The expert warned about the risk of encephalitis against the background of influenza and acute respiratory viral infections

At the height of the flu season and other respiratory infections, most people perceive complications as pneumonia, bronchitis, or lingering weakness. However, inflammation can affect not only the respiratory tract, but also the central nervous system. Dmitry Bulanov, Director of the Department of Pathomorphology and Clinical Cytology at the LabQuest Laboratory, Candidate of Medical Sciences, told Izvestia on February 22.

"Encephalitis is an inflammation of the brain tissue. Simply put, the brain reacts to damage by inflammation and swelling, which leads to disruption of its functions. This may be manifested by confusion, unusual behavior, seizures, weakness in the limbs, and speech disorders. Unlike "just a high fever," encephalitis affects the central nervous system, and hospitalization is often required," the expert said.

He noted that infection is one of the most common causes of encephalitis, but not the only one. Inflammation can be infectious, when the pathogen involves the nervous tissue, and autoimmune, or post-infectious, when the immune system mistakenly attacks brain structures days or weeks after the infection. These mechanisms require a different approach to treatment, so accurate diagnosis is crucial.

In the public consciousness, encephalitis is most often associated with ticks and "distant regions." This is a noticeable simplification. Tick-borne encephalitis is really relevant in endemic areas and with seasonal tick activity, however, brain inflammation is widespread and has many causes. One well—known example is herpetic encephalitis associated with the herpes simplex virus, which is unrelated to ticks and can occur in any region.

In addition to tick-borne viruses, herpes viruses, enteroviruses, measles and a number of other infections can cause encephalitis. Influenza and COVID-19 occupy a special place among respiratory infections. Neurological complications are rare, but clinically significant. The medical literature describes cases of damage to the central nervous system and other respiratory viruses, including adenovirus and respiratory syncytial virus, but such situations require careful medical assessment.

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The complication may develop against the background of influenza or common acute respiratory viral infections, although this occurs infrequently. The mechanism can be different. In some patients, inflammation is associated with an excessive immune response, when a pronounced inflammatory response affects the nervous tissue. In other cases, vascular and metabolic disorders play an important role against the background of severe infection. Direct involvement of the virus in brain tissue is also possible, but it is not the only scenario.

According to the expert, it's not so much the temperature figures that should be alarming, as the appearance of neurological symptoms. "Red flags" include confusion or disorientation, severe drowsiness, seizures, a sudden change in behavior, speech disorders, weakness or numbness of the extremities, increasing intense headache, repeated vomiting, loss of consciousness. If such signs appear, urgent medical attention is required.

An increased risk of severe course is traditionally noted in children, the elderly, patients with immunodeficiency and serious chronic diseases. However, a young age by itself does not guarantee complete safety. Rare but severe neurological complications have also been described in patients without concomitant pathology, especially with influenza. Therefore, you should focus not on age, but on the nature of the symptoms and the rate of deterioration.

Confirmation of the diagnosis is based on the clinical picture and examination data of the nervous system. The key methods are lumbar puncture with examination of cerebrospinal fluid, including PCR diagnostics of infectious causes, and magnetic resonance imaging of the brain. According to the indications, electroencephalography is performed to detect convulsive activity. Routine blood tests may reflect the inflammatory process, but they do not confirm or exclude encephalitis by themselves.

Bulanov noted that three areas help to reduce the risk. The first is infection prevention: vaccination against influenza and COVID—19 reduces the likelihood of illness and, consequently, the risk of rare severe complications. The second is protection measures against tick—borne infections in endemic regions, including vaccination against tick-borne encephalitis and the use of protective equipment when visiting natural areas. The third is careful monitoring of the condition and early access to a doctor when neurological symptoms appear. If encephalitis is suspected, timely hospitalization and treatment significantly improve the prognosis.

Earlier, on February 6, Lyubov Stankevich, Candidate of Medical Sciences, Director of Laboratory medicine and Production at the LabQuest medical company, told Izvestia that acute respiratory viral infections are often perceived as a mild illness accompanied by a runny nose, cough and fever. However, in practice, any respiratory infection, both viral and bacterial, can lead to serious complications.

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