Infectious Diseases: RNA Viruses and Symptoms

RNA Viruses that Infect Humans

• Orthomyxoviruses are spherical particles with an average diameter of 80-120 nm.
• Hemagglutinin is a receptor binding membrane fusion glycoprotein produced by influenza viruses that binds to receptors in RBCs, leading to clumping.
• Antigenic drift is a kind of genetic variation resulting from the accumulation of mutations in the virus genes that code for surface proteins recognized by the host body.
• Antigenic shift is the process by which two or more different viruses combine to form a new subtype with a mixture of surface antigens from different animal hosts.

Viral Diseases

• Measles is an acute disease caused by Morbillivirus, also known as red measles or rubeola.
• Rubella or German measles is somewhat similar to measles.
• Yellow fever is the best-known arboviral disease.
• Dengue fever is caused by a flavivirus and is also carried by Aedes mosquitoes.
• PLEURODYNIA is an acute disease characterized by recurrent sharp, sudden intercostal or abdominal pain accompanied by fever and sore throat.
• Acquired Immunodeficiency Syndrome (AIDS) is the cluster of symptoms resulting from the degradation of the immune system by HIV.

Viral Replication and Transmission

• Reverse Transcriptase (RT) is an enzyme that catalyzes the replication of double-stranded DNA from single-stranded RNA.
• Highly Active Antiretroviral Therapy (HAART) is the most effective strategy in the battle against HIV, using multiple drugs simultaneously to interrupt the HIV multiplication cycle at several points.

Viral Classification

• Rhinoviruses are a large group of picornaviruses (over 110 serotypes) associated with the common cold.
• Caliciviruses are an ill-defined group of enteric viruses found in humans and mammals.
• Norovirus is the best-known human pathogen, also known as the Norwalk agent.
• Reoviruses have an unusual double-stranded RNA genome and both an inner and an outer capsid.
• Rotavirus is a significant cause of diarrhea in newborn humans, calves, and piglets.

Prions and Neurological Disorders

• Prions are incredibly hardy "pathogens" highly resistant to chemicals, radiation, and heat.
• Transmissible spongiform encephalopathies (TSEs) are neurodegenerative diseases with long incubation periods but rapid progressions once they begin.
• Poliomyelitis (polio) is an acute enteroviral infection of the spinal cord that can cause neuromuscular paralysis.
• Spastic paralysis is characterized by weakness or paralysis and reduced muscle tone without other obvious cause.

Environmental Microbiology

• Biosphere contains all physical locations on earth that support life, including the thin envelope of life that surrounds the earth's surface and extends some distance into the crust.
• Decomposers, primarily microbes inhabiting soil and water, break down and absorb the organic matter of dead organisms.
• Biomes are large assemblages of organisms that have adapted to a distinct geography and climate and are characterized by dominant life forms, usually plants.
• Communities are composed of mixed assemblages of organisms that live together at the same place and time and that usually exhibit well-defined nutritional or behavioral interrelationships.
• Food chains represent feeding relationships showing the flow of energy and nutrients through a series of organisms in an ecosystem.
• Food webs reflect the actual nutritional structure of a community.