However, infection with La Crosse virus can cause subacute encephalomyelitis in rare cases [7].

• Fever

  We present the first reported case of California encephalitis in rural Alabama; the patient was a 7-year-old boy who came to us with fever and seizures in the summer of 1994. [ncbi.nlm.nih.gov]

  Paracetamol (Acetaminophen) is used for treating headache and fever. Anti-convulsant drugs such as phenytoin and diazepam are given to the patients in whom seizures occur. [symptoma.com]

  The mild form is characterized by headache, malaise, GI symptoms, and a fever that may reach 104° F. [medical-dictionary.thefreedictionary.com]

  The fever will respond somewhat to antipyretics, but resolution of the fever is usually by lysis over a period of several days. [notesread.com]

  Mosqutio types and their diseases ( Dengue Fever, West Nile virus,Eastern equine encephalitis, Venezuelan equine encephalitis, yellow fever, filariasis, Japanese encephalitis, Saint Louis encephalitis, Western equine encephalitis, La Crosse encephalitis [play.google.com]

• Fatigue

  Asymptomatic infections are not uncommon, but symptoms including fever, headache, fatigue, lethargy, and nausea and vomiting often manifest five to 15 days post infection. [neha.org]

  Symptoms for La Crosse encephalitis include fever, fatigue, headache and vomiting with nausea initially. Should the disease progress, LACV may cause an inflammation of the brain, which can result in seizures. [mosquitonix.com]

  LACV disease is usually characterized by fever (usually lasting 2-3 days), headache, nausea, vomiting, fatigue (tiredness), and lethargy (reduced activity or alertness). [cdc.gov]

  Symptoms of LACV may include: Fever Headache Nausea Vomiting Fatigue These symptoms are similar to symptoms of the flu and other common ailments, like a stomach bug, so it’s imperative to not “wait it out” if your child has these symptoms as well as mosquito [phlabs.com]

  […] indistinct lesion borders Substance abuse Tremor, headache, altered mental status Varies depending on type of substance: prior history, drug-seeking behavior, attention-seeking behavior, paranoia, sudden panic, anxiety, hallucinations Electrolyte disturbance Fatigue [wikidoc.org]

• Chills

  Mild cases usually show non-specific symptoms with fever lasting 2-3 days, chills, headache, and lethargy. Gastrointestinal (GI) manifestations are common, including anorexia, nausea, and vomiting. [infectiousdiseaseadvisor.com]

  In this phase, headache, fever, chills, malaise and other non-specific symptoms start appearing. Vomiting, abdominal pain and other symptoms of gastrointestinal upset are also often present. [symptoma.com]

  CE) is an acute arboviral infection caused by the La Crosse bunyavirus transmitted by an infected mosquito, usually observed in infants, children or adolescents (6 months to 16 years), and characterized by the onset of flulike symptoms such as fever, chills [orpha.net]

  An early symptoms phase of 1–4 days commonly precedes the onset of encephalitis, manifesting as fever, chills, nausea, vomiting, headache, lethargy and abdominal pain. [2] The encephalitis is characterized by fever, drowsiness, and lack of mental alertness [en.wikipedia.org]

• High Fever

  Severe infections are marked by a rapid onset, headache, high fever, confusion, tremors, seizures, paralysis, coma, or death. [health.ny.gov]

  Although death may occur suddenly, within a few hours, it may come only after several days’ progression of high fever, convulsions, coma, and respiratory difficulty that requires oxygen and a respirator. Upper respiratory signs are negligible. [notesread.com]

• Acutely Ill Patient

  No virus has yet been isolated from the blood of an acutely ill patient. Virus has been recovered from brain tissue of a fatal case, but most patients survive. The laboratory diagnosis is therefore serologic. [notesread.com]

• Vomiting

  Initially, there is fever, headache, vomiting and abdominal pain. Later, when the virus reaches the brain, there is stiffness of the neck and diminishing of consciousness. Seizures and coma also occur. [symptoma.com]

  The illness characteristically began abruptly with fever, lethargy, vomiting, and progressive encephalitic findings during the first two to four days and with recovery in seven to ten days. [jamanetwork.com]

  LAC encephalitis initially presents as a nonspecific summertime illness with fever, headache, nausea, vomiting and lethargy. [en.wikipedia.org]

  Headache, fever, and vomiting were the most common presenting symptoms, each occurring in 70% or more of patients. Seizures occurred in 46%, and disorientation in 42%. [pediatricneurologybriefs.com]

  The more severe form may be marked by a sudden onset of fever, vomiting, headaches, lethargy, and signs of neurological involvement such as loss of reflexes, disorientation, seizure, loss of consciousness, and flaccid paralysis. [medical-dictionary.thefreedictionary.com]

• Nausea

  LAC encephalitis initially presents as a nonspecific summertime illness with fever, headache, nausea, vomiting and lethargy. [en.wikipedia.org]

  These symptoms include fever, headache, nausea and vomiting. There may be neurologic symptoms such as confusion or loss of balance and in more severe cases, convulsions or coma may occur. [smokymountainnews.com]

  Mild illness may include headache, fever, nausea, vomiting and tiredness. Children with severe disease may progress to severe headache, nausea, stiff neck, muscle aches, drowsiness, disorientation, and seizures. [tn.gov]

  Asymptomatic infections are not uncommon, but symptoms including fever, headache, fatigue, lethargy, and nausea and vomiting often manifest five to 15 days post infection. [neha.org]

  Gastrointestinal (GI) manifestations are common, including anorexia, nausea, and vomiting. The neuro-invasive disease is characterized by neurological symptoms, such as seizures, tremors, and convulsions. [infectiousdiseaseadvisor.com]

• Hypertension

  Delivery Models Health Care Economics, Insurance, Payment Health Care Policy Health Care Quality Health Care Reform Health Care Safety Health Care Workforce Health Disparities Health Informatics Health Policy Hematology History of Medicine Humanities Hypertension [jamanetwork.com]

  Effect of mild hypothermia on uncontrollable intracranial hypertension after severe head injury. J Neurosurg 1993 ;79: 363 - 368 43. Irazuzta J, Pretzlaff R, Rowin ME, Kiefaber M, Kamdar T. [content.nejm.org]

• Photophobia

  […] must be differentiated from other diseases that cause fever, headache, seizures, and altered mental status, such as: [1] [5] [6] [7] [8] Disease Similarities Differentials Meningitis Classic triad of fever, nuchal rigidity, and altered mental status Photophobia [wikidoc.org]

  % Relative risk 95% CI Symptoms Fever 15 100 21 84 Undefined; chi square = 0.28 Headache 15 100 23 92 Undefined; chi square = 0.51 Vomiting 14 93 20 80 2.47 0.39, 15.46 Stiff neck 9 60 15 † 63 0.94 0.42, 2.10 Photophobia 11 73 12 48 2.03 0.78, 5.29 [academic.oup.com]

  In August 2006, a previously healthy woman aged 43 years in week 21 of her pregnancy was admitted to a West Virginia hospital after experiencing severe headaches, photophobia, stiff neck, fever, weakness, confusion, and a red papular rash. [cdc.gov]

  In general, a patient with encephalitis presents with diffuse or focal neurologic signs and symptoms, including an altered mental state and level of consciousness, behavioral or personality changes, nuchal rigidity, photophobia, and generalized or focal [hawaii.edu]

• Seizure

  Seizures and coma also occur. The treatment for California encephalitis is mainly supportive. [symptoma.com]

  Recurrent unprovoked seizures occur even after the illness has passed develops in 20% of patients, especially those who had seizures during the acute illness. [en.wikipedia.org]

  The median age was 23 years (0-92 years); 56% were male; 58% required admission to ICU; 42% had seizures, and 18% were comatose. [ahcmedia.com]

