If bitten by an encephalitic tick, when do symptoms appear? - briefly
Symptoms usually develop within 7–14 days after the bite, though onset can be delayed up to a month in some cases.
If bitten by an encephalitic tick, when do symptoms appear? - in detail
A bite from a tick infected with the tick‑borne encephalitis (TBE) virus initiates an incubation period that typically lasts 7–14 days. The interval can be shorter, as few as 3 days, or longer, extending up to 28 days, depending on viral strain, inoculum size, and host factors such as age and immune status.
During the incubation phase the patient feels well; no rash or systemic signs appear. When the virus reaches the central nervous system, the first clinical manifestations emerge. Early symptoms often include:
- Sudden high fever
- Severe headache, especially behind the eyes
- Nausea or vomiting
- General weakness and fatigue
- Muscle or joint pain
These prodromal signs persist for 1–3 days and may be mistaken for a common viral infection. In many cases they resolve spontaneously, entering a second phase characterized by neurological involvement:
- Neck stiffness and photophobia
- Confusion, irritability, or reduced consciousness
- Motor deficits such as tremor, ataxia, or paralysis
- Seizures in severe cases
The neurological phase can begin 2–7 days after the initial fever, and its duration ranges from a few days to several weeks. Recovery may be complete, but persistent deficits—particularly cognitive impairment, gait disturbances, or hearing loss—occur in up to 30 % of patients.
Factors influencing the timing and severity of symptom onset include:
- Tick species and viral genotype – certain strains produce shorter incubation.
- Location of bite – bites on the scalp or face may deliver virus closer to the brain.
- Host immunity – prior vaccination or previous exposure shortens incubation and lessens severity.
- Age – children and the elderly often experience more rapid progression.
Prompt medical evaluation after a suspected tick bite is essential. Laboratory confirmation (serology for IgM/IgG antibodies or PCR) should be performed as soon as fever develops. Early supportive care and, where indicated, antiviral therapy can improve outcomes.