What is encephalitis?

Encephalitis is an inflammatory disease caused by the invasion of pathogens into the brain parenchyma, and it can be divided into acute and subacute. The clinical manifestations are high fever, headache, vomiting, and coma, so we must pay attention to prevent viral invasion.

1. Encephalitis refers to an inflammatory lesion caused by the invasion of pathogens into the brain parenchyma. Depending on the scope of the cause, it can be divided into broad and narrow sense. In a narrow sense, it refers to the inflammatory changes caused by direct invasion of the brain parenchyma by pathogenic microorganisms. Usually a narrow concept is used. The vast majority of causes are viruses, but they can also be caused by infections such as bacteria, fungi, spirochetes, rickettsia, parasites, etc. Some may be allergic diseases, such as acute disseminated encephalomyelitis. Encephalitis usually refers to viral encephalitis and post-infectious encephalomyelitis, which is acute disseminated encephalomyelitis. According to the course of the disease, it is divided into acute, subacute and chronic; according to the pathogenic microorganisms, it is divided into bacterial, fungal, viral, etc.; according to the epidemic situation, it is divided into epidemic and sporadic. Encephalitis can occur in different genders and ages, and is usually acute or subacute. Clinically, it is characterized by symptoms such as high fever, headache, vomiting, coma, and convulsions, most of which are accompanied by changes in cerebrospinal fluid composition. Prevention and treatment should be carried out according to different causes.

2. Viruses

Viruses do not have a cell structure and are divided into two categories based on the different nucleic acid components: one is deoxyribonucleic acid viruses (DNA viruses): including parvoviruses, papillomaviruses (which cause progressive multifocal leukoencephalopathy), adenoviruses, herpes viruses, and varicella-zoster viruses. The other is the RNA virus: including picornaviruses (poliovirus, coxsackievirus, ECHO virus), arboviruses, orthomyxoviruses (influenza virus), paramyxoviruses (measles virus and mumps virus), arenaviruses (lymphocytic choriomeningitis virus), and rhabdoviruses (rabies virus). Viral encephalitis can be divided into acute, subacute and chronic encephalitis according to the severity of onset. According to the type of virus and the route of infection, it can be divided into arbovirus, enterovirus, respiratory virus, herpes virus encephalitis, etc. Depending on the incidence of the disease, it can be divided into epidemic and sporadic encephalitis. It is generally believed that acute encephalitis represents acute viral infection, while subacute or chronic onset such as subacute sclerosing panencephalitis and corticostriatal spinal cord degeneration represent chronic viral infection.

3. Others

Bacteria (Bartonella bacilli (Oroya fever), Bartonella and other species of the genus (cat scratch disease), Listeria monocytogenes, Mycoplasma pneumoniae, Gram-positive rod-shaped bacilli, Mycobacterium tuberculosis), Rickettsia (Eckertsia granulocyticus, Q fever Rickettsia, Ehrlichia chaffeensis, Rickettsia rickettsii, Borrelia burgdorferi, Treponema pallidum), fungi (Coccidioides immitis, Cryptococcus neoformans, Histoplasma capsulatum), parasites (Amoeba, Plasmodium falciparum, Toxoplasma gondii, Trypanosoma brucei gambiae subspecies, Trypanosoma brucei ivanica subspecies, Baylisascaris raccoon roundworm, Gnatostoma spp., Taenia solium), etc. can all cause encephalitis.