  Seizures were the presenting finding in 58 of the patients (46 percent). Of those with seizures, 14 (24 percent) had status epilepticus, and 36 (62 percent) had seizures with a focal component. [content.nejm.org]

• Headache

  Paracetamol (Acetaminophen) is used for treating headache and fever. Anti-convulsant drugs such as phenytoin and diazepam are given to the patients in whom seizures occur. [symptoma.com]

  The mild form is characterized by headache, malaise, GI symptoms, and a fever that may reach 104° F. [medical-dictionary.thefreedictionary.com]

  California encephalitis virus must be differentiated from other diseases that cause fever, headache, seizures, and altered mental status. [wikidoc.org]

  California encephalitis orthobunyavirus or California encephalitis virus was discovered in Kern County, California and causes encephalitis in humans. [1] Encephalitis is an acute inflammation of the brain that can cause minor symptoms, such as headaches [en.wikipedia.org]

  As primary complaints, the fever and headache are often attributed to some traumatic incident that the patient or parent remembers as having occurred within the previous few days. The fever and headache are frequently accompanied by vomiting. [notesread.com]

• Confusion

  There may be neurologic symptoms such as confusion or loss of balance and in more severe cases, convulsions or coma may occur. Children and the elderly are the most susceptible to the disease. www.epi.state.nc.us/epi/arbovirus . [smokymountainnews.com]

  The inflammation causes the brain to swell, which leads to changes in the person's neurologic condition, including mental confusion and seizures Neurocritical Care Program Meet a team of experts who focus on you and your condition. [stanfordhealthcare.org]

  In rural areas where the physician is called to see a feverish, confused, somnolent, convulsive, or comatose child, the condition is often diagnosed as “farm encephalitis.” [notesread.com]

  Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances All results must be correlated with clinical history and other data available [mayocliniclabs.com]

  It may also cause mental confusion, body aches and a fever. Those are similar to symptoms with other viruses, so it's best to get a diagnosis from a doctor. [news8000.com]

• Irritability

  Do not apply insect repellent to a child’s hands, eyes, mouth, cuts, or irritated skin. Adults: Spray insect repellent onto your hands and then apply to a child’s face. Tips for Everyone Always follow the product label instructions. [cdc.gov]

  Sedatives may be required in restless and irritable patients.Other manifestations of California encephalitis are also treated similarly. Bed rest is advised for the patient’s comfort and ease of recovery. [symptoma.com]

  Symptoms of the infection, which causes irritation of the brain, include headaches, fever, nausea, vomiting, drowsiness and disorientation. Severe cases my include seizures, coma or even death. [wvlt.tv]

  The virus, which occurs more frequently in children 16 and younger, irritates the brain; symptoms can include headache, fever, nausea, vomiting, drowsiness and dizziness, and in severe cases, seizures or coma. [eu.knoxnews.com]

  Sedatives may be needed for irritability or restlessness. Acetaminophen is used for fever and headache. Anticonvulsants are used to prevent seizures. [en.wikipedia.org]

• Rabies

  A82.9 Rabies, unspecified A83 Mosquito-borne viral encephalitis A83.0 Japanese encephalitis A83.1 Western equine encephalitis A83.2 Eastern equine encephalitis A83.3 St Louis encephalitis A83.4 Australian encephalitis A83.5 California encephalitis A83.6 [icd10data.com]

  Viral encephalitis may develop during or after infection with any of several viral illnesses including influenza, herpes simplex, measles, mumps, rubella, rabies, chickenpox, and arbovirus infection including West Nile virus. [webmd.com]

  Explain the methods for diagnosing encephalitis caused by herpes simplex virus, Epstein-Barr virus, West Nile virus, influenza, rabies, enterovirus, Bartonella henselae, and Mycoplasma pneumoniae. [pedsinreview.aappublications.org]

  The prognosis of any particular case of encephalitis is uncertain, with a few exceptions where a fatal outcome is the rule (e.g., rabies virus). [clinicaladvisor.com]

A number of investigations are helpful in diagnosing this disease.
Cerebrospinal fluid (CSF) examination: In most cases of viral encephalitis, it is possible to isolate the causal agent from the cerebrospinal fluid.

