ARBOVIRUSES

• EPIDEMIOLOGY: Insect spread.
• Mosquito-born viruses: prevalent in summer generally.
• Tick-born viruses: Prevalent year-around.
• MANIFESTATIONS: Usually asymptomatic, but may be severe disease. 4-7 incubation period for clinical symptoms.
• Initial Infection: Viruses will replicate in vascular endothelial cells, in subclinical infection.
• VIREMIA: Most common mild disease. Fever, arthralgia, rash, nausea, vomiting.
• Dengue Fever: Most common cause
• Sindbis virus
• Colorado Tick Fever
• HEMORRHAGIC FEVER: Extensive hemorrhages from almost any epithelial surface. Can lead to CV collapse and death. Fatality rate ranges from 2% - 50%.
• Dengue Virus: Dengue Shock Syndrome
• Yellow Fever: Hemorrhagic fever with hepatitis.
• ENCEPHALITIS:
• From highest to lowest lethality:
• Eastern Equine Encephalitis
• St. Louis Encephalitis
• Western Equine Encephalitis
• California
• Symptoms:
• Starts with Meningitis -- fever, headache, vomiting, stiff neck.
• Followed by lethargy, confusion, paralysis, and coma and death in most serious cases.
• May see neuropsychiatric sequelae in non-fatal cases, such as mental retardation, paralysis.

• IMMUNITY: Acquired and lifelong.
• DIAGNOSIS: Must use serology. Acute:convalescent titers, or IgM.

Category: Microbiology Notes