Contain an RNA polymerase, which makes vRNA that host ribosomes use as mRNA to make viral components.
most polio cases are inapparent. <2% cases end in paralysis. Approx. 12 cases in the U.S. each year. Very stable virus. Vaccine available.
implicated in a number of conditions such as chronic fatigue syndrome; viral heart disease; possibly insulin dependent diabetes.
Hepatitis A (HAV)
usually acquired in poor sanitary conditions or contaminated water, incubation time 2 to 4 weeks, preformed immunoglobulin can prevent 80 to 90% cases. Least dangerous form of viral hepatitis, however, liver damage can result. Vaccine available.
gastroenteritis, acquired via fecal-oral contact, new epidemics appearing in Asia, Africa, and Mexico.
(insect vectors) Birds and rodents are reservoirs. All involve the central nervous system. Equine encephalitis, carried by the Culiseta melanura and Aedes vexans mosquitos can infect humans. Assoc. with swampy regions.
(aka German measles) affects the fetus in first trimester and can cause severe congenital abnormalities including death. Vaccine available.
transmitted by Aedes aegypti mosquitos, causes hemorrhaging in liver and kidneys, mortality 80%. Still endemic in Africa and S. Amer. Vaccine available for travelers.
most common mosquito-transmitted viral infection, hemorrhagic fever, mortality 5 to 30%, military vaccine available
via blood contact. Blood transfusion transmittance is rare, though still possible, since screening began in 1990. Many cases asymptomatic or mild initially. Can become chronic 20 yrs or more. Frequently results in liver damage.
West Nile Virus
carried by Culex pipens mosquito, feeds at night, likes stagnant cool water for breeding, symptoms mimic the flu, can include a rash.
Common colds and severe acute respiratory syndrome (SARS), first reported in China, mortality ~10%,
rabies, bullet-shaped, found in most warm blooded mammals, thought to be asymptomatic in bats. Length of incubation varies in animals. Usually long, therefore immune serum usually works for humans.
Respiratory syncytial virus (RSV)
respiratory infection in kids, milder in adults. Linked to ear infections in children. Highly contagious.
swelling of salivary glands. Meningitis follows in 10% of the cases. May cause sterility in adult males. Vaccine available.
Rubeola (aka measles, hard or red measles)
highly contagious, Koplik's spots are diagnostic, complications can be serious. Vaccine available.
influenza viruses, spikes mutate frequently. Types A, B, & C. Virus destroys the epithelial lining of the respiratory tract thus allowing secondary bacterial infection to enter. Type A strains are responsible for pandemics that occur at intervals of 10 to 20 years. The B strains cause local outbreaks and epidemics less often. Type C strains are rare. Pneumonia is a common secondary infection. A yearly vaccine, based on the predominant A and B strains, is about 70% effective.
hantavirus pulmonary syndrome (HPS), transmitted by rodent excreta, saliva, or urine. After HIV and rabies, the most lethal virus in the U.S. Incubation 1 to 5 wks.
long, thread-like viruses that often take the shape of a fishhook, cause viral hemorrhagic fevers, spread by direct contact with infected blood, Ebola virus fatality 90%, Marburg virus fatality 25%
enveloped, contain enzyme - reverse transcriptase, which makes DNA from vRNA, inserts new DNA into host DNA. Most are not cytolytic, and may be expressed indefinitely. Many related to cancers.