The La Crosse virus however, cannot be isolated from the cerebrospinal fluid. Still, a number of other changes in the cerebrospinal fluid can be evaluated in order to detect this disease. These include a mild elevation in the protein content with a normal glucose level. The white cell count is also raised with a predominance of lymphocytes or monocytes. In addition, the intracranial pressure will be only slightly raised [8].

Blood analysis

Blood tests do not show significant changes. There may only be a mild increase in the number of white blood cells. Other parameters are usually normal [8].
Antibody titers: A number of specific antibody titers are of importance in the diagnosis of California encephalitis. IgM antibodies against viral antigens can also be detected by Enzyme Linked Immunosorbent Assay (ELISA) [9].

Imaging

Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are usually not of any diagnostic importance. No significant changes are observed except in the most severe cases where some nonspecific enhancement is seen on CT.

Histologic studies

Upon examination under light microscope, biopsy specimen show perivascular infiltration with lymphocytes and plasma cells. Degeneration of nerve cells and areas of necrosis are also seen.

• Periodic Lateralized Epileptiform Discharges

  lateralizing epileptiform discharges in 8, and focal epileptiform discharges in 3. [content.nejm.org]

  lateralizing epileptiform discharges • SIADH = syndrome of inappropriate antidiuretic hormone • MRI = magnetic resonance imaging • CDC = Centers for Disease Control and Prevention • HIV = human immunodeficiency virus La Crosse virus is a mosquito-borne [pediatrics.aappublications.org]

  lateralized epileptiform discharges in La Crosse encephalitis, a worrisome subgroup: clinical presentation, electroencephalogram (EEG) patterns, and long-term neurologic outcome. ( 18160548 ) de Los Reyes E.C....O'Neal J. 2008 9 Economic and social impacts [malacards.org]

• Hyponatremia

  Hyponatremia is a common complication and a risk factor for seizures and clinical deterioration. [pediatricneurologybriefs.com]

  Hyponatremia and increasing body temperature may be related to clinical deterioration. Introduction La Crosse virus is the most pathogenic member of the California encephalitis serogroup. [content.nejm.org]

• Complement Fixing Antibody

  Precipitin antibodies were detected only in the 40 patients with CE, whereas hemagglutination-inhibiting, neutralizing, and complement-fixing antibodies were also found in persons without a history of CE. [ncbi.nlm.nih.gov]

Currently, no specific antiviral therapy is available against La Crosse virus. California encephalitis is therefore treated with supportive aims.

• The intracranial pressure is reduced by administration of agents such as mannitol.
• Corticosteroids may be useful in reducing the inflammation in the brain.
• Paracetamol (Acetaminophen) is used for treating headache and fever.
• Anti-convulsant drugs such as phenytoin and diazepam are given to the patients in whom seizures occur.
• Sedatives may be required in restless and irritable patients.
  Other manifestations of California encephalitis are also treated similarly.
• Bed rest is advised for the patient’s comfort and ease of recovery.

The prognosis of the patients suffering from California encephalitis is usually good. Mortality rates are extremely low (around 1%). The prognosis is poorer in younger children.

Most of the cases recover completely. A fraction of the cases may develop some speech disorders or epileptic seizures.

The arboviruses are a group of arthropod-borne viruses that cause general infection as well as encephalitis and hemorrhagic fever in humans.

California encephalitis is caused by an Arbovirus belonging to the Bunyaviridae family. It is a single stranded virus with a core of ribonucleic acid (RNA) and is called the La Crosse virus [3] [4].

