Polioencephalitis | |
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Specialty | Neurology/infectious disease |
Polioencephalitis is a viral infection of the brain, causing inflammation within the grey matter of the brain stem. [1] The virus has an affinity for neuronal cell bodies and has been found to affect mostly the midbrain, pons, medulla and cerebellum of most infected patients. The infection can reach up through the thalamus and hypothalamus and possibly reach the cerebral hemispheres. [2] The infection is caused by the poliomyelitis virus which is a single-stranded, positive sense RNA virus surrounded by a non-enveloped capsid. Humans are the only known natural hosts of this virus. The disease has been eliminated from the U.S. since the mid-twentieth century, but is still found in certain areas of the world such as Africa. [3]
Signs and symptoms may vary and some individuals may not experience any symptoms at all. The most common reported symptom of polioencephalitis is fatigue. Fatigue is associated with difficulty in attention, cognition, and maintaining wakefulness [4] Some individuals experience psychiatric symptoms that include anxious mood, pain, insomnia, and depressed mood. Confusion and disorientation of time and space have also been reported. Motor symptoms vary more from patient to patient, but can include incoordination and tremors, nystagmus, loss of conjugate eye movements, rigidity and hemiparesis. [2]
The poliomyelitis virus is an enterovirus that enters through the mouth and multiplies in the throat and epithelial cells of the gastrointestinal tract. It will then move to the bloodstream and is carried to the central nervous system. Once in the CNS, the virus will attach to a host cell by binding with a cell surface receptor. The host cell surface receptor is a glycoprotein that has been recently identified as CD155. [5] Once the virus has bound to the host cell, it will penetrate the host cell membrane and begin the replication of its genome. Many cells contain the surface receptor CD155; however, manifestation of this disease does not occur in all cells. The reason for incidence of the disease in only certain areas of the brain such as the brainstem is unknown. Once areas of the brain have been invaded by the virus, inflammation will occur. During inflammation, the brain’s tissues become swollen due to the body’s immune system response to the infection. [6] Fluid, white blood cells, dead cellular debris and inactivated viruses resulting from the actions of the immune response can significantly alter the fluid surrounding healthy neurons. The function of these healthy neurons can decline due to disruptions in the cell membrane affecting electrical properties of the neuron or by interfering with the blood supply causing anoxic cellular damage. [7] Depending on which neurons are damaged will result in a variety of different symptoms.
If someone is suspected of having polioencephalitis a sample of throat secretions, stool or cerebrospinal fluid is checked for the virus. Blood tests can be done to detect antibodies against viral antigens and foreign proteins. Virus isolation is the most sensitive method and it is most likely to be isolated from stool samples. Once isolated, RT-PCR is used to differentiate naturally occurring strains from vaccine-like strains. [8]
The virus is most often spread by person to person contact with the stool or saliva of the infected person. Two types of vaccines have been developed to prevent the occurrence and spread of the poliomyelitis virus. The first is an inactivated, or killed, form of the virus and the second is an attenuated, or weakened, form of the virus. The development of vaccines has successfully eliminated the disease from the United States. There are continued vaccination efforts in the U.S. to maintain this success rate as this disease still occurs in some areas of the world. [9]
There is no cure for polioencephalitis so prevention is essential. Many people that become infected will not develop symptoms and their prognosis is excellent. However, the prognosis is dependent on the amount of cellular damage done by the virus and the area of the brain affected. Many people that develop more severe symptoms can have lifelong disabilities or it can lead to death. [10] Supportive treatments include bed rest, pain relievers, and a nutritious diet. [11] Many drugs have been used to treat psychiatric symptoms such as Clonazepam for insomnia and Desvenlafaxine or Citalopram for depressed mood.[ citation needed ]
Research into the mechanism of this disease stalled with the development of the vaccines in the mid-twentieth century. However, with the recent identification of the cell surface receptor CD155 new interest has resurfaced in this disease. Experiments on transgenic mice are investigating the initial sites of viral replication in the host and how the virus moves from the bloodstream into the central nervous system. [5] Research into the host range of the virus has also been of interest. The host range of a virus is determined by the interaction of the virus with host cellular receptors such as CD155. Comparison of the amino acid sequence in the binding domain of the host cell receptor is highly variable among mammalian species. Rapid changes in the sequence of the binding domain have restricted the host range of the poliovirus. [12] Targeting of the brain and spinal cord have also come under investigation. The restricted tropism maybe due to organ specific differences in the initiation of translation by the virus internal ribosome entry site. [13]
Poliomyelitis, commonly shortened to polio, is an infectious disease caused by the poliovirus. Approximately 75% of cases are asymptomatic; mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe symptoms develop such as headache, neck stiffness, and paresthesia. These symptoms usually pass within one or two weeks. A less common symptom is permanent paralysis, and possible death in extreme cases. Years after recovery, post-polio syndrome may occur, with a slow development of muscle weakness similar to that which the person had during the initial infection.
Polio vaccines are vaccines used to prevent poliomyelitis (polio). Two types are used: an inactivated poliovirus given by injection (IPV) and a weakened poliovirus given by mouth (OPV). The World Health Organization (WHO) recommends all children be fully vaccinated against polio. The two vaccines have eliminated polio from most of the world, and reduced the number of cases reported each year from an estimated 350,000 in 1988 to 33 in 2018.
Myelitis is inflammation of the spinal cord which can disrupt the normal responses from the brain to the rest of the body, and from the rest of the body to the brain. Inflammation in the spinal cord can cause the myelin and axon to be damaged resulting in symptoms such as paralysis and sensory loss. Myelitis is classified to several categories depending on the area or the cause of the lesion; however, any inflammatory attack on the spinal cord is often referred to as transverse myelitis.
