Yellow fever was an epidemic in the U.S. during the 19th century with cases reported as far north as Philadelphia. The last known case happened in New Orleans in 1905 resulting to many deaths. Flavivirus also know as Yellow fever virus is a RNA virus. The enveloped is spherical and about 50 nm in diameter. The surface proteins are composed in an icosahedral-like symmetry (Dao, 2010). Full grown virions contain two virus-encoded membrane proteins (M and E), while immature virions have a membrane protein precursor. The virion RNA is infectious it acts as the genome and viral messenger RNA. The genome transcribe into a polyprotein, then into co-transcribe and post-transcribe by the host and viral proteases (Dao,2010). Polio was another epidemic
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The Polio virus is apart of the genus Enterovirus and a member of the family Picornaviridae (Varner,2009). It is classified as a small, icosahedral shaped, non-enveloped, and a positive sense RNA virus. The organism is heat resistant, tolerates an acidic environment with a pH of 3-5 for up to three hours. The virus can survive for days at room temperature and for weeks at 4°C. It is inactivated by drying, heat, formaldehyde, chlorine, and ultraviolet light (Varner, 2009). In 1993, a major outbreak of severe respiratory disease occurred in the Southwestern United States. It was recognized as a new species of the Hantavirus genus, named the Sin Nombre virus. The virus is enveloped and has a tripartite negative-sense single-stranded RNA genome. The three segments, S,L, and M, code of RNA genome code for a viral transcriptase, polyproteins that are envelope glycoproteins, and nucleocapsid proteins (Smith …show more content…
The viruses grows in oropharyngeal and lower gastrointestinal tract mucosa during the first 1-3 weeks of the incubation period. The virus is secreted in saliva and feces during this period, causing most host-to-host transmission. The poliovirus enters the nervous system by crossing the blood-brain barrier or by axonal transportation from a peripheral nerve. It then causes nervous system infection resulting to asymmetric weakness and muscle atrophy because of the loss of motor neurons and denervation of the skeletal muscles. Even though polio can cause paralysis and death majority of the people who are infected with the poliovirus don't get sick and are never aware they have been infected with polio. Due to the use of the poliovirus vaccine, the incidence rate has been less than 0.01 cases per 100,000 population since 1965. Only a few cases of paralytic poliomyelitis are reported each year in the United
The Polio virus is apart of the genus Enterovirus and a member of the family Picornaviridae (Varner,2009). It is classified as a small, icosahedral shaped, non-enveloped, and a positive sense RNA virus. The organism is heat resistant, tolerates an acidic environment with a pH of 3-5 for up to three hours. The virus can survive for days at room temperature and for weeks at 4°C. It is inactivated by drying, heat, formaldehyde, chlorine, and ultraviolet light (Varner, 2009). In 1993, a major outbreak of severe respiratory disease occurred in the Southwestern United States. It was recognized as a new species of the Hantavirus genus, named the Sin Nombre virus. The virus is enveloped and has a tripartite negative-sense single-stranded RNA genome. The three segments, S,L, and M, code of RNA genome code for a viral transcriptase, polyproteins that are envelope glycoproteins, and nucleocapsid proteins (Smith …show more content…
The viruses grows in oropharyngeal and lower gastrointestinal tract mucosa during the first 1-3 weeks of the incubation period. The virus is secreted in saliva and feces during this period, causing most host-to-host transmission. The poliovirus enters the nervous system by crossing the blood-brain barrier or by axonal transportation from a peripheral nerve. It then causes nervous system infection resulting to asymmetric weakness and muscle atrophy because of the loss of motor neurons and denervation of the skeletal muscles. Even though polio can cause paralysis and death majority of the people who are infected with the poliovirus don't get sick and are never aware they have been infected with polio. Due to the use of the poliovirus vaccine, the incidence rate has been less than 0.01 cases per 100,000 population since 1965. Only a few cases of paralytic poliomyelitis are reported each year in the United