Viral Infections Chapter 18

How Do Viruses Cause Disease?

• Viruses multiply within host cells and destroy the cells during their escape, leading to symptoms of a viral infection.

Viral Infections of the Skin

• Chickenpox and Shingles are caused by Varicella-zoster virus (DNA virus, human herpesvirus 3).
• German Measles (Rubella) is caused by Rubella virus (RNA virus).
• Measles (Hard Measles, Rubeola) is caused by Measles (rubeola) virus, an RNA virus.
• Monkeypox is caused by Monkeypox virus, a DNA virus.
• Smallpox is caused by 2 strains of variola virus (variola minor and variola major), a DNA virus.
• Warts are caused by at least 70 different types of human papillomaviruses (HPV), DNA viruses.

Viral Infections of the Upper Respiratory Tract

• The Common Cold (Acute Viral Rhinitis, Acute Coryza) is caused by many different viruses, including:
  • Rhinoviruses (over 100 serotypes)
  • Coronaviruses
  • Parainfluenza viruses
  • Respiratory syncytial virus (RSV)
  • Influenza viruses
  • Adenoviruses
  • Enteroviruses
• Transmission occurs via respiratory secretions, hands, and fomites or direct contact with airborne droplets.

Viral Infections of the Lower Respiratory Tract

• Acute, Febrile, Viral Respiratory Disease is caused by:
  • Parainfluenza viruses
  • Respiratory syncytial virus (RSV)
  • Adenovirus
  • Rhinoviruses
  • Coronaviruses
  • Coxsackieviruses
  • Echoviruses
• Transmission occurs via direct oral contact or airborne droplets.
• Avian Influenza (Bird Flu) is caused by Avian influenza virus type A, with 3 prominent subtypes (H5, H7, H9).
• Transmission occurs via contact with infected poultry or contaminated surfaces.
• Hantavirus Pulmonary Syndrome (HPS) is caused by at least 5 different hantaviruses.
• Transmission occurs via inhalation of aerosolized rodent feces, urine, and saliva.
• Influenza, Flu is caused by Influenza viruses, types A, B, and C (RNA viruses).
• Transmission occurs via infected humans, with pigs and birds serving as reservoirs.
• Severe Acute Respiratory Syndrome (SARS) is caused by SARS-associated coronavirus (SARS-CoV).
• Transmission occurs via infected individuals, respiratory droplets, or touching contaminated surfaces or objects.

Viral Infections of the Oral Region

• Cold Sores (Fever Blisters, Herpes Labialis) are usually caused by Herpes simplex virus type 1 (HSV1), but can be caused by Herpes simplex type 2 (HSV2).
• Both HSV-1 and HSV-2 can also infect the genital tract.

Viral Infections of the GI Tract

• Viral Gastroenteritis (Viral Enteritis, Viral Diarrhea) is caused by:
  • Enteric adenoviruses
  • Astroviruses
  • Caliciviruses
  • Rotaviruses
• Transmission occurs via infected humans, contaminated water, and shellfish.

Viral Hepatitis

• Type A Hepatitis (HAV Infection, Infectious Hepatitis, Epidemic Hepatitis) is caused by Hepatitis A virus (HAV), a linear ssRNA virus.
• Transmission occurs via fecal-oral route.
• Type B Hepatitis (HBV Infection, Serum Hepatitis) is caused by Hepatitis B virus (HBV), an enveloped, circular dsDNA virus.
• Transmission occurs via sexual transmission, household contact, injected drug use, tattooing, and needlesticks.
• Type C Hepatitis (HCV Infection, Non-A Non-B Hepatitis) is caused by Hepatitis C virus (HCV), an enveloped, linear ssRNA virus.
• Transmission occurs primarily via parenteral transmission and rarely via sexual transmission.
• Type D Hepatitis (HDV Infection, Delta Hepatitis) is caused by Hepatitis D virus (HDV, delta virus), an enveloped, circular ssRNA viral satellite.