Viral Infections in Humans

How Do Viruses Cause Disease?

• Viruses multiply within host cells
• During escape from host cells, cells are destroyed, 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)
• 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
• People with viral infections should wash hands thoroughly before touching eyes or contact lenses

Viral Infections of the Respiratory System

• The common cold (acute viral rhinitis, acute coryza): caused by many different viruses, including rhinoviruses, coronaviruses, parainfluenza viruses, respiratory syncytial virus (RSV), influenza viruses, adenoviruses, and enteroviruses
• Acute, febrile, viral respiratory disease: caused by parainfluenza viruses, RSV, adenovirus, rhinoviruses, and other viruses
• 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 (RNA viruses)
• Severe acute respiratory syndrome (SARS): caused by SARS-associated coronavirus (SARS-CoV)

Viral Infections of the Oral Region

• Cold sores (fever blisters, herpes labialis): usually caused by Herpes simplex virus type 1 (HSV-1), but can be caused by Herpes simplex type 2 (HSV-2)
• Viral gastroenteritis (viral enteritis, viral diarrhea): caused by enteric adenoviruses, astroviruses, caliciviruses, and rotaviruses

Viral Infections of the Circulatory System

• Human immunodeficiency virus (HIV) infection, acquired immunodeficiency syndrome (AIDS): caused by HIV-1 and HIV-2 (ssRNA viruses)
• Infectious mononucleosis (“mono,” “kissing disease”): caused by Epstein–Barr virus (EBV) (DNA virus)
• Mumps (infectious parotitis): caused by Mumps virus (RNA virus)

Viral Hemorrhagic Diseases (Viral Hemorrhagic Fevers)

• Caused by many different viruses, including dengue virus, yellow fever virus, Crimean-Congo hemorrhagic fever virus, Lassa virus, Ebola virus, and Marburg virus
• Ebola and Marburg viruses are extremely large filamentous viruses
• Infected humans serve as reservoirs; infected African green monkeys also serve as reservoirs in Marburg infection
• Transmission is person-to-person via direct contact with infected blood, secretions, internal organs, or semen; also, needlestick

Viral Infections of the CNS

• Lymphocytic choriomeningitis: caused by Lymphocytic choriomeningitis virus (LCMV)
• Poliomyelitis (polio, infantile paralysis): caused by Polioviruses (RNA viruses)
• Rabies: caused by Rabies virus (bullet-shaped, enveloped RNA virus)
• Viral meningitis (aseptic meningitis, abacterial meningitis): caused by various viruses

Selected Arthropodborne Viral Encephalitides of the United States

• Eastern equine encephalitis (EEE): reservoirs are birds and horses; vectors are mosquitoes
• California encephalitis: reservoirs are rodents and rabbits; vectors are mosquitoes
• LaCrosse encephalitis: reservoirs are chipmunks and squirrels; vectors are mosquitoes
• St. Louis encephalitis: reservoirs are birds; vectors are mosquitoes
• West Nile virus encephalitis: reservoirs are birds and perhaps horses; vectors are mosquitoes
• Western equine encephalitis (WEE): reservoirs are birds and horses; vectors are mosquitoes

This quiz covers various viral infections in humans, including those affecting the skin, ears, eyes, respiratory system, oral region, gastrointestinal tract, and genitourinary system. Learn about how viruses cause disease and the different types of infections they can cause.