Fundamentals of Microbiology

5.2.1 Viral types and Diseases

Group and type of virus	Description of disease
1. Double-stranded DNA Viruses Papilloma virus Small virus that causes tumors Herpesvirus Medium to large size enveloped virus Herpes simples virus (human herpes virus – HHV) Poxvirus Very large, enveloped, brick-shaped virus Variolavirus	Replication of the viurs within epithelial cells causes warts, which are rough, elevated benign tumors on the skin, urinary tract, or geruitals Replication of the virus within epithelial cells causes fever blisters, which are painful or itchy recurrent vesicular lesions usually or the lips or genitals; the virus goes into a dormant stage by entering nerve cells so that the body retains the virus; recurrent outbreaks of symptoms occur; genital herpes is a sexually transmitted disease Replication of the virus causes smallpox, a deadly disease that has been eliminated
2. Single-stranded (Plus-strand) RNA Viruses Picornavirus Very small, nonen-veloped virus that infects the respiratory tract or gastrointestinal tract Poliovirus Rhinovirus Hepatitis A virus (HAV) Hepatitis C virus (HCV)	Replication of the virus can occur in various body tissues; replication within the nervous system can cause poliomyelitis (commonly caled polio or infantile paralysis) in some cases, viral replication within the spinal column causes meningitis; the virus is ofren transmitted via contaminated food or water Replication of the virus within the respiratory tract causes the common cold, bronchitis, and croup, which usually are characterized by congestion, coughing, sneezing, and a mild fever Replication of the viurs within the liver causes infectious hepatitis (hepatitis A), which is characterized by a high fever and jaundice (yellowing of the skin due to loss of lover function); the virus is often transmitted via contaminated food or water Replication of this virus within the liver causes hepatitis C, which is also called non-A, non-B hepatitis; hepatitis C is characterized by a high fever and jaundice
3. Single-stranded (Minus-strand) RNA Viruses Orthomyxovirus Medium to large size, enveloped virus Influenza A, B, and C virus Paramyxovirus Medium to large size, enveloped virus Measles virus Mumps virus Rhabdovirus Medium-size, enveloped, bullet-shaped virus Rabies virus	Replication of these viruses within the respiratory tract causes influenza, which is commonly called flu; influenza is charaterized by a high fever, cough malaise, and body ache Replication of this virus causes measles, which is characterized by a red skin rash, high fecer, cough, and malaise Replication of the virus causes mumps, which is charaterized by swelling of one or both salivary glands Replication of the virus within the nervous system causes rabies, which is initially characterized by sensitivity to stimuli such as light and noise, difficulty in swallowing, a fear of water (hydrophobia), followed by delirium, coma, and death; the disease is usually transmitted via the bites of infected animals or in some cases by inhalation and is prevented by vaccination
4. Double – stranded RNA Viruses Reovirus Rotavirus Small, naked virus	Replication of the viurs within the gastrointestinal tract causes acute infantile gastroenteritis characterized by severe diarrhea that is a common disease in children
5. Double-stranded RNA Viruses Contraining Reverse Transcription Retroviruses Medium – size enveloped virus Human immunodeficiency virus (HIV)	Replication of the virus within T lymphocytes of the immune defense system causes acquired immunodeficiency syndrome (AIDS), which is characterized by a loss immune defenses against infections, leading to opportunistic infections by various pathogens and eventual death