Burton's Microbiology Chapter 18: Viral Infections of Humans

How Do Viruses Cause Disease?

• Viruses multiply within host cells, causing cell destruction during their escape, leading to symptoms of a viral infection
• Symptoms vary depending on the location of the infection

Viral Infections of the Skin

• Chickenpox and shingles: caused by Varicella-zoster virus (DNA virus, also known as human herpesvirus 3)
• German measles (rubella): caused by Rubella virus (RNA virus)
• Measles (hard measles, rubeola): caused by Measles (rubeola) virus (RNA virus)
• Monkeypox: caused by Monkeypox virus (DNA virus)
• Smallpox: caused by Variola virus (DNA virus)
• Warts: caused by at least 70 different types of human papillomaviruses (HPV, DNA viruses)

Viral Infections of the Eyes

• Adenoviral conjunctivitis and keratoconjunctivitis: caused by various types of adenoviruses
• Herpes simplex and varicella-zoster viruses can also cause keratoconjunctivitis
• Hemorrhagic conjunctivitis: caused by adenoviruses and enteroviruses
• Retinitis: mostly caused by cytomegalovirus (CMV)

Viral Infections of the Respiratory System

• Common cold (acute viral rhinitis, acute coryza): caused by many different viruses, including rhinoviruses, coronaviruses, parainfluenza viruses, respiratory syncytial virus (RSV), human metapneumovirus, influenza viruses, adenoviruses, and enteroviruses
• Viral infections of the lower respiratory tract:
  • Acute, febrile, viral respiratory disease: caused by parainfluenza viruses, respiratory syncytial virus (RSV), adenovirus, rhinoviruses, certain coronaviruses, coxsackieviruses, and echoviruses
  • Avian influenza (bird flu): caused by avian influenza virus type A
  • Hantavirus pulmonary syndrome (HPS): caused by at least five different hantaviruses
  • Influenza (flu): caused by influenza viruses, types A, B, and C
  • Middle East respiratory syndrome (MERS): caused by MERS-associated coronavirus (MERS-CoV)

Viral Infections of the Oral Region

• Cold sores (fever blisters, herpes labialis): usually caused by herpes simplex virus type 1 (HSV1), but can be caused by herpes simplex type 2 (HSV-2)

Viral Infections of the Gastrointestinal Tract

• Viral gastroenteritis (viral enteritis, viral diarrhea): caused by enteric adenoviruses, astroviruses, sapoviruses, caliciviruses, and rotaviruses
• Transmission occurs via infected humans, most often by way of the fecal–oral route, and possibly from contaminated water and shellfish

Viral Infections of the Genitourinary System

• Viral hepatitis:
  • Type A hepatitis (HAV infection, infectious hepatitis, epidemic hepatitis): caused by Hepatitis A virus (HAV), with fecal–oral transmission
  • Type B hepatitis (HBV infection, serum hepatitis): caused by Hepatitis B virus (HBV), with sexual transmission or household contact with an infected person
  • Type C hepatitis (HCV infection, non-A non-B hepatitis): caused by Hepatitis C virus (HCV), primarily parenterally transmitted
  • Type D hepatitis (HDV infection, delta hepatitis): caused by Hepatitis D virus (HDV, delta virus), with exposure to infected blood and body fluids
  • Type E hepatitis: caused by Hepatitis E virus (HEV), with fecal–oral transmission
• Viral STDs:
  • Anogenital herpes viral infections (genital herpes): caused by either HSV-1 or HSV-2, transmitted via infected humans by direct sexual contact