Chapter 25

Pathogenic RNA viruses

Rhinoviruses

Common cold

Infection limited to upper respiratory tract

Transmission: aerosols, fomites, hand-to-hand contact

Preventative measure: handwashing

Noroviruses (aka Norwalk-like)

Stomach flu

Transmission: ingestion via contaminated food or water

Gastroenteritis

Rubella virus

Rubella (German measles)

Rash of flat pink to red spots

Complications: Adults-arthritis or encephalitis, Pregnant women-congenital defects or death of child

Transmission: respiratory droplet, highly contagious

Vaccine available

Hepatitis A

Fecal-oral route

Jaundice and anorexia

Vaccine available

Hepatits C

Chronic disease

Transmission: shared needles, organ transplants, and sexual activity

Jaundice and dark urine

No vaccine available

Hepatitis D

Transmission: sexual activity and contaminated needles

Hepatitis D requires hepatitis B to become virulent- lacks attachment glycoproteins

Hepatitis B vaccine protects against hepatitis D

Hepatitis E

Enteric hepatitis

Mild infection except for pregnant women (mortality rate 10-30% in third trimester)

Transmission: fecal-oral

No vaccine

Human Immunodeficiency virus (HIV)

Retrovirus- mutation of simian immunodeficiency virus

Transcribes dsDNA from ssRNA using reverse transcriptase

Destroys- T helper, dendritic cells, macrophages, smooth muscle

Treatment: cocktail of antiviral drugs

No vaccine

Acquired Immunodeficiency Syndrome (AIDS)

Not disease, syndrome

Caused by HIV

Measles (Rubeola) virus

Measles or red measles

Koplik’s spots and flat, macular rash

Complications: pneumonia, encephalitis

Transmission: respiratory droplets; spread requires large, dense populations of people

Vaccine available

Mumps Virus

Mumps

Transmission: Respiratory secretions

Infects upper respiratory tract, then spreads to other organs

Meningitis, pancreatitis, inflammation of ovaries or testes, sterility

Vaccine available

Hemorrhagic Fevers

Marburg and Ebola virus

Spread by contaminated body fluids and syringes

Virions attack many cells, specifically macrophages and liver cells

90% mortality rate

Influenza characteristics

Segmented genome

High rate of mutation

Genome highly variable, especially glycoprotein spike (H and N proteins)

Vaccine available

Antigenic drift (slow and gradual, collection of mutations) and shift (two types of virus infect the same animal and swap some of their genome)

Influenza disease

Influenza (flu)

Symptoms caused by interferon and other cytokines

Transmission: respiratory droplet

Rarely attack cells outside lungs

Increased susceptibility to secondary infections