Coxsackieviruses are a few related enteroviruses that belong to the Picornaviridae family of nonenveloped, linear, positive-sense single-stranded RNA viruses, as well as its genus Enterovirus, which also includes poliovirus and echovirus. Enteroviruses are among the most common and important human pathogens, and ordinarily its members are transmitted by the fecal–oral route. Coxsackieviruses share many characteristics with poliovirus. With control of poliovirus infections in much of the world, more attention has been focused on understanding the nonpolio enteroviruses such as coxsackievirus.
Poliovirus, the causative agent of polio, is a serotype of the species Enterovirus C, in the family of Picornaviridae. There are three poliovirus serotypes: types 1, 2, and 3.
Post-polio syndrome is a group of latent symptoms of poliomyelitis (polio), occurring at about a 25–40% rate. These symptoms are caused by the damaging effects of the viral infection on the nervous system. Symptoms typically occur 15 to 30 years after an initial acute paralytic attack. Symptoms include decreasing muscular function or acute weakness with pain and fatigue. The same symptoms may also occur years after a nonparalytic polio (NPP) infection.
Adenoviruses are medium-sized, nonenveloped viruses with an icosahedral nucleocapsid containing a double-stranded DNA genome. Their name derives from their initial isolation from human adenoids in 1953.
Enterovirus is a genus of positive-sense single-stranded RNA viruses associated with several human and mammalian diseases. Enteroviruses are named by their transmission-route through the intestine.
Viral pathogenesis is the study of the process and mechanisms by which viruses cause diseases in their target hosts, often at the cellular or molecular level. It is a specialized field of study in virology.
Viral encephalitis is inflammation of the brain parenchyma, called encephalitis, by a virus. The different forms of viral encephalitis are called viral encephalitides. It is the most common type of encephalitis and often occurs with viral meningitis. Encephalitic viruses first cause infection and replicate outside of the central nervous system (CNS), most reaching the CNS through the circulatory system and a minority from nerve endings toward the CNS. Once in the brain, the virus and the host's inflammatory response disrupt neural function, leading to illness and complications, many of which frequently are neurological in nature, such as impaired motor skills and altered behavior.
The schedule for childhood immunizations in the United States is published by the Centers for Disease Control and Prevention (CDC). The vaccination schedule is broken down by age: birth to six years of age, seven to eighteen, and adults nineteen and older. Childhood immunizations are key in preventing diseases with epidemic potential.
Herpes simplex virus1 and 2, also known by their taxonomic names Human alphaherpesvirus 1 and Human alphaherpesvirus 2, are two members of the human Herpesviridae family, a set of viruses that produce viral infections in the majority of humans. Both HSV-1 and HSV-2 are very common and contagious. They can be spread when an infected person begins shedding the virus.
CD155, also known as the poliovirus receptor, is a protein that in humans is encoded by the PVR gene. It is a transmembrane protein that is involved in forming junctions between neighboring cells. It is also the molecule that poliovirus uses to enter cells. The gene is specific to the primates.
Host tropism is the infection specificity of certain pathogens to particular hosts and host tissues. This explains why most pathogens are only capable of infecting a limited range of host organisms.
Flaccid paralysis is a neurological condition characterized by weakness or paralysis and reduced muscle tone without other obvious cause. This abnormal condition may be caused by disease or by trauma affecting the nerves associated with the involved muscles. For example, if the somatic nerves to a skeletal muscle are severed, then the muscle will exhibit flaccid paralysis. When muscles enter this state, they become limp and cannot contract. This condition can become fatal if it affects the respiratory muscles, posing the threat of suffocation. It also occurs in the spinal shock stage in complete transection of the spinal cord occurring in injuries such as gunshot wounds.
Vincent R. Racaniello is a Higgins Professor in the Department of Microbiology and Immunology at Columbia University's College of Physicians and Surgeons. He is a co-author of a textbook on virology, Principles of Virology.
Influenza, commonly known as "the flu" or just "flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin from one to four days after exposure to the virus and last for about 2–8 days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia, which can be caused by the virus or by a subsequent bacterial infection. Other complications of infection include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.
Eckard Wimmer is a German American virologist, organic chemist and distinguished professor of molecular genetics and microbiology at Stony Brook University. He is best known for his seminal work on the molecular biology of poliovirus and the first chemical synthesis of a viral genome capable of infection and subsequent production of live viruses.
DTaP-IPV-HepB vaccine is a combination vaccine whose generic name is diphtheria and tetanus toxoids and acellular pertussis adsorbed, hepatitis B (recombinant) and inactivated polio vaccine or DTaP-IPV-Hep B. It protects against the infectious diseases diphtheria, tetanus, pertussis, poliomyelitis, and hepatitis B.
Endothelial cell tropism or endotheliotropism is a type of tissue tropism or host tropism that characterizes an pathogen's ability to recognize and infect an endothelial cell. Pathogens, such as viruses, can target a specific tissue type or multiple tissue types. Like other cells, the endothelial cell possesses several features that supports a productive viral infection a cell including, cell surface receptors, immune responses, and other virulence factors. Endothelial cells are found in various tissue types such as in the capillaries, veins, and arteries in the human body. As endothelial cells line these blood vessels and critical networks that extend access to various human organ systems, the virus entry into these cells can be detrimental to virus spread across the host system and affect clinical course of disease. Understanding the mechanisms of how viruses attach, enter, and control endothelial functions and host responses inform infectious disease understanding and medical countermeasures.