The La Crosse virus is transmitted to the human host by the bite of a mosquito that is scientifically known as Aedes triseriatus [5]. It is commonly known as the eastern treehole mosquito and is commonly found in the eastern and Midwestern states of the United States [6].

California encephalitis is a very common cause of arbovirus-induced encephalitis in the United States. As many as 75 cases are reported each year [1].

It is influenced by a number of epidemiological factors that are listed below:

• Age of the patient: California encephalitis is primarily a disease of childhood, usually affecting children aged 6 months to 16 years. Increasing age reduces the likelihood of the disease. The peak incidence is among children aged 4 to 10 years [2].

• Gender of the patient: California encephalitis is much more common in males as compared to females. This is probably because males tend to spend more time outdoors where they can receive the disease agent from mosquitoes.

• Geographical location: It is most common in the Midwestern states of the United States.

• Season: Most cases of California encephalitis occur during the late summer to early fall.

The La Crosse virus enters the human body by the bite of Aedes triseriatus mosquito. It then replicates at the site of the bite and then gradually spreads to various sites in the body, in particular the liver, spleen and the lymph nodes.

At this stage, nonspecific symptoms of California encephalitis start appearing. Meanwhile, the virus keeps multiplying and the viral loads keeps on increasing.

The virus spreads to other sites of the body as well. When it finally enters the central nervous system through the cerebral capillary endothelial cells or the choroid plexus, the signs and symptoms of encephalitis as well as various other neurological signs are seen.

In endemic areas, control of the vector (by insecticide sprays, mosquito mats and coils); and application of measures against mosquito bites (e.g. the use of mosquito repellant sprays, mosquito nets etc.) is very useful in preventing California encephalitis [10].

California encephalitis is a caused by an arbovirus belonging to the Bunyaviridae family. It is transmitted by the bite of the mosquito Aedes triseriatus.

Discovered first in Kern County, California, this disease almost exclusively affects children.

California encephalitis is caused by a virus that is transmitted by the bite of a specific mosquito. It is more common in the Midwestern areas of the United States.

Initially, there is fever, headache, vomiting and abdominal pain. Later, when the virus reaches the brain, there is stiffness of the neck and diminishing of consciousness. Seizures and coma also occur.

The treatment for California encephalitis is mainly supportive.

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2. Chun RW, Thompson WH, Grabow JD, Matthews CG. California arbovirus encephalitis in children. Neurology. Apr 1968;18(4):369-375.
3. Rust RS, Thompson WH, Matthews CG, Beaty BJ, Chun RW. La Crosse and other forms of California encephalitis. Journal of child neurology. Jan 1999;14(1):1-14.
4. El Said LH, Vorndam V, Gentsch JR, et al. A comparison of La Crosse virus isolated obtained from different ecological niches and an analysis of the structural components of California encephalitis serogroup viruses and other bunyaviruses. The American journal of tropical medicine and hygiene. Mar 1979;28(2):364-386.
5. Chernesky MA. Transmission of California encephalitis virus by mosquitoes. Canadian journal of microbiology. Jan 1968;14(1):19-23.
6. Walker N. The eastern treehole mosquito, Aedes triseriatus. Wing Beasts. 1992;3(2).
7. Taylor MR, Carpenter DE, Currier RD, Lockwood WR. California encephalitis virus causes subacute encephalomyelitis in an adult. Archives of neurology. Jan 1985;42(1):88-89.
8. Glaser CA, Gilliam S, Schnurr D, et al. In search of encephalitis etiologies: diagnostic challenges in the California Encephalitis Project, 1998-2000. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. Mar 15 2003;36(6):731-742.
9. Jamnback TL, Beaty BJ, Hildreth SW, Brown KL, Gundersen CB. Capture immunoglobulin M system for rapid diagnosis of La Crosse (California encephalitis) virus infections. Journal of clinical microbiology. Sep 1982;16(3):577-580.
10. Francy DB. Mosquito control for prevention of California (La Crosse) encephalitis. Progress in clinical and biological research. 1983;123:365-375.