Lecture%2010

Lecture%2010 - Enteroviruses Enterovirus A virus that...

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Enteroviruses
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Enterovirus A virus that enters the body through the GI tract and thrives Moves on to attack to the nervous system Small viruses made of RNA and protein Cause 10-15 million or more symptomatic infections/yr in US
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Diseases caused by Enteroviruses Special group within the PICORNAVIRUS family “small RNA viruses” Transmitted by fecal-oral route Not listed as gastroenteritis-causing viruses Intestinal symptoms are minor compared to the real damage they can do to other organs
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Enteroviruses Polio virus Hepatitis A virus (HAV) Coxsackie virus EchoVirus
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Polio virus History: Known for centuries, transmission of the virus only recently understood Poliomyelitis 3 types of poliovirus The disease: Infective dose: Not known Incubation period: several days
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Mechanism of action Virus enters through mouth, multiplies in throat and GI tract Moves into bloodstream and carried to CNS Replicates and destroys motor neuron cells Motor neurons control muscles for swallowing, circulation, respiration trunk, arms and legs
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Human nerve cells have protruding protein structure on their surface Poliovirus encounters them and attach Infection begins Once inside, virus hijacks cell’s assembly process Makes copies within hours Kills cell and spreads to other cells
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Symptoms and illness duration 1 st phase-diarrhea, associated with intestinal colonization. Lasts ~week, but virus excreted for several weeks 2 nd phase-viremia (virus in the blood) 3 rd phase-CNS infection and paralysis Illness duration: 1-2 weeks typical: most people have only first phase. Older the victim, more likely will disease progress to 2 nd and 3 rd stages
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Transmission and Control Intestinal infection results in lifelong immunity Infection among young infants (common in areas of poor sanitation) Leads to lower incidence of paralytic disease among children and adults NOTE: infants can also get the paralytic disease, frequency of virus migration to CNS is much lower
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Transmission and Control If sanitation is good, paralytic occurs most often among
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Lecture%2010 - Enteroviruses Enterovirus A virus that...

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