Tick-Borne Encephalitis: Understanding Symptoms and Stages

Tick-borne encephalitis (TBE) is an acute infectious disease of the central nervous system caused by the tick-borne encephalitis virus, which belongs to the Flavivirus genus. The disease is primarily transmitted through the bite of infected ticks. The clinical progression of TBE typically follows four distinct phases.

Phase 1: Incubation Period

The first stage is the incubation period, which generally lasts between 10 to 15 days. During this time, the virus replicates within the body, but no symptoms are yet visible. Most individuals are unaware they have been infected during this phase.

Phase 2: Prodromal Period

The second phase is known as the prodromal period. Common symptoms include mild fever, dizziness, fatigue, general malaise, and body aches. In cases where the illness develops rapidly, symptoms can intensify within one to two days and reach their peak quickly. This early phase often resembles a mild flu-like condition, making it difficult to diagnose without further complications.

Phase 3: Acute Illness Period

The third and most severe stage is the acute phase. Patients typically experience high fever, often ranging from 39 to 41 degrees Celsius, which can last for five to ten days. This stage is marked by systemic toxicity, with symptoms such as facial and neck flushing, conjunctival congestion, and a slow pulse.

In more severe cases, myocarditis may develop, leading to increased heart rate and changes in the T wave on an electrocardiogram (ECG). Neurological complications can also arise, including disturbances in consciousness and mental function. These may range from drowsiness and emotional blunting to confusion and coma. Some patients may also experience delirium or disorientation.

Additionally, signs of meningeal involvement are common, with intense headaches—especially in the temporal and occipital regions—often described as explosive or throbbing. Muscle paralysis is another possible symptom, typically affecting the neck, shoulder, and upper limbs more than the lower limbs or facial muscles. Other neurological manifestations include tremors and involuntary movements.

Phase 4: Recovery Period

The final stage is the recovery phase, which usually lasts around 10 days on average. During this time, body temperature gradually returns to normal, and neurological symptoms begin to subside. Paralysis of the limbs improves progressively, and cognitive functions typically return to baseline as the patient regains full awareness and physical strength.

Tick-borne encephalitis is a serious condition that requires prompt medical attention. Understanding its progression through these four phases can help both patients and healthcare providers better manage the illness. Preventive measures such as vaccination and avoiding tick-infested areas are crucial for reducing the risk of infection, especially in endemic regions.