Encephalitis: what kind of disease it is, types, and tick-borne encephalitis

Encephalitis is inflammation of the brain. The condition is rare but serious: it requires emergency care in a hospital and can be life-threatening. Below is what is known about the disease, its types, and tick-borne encephalitis.

What encephalitis is

Encephalitis is inflammation (swelling) of the brain. It develops when an infection or another condition affecting the brain activates the immune system. In extreme cases, the inflammation leads to brain damage, stroke, or death. The disease is not transmitted from person to person. Anyone can become ill, but the risk is higher in young children, older adults, people with weakened immunity, and those who live where ticks and mosquitoes — carriers of viruses — are common.

Types of encephalitis and their causes

There are two main types: infectious and autoimmune. Infectious encephalitis is most often caused by viruses: herpesviruses (herpes simplex, Epstein-Barr virus, varicella-zoster virus); pathogens transmitted by a tick bite (tick-borne encephalitis virus, Powassan virus) or a mosquito bite (Japanese encephalitis, West Nile fever, La Crosse virus); enteroviruses with summer-autumn seasonality. Bacteria, fungi, and parasites cause it less often. Autoimmune encephalitis occurs when the immune system mistakenly attacks healthy brain cells; it can be triggered by certain tumors and infections, and sometimes the cause remains unknown.

Tick-borne encephalitis: the causative agent and route of infection

Tick-borne encephalitis is caused by the neurotropic tick-borne encephalitis virus. Its vectors and reservoir are the ixodid ticks Ixodes persulcatus and Ixodes ricinus. In natural foci, the virus circulates between ticks and wild animals — rodents and birds; in human-modified landscapes, goats and cows can serve as the reservoir. Humans become infected through a bite. Alimentary transmission is also possible — through raw milk and dairy products from infected animals. Seasonality coincides with tick activity: a peak in May–June, and a second rise in August–September. The proportion of asymptomatic forms among the local population can reach 90%, and a clinically pronounced form develops in approximately 2% of people bitten by virus-carrying ticks. The incubation period after a bite is 1 to 30 days, more often 7–14; with infection through milk — 4–7 days.

Viral encephalitis: how it develops

When a bite occurs, the virus immediately enters the blood and penetrates the central nervous system through hematogenous dissemination and viremia. Tick-borne encephalitis begins suddenly: the temperature rises rapidly to 38–39 °C, severe headache, weakness, nausea, sometimes vomiting appear, and sleep is disturbed. The febrile form resolves within 3–5 days and proceeds without damage to the nervous system — it is one of the most common, but is rarely diagnosed. In the meningeal form, neck muscle rigidity, Kernig and Brudzinski signs occur, and fever lasts 10–14 days. The meningoencephalitic form is more severe: lethargy and drowsiness increase, delirium and hallucinations appear, and seizures are possible.

Symptoms and possible complications

The disease often begins with flu-like symptoms — high fever and headache. Some people have no symptoms at all, while others have mild manifestations: fever, fatigue, headache, and muscle pain. In infants the picture is different: lethargy, poor feeding, vomiting, body stiffness, unusual irritability, bulging fontanelle. More serious signs appear within hours, days, or weeks:

• confusion and disorientation;
• seizures;
• changes in personality and behavior;
• difficulty speaking;
• weakness or loss of movement in parts of the body, loss of consciousness.

After inflammation, many people are left with long-term consequences: memory loss, frequent seizures, changes in personality and behavior, problems with attention, concentration, and planning, persistent fatigue. Some people recover fully, but recovery can be long. A hospital stay lasts from several days to several weeks and even months.

How it is diagnosed and when urgent help is needed

The doctor performs an examination, takes a medical history, and conducts a neurological examination. Diagnosis uses computed tomography or MRI of the brain, electroencephalography, blood tests, and cerebrospinal fluid tests. Care is provided in a hospital: the earlier it is started, the higher the chances, and its scope depends on the cause and is determined by the doctor.

Call 103 or 112 if a person develops confusion, seizures, changes in personality and behavior, difficulty speaking, weakness or loss of movement in parts of the body, or loss of consciousness.

This material is for reference: it does not replace a doctor's consultation, and the decision on diagnosis and care is made by a specialist.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer