1. Viruses Are they living or not?

2. Brief History of virus discovery  Are agents that can’t be seen with an ordinary light microscope  Are agents that pass through filters that can trap even the smallest bacteria  The question that arose was are these agents toxins or poisons?  The Latin word for poisons is viruses  Are agents that can’t be seen with an ordinary light microscope  Are agents that pass through filters that can trap even the smallest bacteria  The question that arose was are these agents toxins or poisons?  The Latin word for poisons is viruses

3. Basic Virology  What is a virus?  Is it living or nonliving?  How are they different from other “living” organisms?  Submicroscopic 18-350 nm in size (10 -9 M)  Can only be “seen” with an electron microscope  Obligate intracellular parasites  Viruses have no genes that encode the proteins that function as the metabolic machinery for energy generation  Viruses have no genes that encode the proteins that function as the metabolic machinery for protein synthesis  Viruses may or may not contain the genes that encode enzymes involved in nucleic acid synthesis  What is a virus?  Is it living or nonliving?  How are they different from other “living” organisms?  Submicroscopic 18-350 nm in size (10 -9 M)  Can only be “seen” with an electron microscope  Obligate intracellular parasites  Viruses have no genes that encode the proteins that function as the metabolic machinery for energy generation  Viruses have no genes that encode the proteins that function as the metabolic machinery for protein synthesis  Viruses may or may not contain the genes that encode enzymes involved in nucleic acid synthesis

4. Basic Virology  Biochemically  Have RNA or DNA, not both  Have no small ions or polysaccharides (sugars)  May (enveloped viruses) or may not (naked viruses) contain lipids  Biochemically  Have RNA or DNA, not both  Have no small ions or polysaccharides (sugars)  May (enveloped viruses) or may not (naked viruses) contain lipids

5. Basic Virology

6.  Growth curves of bacteria and viruses are very different Bacterial growth curve Viral growth curve

7. Differences in growth curves:  Virus particles are produced from the assembly of pre-formed components: other organisms grow from an increase in the integrated sum of their components and reproduce by cell division.  Viruses don’t “grow” or undergo division  Virus particles are produced from the assembly of pre-formed components: other organisms grow from an increase in the integrated sum of their components and reproduce by cell division.  Viruses don’t “grow” or undergo division

8. Basic Virology  What is the basic structure of a virus?  Nucleic acid of RNA or DNA – is the genetic information for the virus  Single (SS) or double stranded (DS)  Linear, circular, or nicked  Unsegmented or segmented  If SS RNA, may be of the plus (+) or the minus (-) sense  + RNA – genomic RNA can serve as mRNA and be directly translated into protein  - RNA – genomic RNA cannot serve as mRNA and cannot be translated directly into protein  What is the basic structure of a virus?  Nucleic acid of RNA or DNA – is the genetic information for the virus  Single (SS) or double stranded (DS)  Linear, circular, or nicked  Unsegmented or segmented  If SS RNA, may be of the plus (+) or the minus (-) sense  + RNA – genomic RNA can serve as mRNA and be directly translated into protein  - RNA – genomic RNA cannot serve as mRNA and cannot be translated directly into protein

9. Basic Virology

10.  Protein outer coat – is called the capsid  The capsid is composed of individual subunits called capsomers  What is the function of the capsid?  Protects the delicate inner nucleic acid from harsh environmental conditions  May be involved in attachment to host cells  There are two basic capsid structures  Icosahedral  Helical  Protein outer coat – is called the capsid  The capsid is composed of individual subunits called capsomers  What is the function of the capsid?  Protects the delicate inner nucleic acid from harsh environmental conditions  May be involved in attachment to host cells  There are two basic capsid structures  Icosahedral  Helical

11. Basic Virology Icosahedral Structure

12. Basic Virology Helical structure

13. Basic Virology  Viruses that contain only the viral nucleic acid and the capsid are called naked viruses  Some viruses have an outer lipid layer called an envelope  The envelope is derived from host cell membranes  For viruses that use the plasma membrane as their envelope, the envelope is acquired as the virus exits the host cell via a process called budding  Virally encoded proteins in the envelope play a major role in the viral life cycle.  Proteins in the viral envelope are involved in attachment to host cells.  Proteins in the viral envelope mediate fusion of the virus envelope with host cell membrane during the entry of the virus into the host cell.  Viruses that contain only the viral nucleic acid and the capsid are called naked viruses  Some viruses have an outer lipid layer called an envelope  The envelope is derived from host cell membranes  For viruses that use the plasma membrane as their envelope, the envelope is acquired as the virus exits the host cell via a process called budding  Virally encoded proteins in the envelope play a major role in the viral life cycle.  Proteins in the viral envelope are involved in attachment to host cells.  Proteins in the viral envelope mediate fusion of the virus envelope with host cell membrane during the entry of the virus into the host cell.

14. Basic Virology  Diagram of an enveloped virus (HIV):

15. Basic Virology - budding

16. Basic Virology  What is required for a virus to successfully infect and replicate in a host cell?  In order for a virus to successfully infect a host cell, the cell must contain the receptor that the virus binds to in the process of initiating an infection.  The part of the virus that binds to the receptor is called the ligand.  The ligand is on the capsid of naked viruses and on the envelope of enveloped viruses.  gp 120 (the ligand) on HIV binds to CD4 (receptor) and CXCR4 (co-receptor) on T lymphocytes or CCR5 (co- receptor) on macrophages  What is required for a virus to successfully infect and replicate in a host cell?  In order for a virus to successfully infect a host cell, the cell must contain the receptor that the virus binds to in the process of initiating an infection.  The part of the virus that binds to the receptor is called the ligand.  The ligand is on the capsid of naked viruses and on the envelope of enveloped viruses.  gp 120 (the ligand) on HIV binds to CD4 (receptor) and CXCR4 (co-receptor) on T lymphocytes or CCR5 (co- receptor) on macrophages

17. Basic Virology

18.  In order for a virus to successfully replicate in a host cell, the host cell must not only contain the receptor for the virus, it must also have the cellular machinery that the virus needs for replication.  The host range of a virus is the spectrum of host cells that the virus can successfully infect and replicate in.  If the virus successfully replicates in the host cell, the infection is productive and the host cell is said to be permissive for the virus.  In order for a virus to successfully replicate in a host cell, the host cell must not only contain the receptor for the virus, it must also have the cellular machinery that the virus needs for replication.  The host range of a virus is the spectrum of host cells that the virus can successfully infect and replicate in.  If the virus successfully replicates in the host cell, the infection is productive and the host cell is said to be permissive for the virus.

19. Basic Virology  If the cell lacks something required for viral replication, the infection is abortive or non- productive and the host cell is considered to be non-permissive for the virus.  What are the basic features of the viral life cycle?  Attachment or adsorption– ligand on virus binds to a receptor on a host cell  Penetration – virus gets inside the host cell  Penetration of naked viruses usually involves either:  Receptor mediated endocytosis or  Formation of a pore in the host cell plasma membrane through which the nucleic acid and possibly associated viral proteins enter the cytoplasm  If the cell lacks something required for viral replication, the infection is abortive or non- productive and the host cell is considered to be non-permissive for the virus.  What are the basic features of the viral life cycle?  Attachment or adsorption– ligand on virus binds to a receptor on a host cell  Penetration – virus gets inside the host cell  Penetration of naked viruses usually involves either:  Receptor mediated endocytosis or  Formation of a pore in the host cell plasma membrane through which the nucleic acid and possibly associated viral proteins enter the cytoplasm

20. Basic Virology  Penetration of enveloped viruses occurs through a fusion event between the viral envelope and a host cell membrane.  Uncoating – separation of capsid and nucleic acid in preparation of viral transcription and nucleic acid replication (attachment and penetration may occur simultaneously)  Penetration of enveloped viruses occurs through a fusion event between the viral envelope and a host cell membrane.  Uncoating – separation of capsid and nucleic acid in preparation of viral transcription and nucleic acid replication (attachment and penetration may occur simultaneously)

21. Basic Virology  Biosynthesis – viral proteins are made and viral nucleic acid is replicated  RNA viruses must bring in their own enzyme(s) for transcribing their mRNAs and replicating their genome.  This is because neither prokaryotic cells nor eukaryotic cells contain enzymes that can use RNA as a template to make a complementary copy of RNA.  Therefore, most RNA viruses replicate entirely within the cytoplasm.  Biosynthesis – viral proteins are made and viral nucleic acid is replicated  RNA viruses must bring in their own enzyme(s) for transcribing their mRNAs and replicating their genome.  This is because neither prokaryotic cells nor eukaryotic cells contain enzymes that can use RNA as a template to make a complementary copy of RNA.  Therefore, most RNA viruses replicate entirely within the cytoplasm.

22. Basic Virology  DNA containing viruses can either use the host enzymes to transcribe their mRNAs and replicate their genomes, or they may bring in their own enzymes for these processes  Retroviruses are unique RNA viruses in that they bring in an enzyme called reverse transcriptase (RT).  RT makes a double stranded DNA copy of the viral RNA genome.  This DNA then moves to the nucleus where it is incorporated into the DNA of the host cell.  It is only after this occurs that the viral genes are transcribed and translated into protein products.  DNA containing viruses can either use the host enzymes to transcribe their mRNAs and replicate their genomes, or they may bring in their own enzymes for these processes  Retroviruses are unique RNA viruses in that they bring in an enzyme called reverse transcriptase (RT).  RT makes a double stranded DNA copy of the viral RNA genome.  This DNA then moves to the nucleus where it is incorporated into the DNA of the host cell.  It is only after this occurs that the viral genes are transcribed and translated into protein products.

23. Basic Virology  Assembly or maturation – All of the viral components assemble into new viruses.  This does not occur until a sufficient number of viral proteins are made and viral genomes are replicated  Release – newly made viruses exit the host by lysis or budding  Assembly or maturation – All of the viral components assemble into new viruses.  This does not occur until a sufficient number of viral proteins are made and viral genomes are replicated  Release – newly made viruses exit the host by lysis or budding

24. Basic Virology

25.  How are viruses classified?  The most commonly used classification scheme is the Baltimore scheme.  This scheme is based on the relationship between the viral genome and the mRNA used for translation during expression of the viral genome:  How are viruses classified?  The most commonly used classification scheme is the Baltimore scheme.  This scheme is based on the relationship between the viral genome and the mRNA used for translation during expression of the viral genome:

26. Baltimore Classification of Viruses

27. Basic Virology  Effects of the virus on the host cell – even though you can’t see the virus, you can see the effects that the virus has on the host cell  Death of the cell – often occurs on release of the virus  Cytopathic effects – are visible effects on the host cell caused by viral replication  Cancer  Requires that the virus integrates all or part of its genome into the host cell DNA  Effects of the virus on the host cell – even though you can’t see the virus, you can see the effects that the virus has on the host cell  Death of the cell – often occurs on release of the virus  Cytopathic effects – are visible effects on the host cell caused by viral replication  Cancer  Requires that the virus integrates all or part of its genome into the host cell DNA

28. Overview of viral infections  Viral diseases of the skin  Warts  Caused by human papilloma virus (double stranded DNA)  Spread by direct contact  Treated with acids or cryotherapy  Smallpox (variola)  Caused by variola major (mortality >20%) and minor (mortality < 1%) (double stranded DNA)  Transmitted by respiratory route  Virus moves from respiratory tract to the bloodstream to the skin to cause a pustular rash  Leaves disfiguring scars  Viral diseases of the skin  Warts  Caused by human papilloma virus (double stranded DNA)  Spread by direct contact  Treated with acids or cryotherapy  Smallpox (variola)  Caused by variola major (mortality >20%) and minor (mortality < 1%) (double stranded DNA)  Transmitted by respiratory route  Virus moves from respiratory tract to the bloodstream to the skin to cause a pustular rash  Leaves disfiguring scars

29. Smallpox lesions

30. Overview of viral infections  Other symptoms include fever, malaise, severe backache and abdominal pain  Vaccination has successfully eradicated this disease  Problem – use in bioterrorism  Chickenpox and shingles  Caused by varicella-zoster (a herpes virus - double stranded DNA)  Infection is through the respiratory route  Incubation is ~ 2 weeks, but the infected individual is contagious at this stage  Virus localizes in the skin to cause a vesicular rash with vesicles that fill with pus, rupture, and form scabs  After chickenpox the virus remains latent in nerve cells and can be reactivated later in life to cause shingles  Other symptoms include fever, malaise, severe backache and abdominal pain  Vaccination has successfully eradicated this disease  Problem – use in bioterrorism  Chickenpox and shingles  Caused by varicella-zoster (a herpes virus - double stranded DNA)  Infection is through the respiratory route  Incubation is ~ 2 weeks, but the infected individual is contagious at this stage  Virus localizes in the skin to cause a vesicular rash with vesicles that fill with pus, rupture, and form scabs  After chickenpox the virus remains latent in nerve cells and can be reactivated later in life to cause shingles

31. Overview of viral infections  Shingles is characterized by severe pain due to inflammation of the nerve branches of the cutaneous sensory nerves around one side of the trunk.  A vaccine to prevent chickenpox is now available  Shingles is characterized by severe pain due to inflammation of the nerve branches of the cutaneous sensory nerves around one side of the trunk.  A vaccine to prevent chickenpox is now available

32. Chicken pox and shingles

33. Overview of viral infections  Measles (rubeola)  Caused by a paramyxovirus (single stranded – sense RNA)  Is highly contagious  Spread by the respiratory route  Incubation 10-12 days  Symptoms are similar to the common cold plus a papular rash (small, raised spots)  Koplik spots (red patches with central white specks) in the oral cavity are diagnostic  Measles (rubeola)  Caused by a paramyxovirus (single stranded – sense RNA)  Is highly contagious  Spread by the respiratory route  Incubation 10-12 days  Symptoms are similar to the common cold plus a papular rash (small, raised spots)  Koplik spots (red patches with central white specks) in the oral cavity are diagnostic

34. Overview of viral infections  Severe complications include encephalitis, pneumonia, ear infections, and even death  May later cause subacute sclerosing panencephalitis with progressive nerve destruction and death  A vaccine is available (part of the MMR – Measles, Mumps, and Rubella)  We should be able to eradicate this virus since man is the only known host  Severe complications include encephalitis, pneumonia, ear infections, and even death  May later cause subacute sclerosing panencephalitis with progressive nerve destruction and death  A vaccine is available (part of the MMR – Measles, Mumps, and Rubella)  We should be able to eradicate this virus since man is the only known host

35. Measles (rubeola)

36. Overview of viral infections  German measles (rubella)  Caused by a togavirus (single stranded + sense RNA)  Transmitted via the respiratory route  Symptoms include a slight fever and a rash of small red spots.  Infection during the first trimester of pregnancy can lead to birth defects (deafness, eye cataracts, heart defects, mental retardation) or death of the fetus  Vaccination via MMR  German measles (rubella)  Caused by a togavirus (single stranded + sense RNA)  Transmitted via the respiratory route  Symptoms include a slight fever and a rash of small red spots.  Infection during the first trimester of pregnancy can lead to birth defects (deafness, eye cataracts, heart defects, mental retardation) or death of the fetus  Vaccination via MMR

37. German measles (rubella)

38. Overview of viral infections  Cold sores  Caused by herpes simplex virus (HSV), type I (double stranded DNA)  Characterized by lesions of the oral mucous membranes  Following the initial infection, the virus may remain latent in the nerves  Physical or emotional stress may cause a reactivation of the latent infection  Viral diseases of the eye  Corneal lesions caused by HSV, type I can lead to blindness or CNS invasion  Cold sores  Caused by herpes simplex virus (HSV), type I (double stranded DNA)  Characterized by lesions of the oral mucous membranes  Following the initial infection, the virus may remain latent in the nerves  Physical or emotional stress may cause a reactivation of the latent infection  Viral diseases of the eye  Corneal lesions caused by HSV, type I can lead to blindness or CNS invasion

39. HSV I infections

40. Overview of viral infections  Viral diseases of the respiratory tract  The common cold  Caused mainly by rhinoviruses (single stranded + sense RNA) and coronaviruses (single stranded + sense RNA)  >200 different types of viruses can cause the common cold!  Spread by respiratory secretions on the hands  Symptoms include sneezing, nasal discharge, and congestion  Influenza  Caused by orthomyxoviruses (segmented, single stranded – sense RNA viruses)  Viral diseases of the respiratory tract  The common cold  Caused mainly by rhinoviruses (single stranded + sense RNA) and coronaviruses (single stranded + sense RNA)  >200 different types of viruses can cause the common cold!  Spread by respiratory secretions on the hands  Symptoms include sneezing, nasal discharge, and congestion  Influenza  Caused by orthomyxoviruses (segmented, single stranded – sense RNA viruses)

41. Overview of viral infections  Transmitted via respiratory secretions  Symptoms include fever, chills, headache, and general muscle aches  These organisms are continually changing their antigenic structure by shift and drift making it difficult to develop effective vaccines  Shift occurs with genetic recombination or gene reassortment  Drift occurs by mutations  Viral diseases of the central nervous system  Meningitis or encephalitis  Transmitted via respiratory secretions  Symptoms include fever, chills, headache, and general muscle aches  These organisms are continually changing their antigenic structure by shift and drift making it difficult to develop effective vaccines  Shift occurs with genetic recombination or gene reassortment  Drift occurs by mutations  Viral diseases of the central nervous system  Meningitis or encephalitis

42. Overview of viral infections  These are infections of the membranes that cover the brain and spinal cord or of the brain itself  Many different viruses can cause meningitis and encephalitis  Organisms that enter through the blood need to cross the blood-brain barrier to cause disease.  Other organisms move along peripheral nerves to the CNS  Viral meningitis is often called aseptic meningitis because no bacteria or fungi can be cultivated from the CSF  These are infections of the membranes that cover the brain and spinal cord or of the brain itself  Many different viruses can cause meningitis and encephalitis  Organisms that enter through the blood need to cross the blood-brain barrier to cause disease.  Other organisms move along peripheral nerves to the CNS  Viral meningitis is often called aseptic meningitis because no bacteria or fungi can be cultivated from the CSF

43. Overview of viral infections  Poliomyelitis (polio)  Caused by a picornavirus (small single stranded+ sense RNA)  There are three different serotypes of poliovirus  Transmission occurs via the gastrointestinal tract after ingestion of fecal contaminated water  Symptoms include fever, sore throat, and headache  In 1-2% of the cases (mainly in adults) the virus penetrates the capillary walls and enters the CNS where it it multiplies in the motor nerve cells eventually killing them and causing paralysis  Two vaccines have been used  Salk – virus inactivated by formalin  Poliomyelitis (polio)  Caused by a picornavirus (small single stranded+ sense RNA)  There are three different serotypes of poliovirus  Transmission occurs via the gastrointestinal tract after ingestion of fecal contaminated water  Symptoms include fever, sore throat, and headache  In 1-2% of the cases (mainly in adults) the virus penetrates the capillary walls and enters the CNS where it it multiplies in the motor nerve cells eventually killing them and causing paralysis  Two vaccines have been used  Salk – virus inactivated by formalin

44. Overview of viral infections  Sabin – live, attenuated virus ( recently reactivation problems have resulted in the discontinuation of the use of this vaccine)  Rabies  Caused by a bullet-shaped rhabdovirus (single stranded – sense RNA)  Transmission is via the saliva of a rabid (rabies infected) animal  Virus travels along the peripheral nerves to the CNS where it causes encephalitis  Symptoms include painful spasms of the muscles of the mouth and pharynx when swallowing liquids (hydrophobia)  Treatment is with rabies immune globulin followed by active immunization  Sabin – live, attenuated virus ( recently reactivation problems have resulted in the discontinuation of the use of this vaccine)  Rabies  Caused by a bullet-shaped rhabdovirus (single stranded – sense RNA)  Transmission is via the saliva of a rabid (rabies infected) animal  Virus travels along the peripheral nerves to the CNS where it causes encephalitis  Symptoms include painful spasms of the muscles of the mouth and pharynx when swallowing liquids (hydrophobia)  Treatment is with rabies immune globulin followed by active immunization

45. Rabies

46. Overview of viral infections  Viral diseases of the cardiovascular system  Myocarditis – inflammation of the heart muscle  Caused by many different organisms, but is commonly caused by Coxsackieviruses (single stranded + sense RNA)  Infection occurs via the respiratory route or via the gastrointestinal tract  The organism gains access to the heart via the bloodstream or the lymphatics  Viral diseases of the cardiovascular system  Myocarditis – inflammation of the heart muscle  Caused by many different organisms, but is commonly caused by Coxsackieviruses (single stranded + sense RNA)  Infection occurs via the respiratory route or via the gastrointestinal tract  The organism gains access to the heart via the bloodstream or the lymphatics

47. Overview of viral infections  Infectious mononucleosis  Caused by Epstein-Barr virus (a herpes virus – double stranded DNA)  Transmission is via saliva and hence the disease is often called the kissing disease  Symptoms include fever, sore throat, swollen lymph nodes, and general weakness  Like all herpes virus infections, after the primary infection the virus remains latent, this time in B lymphocytes  Infectious mononucleosis  Caused by Epstein-Barr virus (a herpes virus – double stranded DNA)  Transmission is via saliva and hence the disease is often called the kissing disease  Symptoms include fever, sore throat, swollen lymph nodes, and general weakness  Like all herpes virus infections, after the primary infection the virus remains latent, this time in B lymphocytes

48. Overview of viral infections  The virus has been linked to three human cancers  Hodgkins disease  Burkit’s lymphoma  Nasopharyngeal carcinoma  The virus has been linked to three human cancers  Hodgkins disease  Burkit’s lymphoma  Nasopharyngeal carcinoma

49. Burkitt’s lymphoma

50. Overview of viral infections  Viral hemorrhagic fevers  Caused by several different types of virus  Ebola virus causes this type of disease  Are transmitted from human to human  Have a high mortality rate from hemorrhaging and shock  Viral hemorrhagic fevers  Caused by several different types of virus  Ebola virus causes this type of disease  Are transmitted from human to human  Have a high mortality rate from hemorrhaging and shock

51. Ebola hemorrhagic fever

52. Overview of viral infections  Viral disease of the digestive system  Mumps  Caused by a paramyxovirus (single stranded – sense RNA)  Transmission is via salivary secretions and portal of entry is the respiratory tract  Incubation is 16-18 days – during this time the virus moves from the respiratory tract to the bloodstream to the parotid (salivary) glands and testes in males  Symptoms include swelling, fever, painful swallowing and occasionally sterility.  Vaccination is via the MMR  Viral disease of the digestive system  Mumps  Caused by a paramyxovirus (single stranded – sense RNA)  Transmission is via salivary secretions and portal of entry is the respiratory tract  Incubation is 16-18 days – during this time the virus moves from the respiratory tract to the bloodstream to the parotid (salivary) glands and testes in males  Symptoms include swelling, fever, painful swallowing and occasionally sterility.  Vaccination is via the MMR

53. Mumps

54. Overview of viral infections  Hepatitis – an inflammation of the liver  Hepatitis A (single stranded + sense RNA)  Causes infectious hepatitis  Is transmitted via the fecal-oral route  Symptoms include anorexia, malaise, nausea, diarrhea, abdominal discomfort, fever and chills for 2-21 days  2/3 of infected individuals have jaundice which is indicative of liver damage   Hepatitis – an inflammation of the liver  Hepatitis A (single stranded + sense RNA)  Causes infectious hepatitis  Is transmitted via the fecal-oral route  Symptoms include anorexia, malaise, nausea, diarrhea, abdominal discomfort, fever and chills for 2-21 days  2/3 of infected individuals have jaundice which is indicative of liver damage 

55. Overview of viral infections  Hepatitis B (double stranded DNA virus)  Causes serum hepatitis  Is transmitted through the blood  Incubation is 4-26 weeks  Symptoms range from subclinical to severe fever and headache with jaundice  90% recover completely and 10% become chronic carriers and have a high incidence of liver disease including hepatoma  A vaccine is available  Hepatitis C (single stranded RNA virus)  Causes serum hepatitis  Is transmitted through blood  The disease is clinically similar to that of hepatitis B  Hepatitis B (double stranded DNA virus)  Causes serum hepatitis  Is transmitted through the blood  Incubation is 4-26 weeks  Symptoms range from subclinical to severe fever and headache with jaundice  90% recover completely and 10% become chronic carriers and have a high incidence of liver disease including hepatoma  A vaccine is available  Hepatitis C (single stranded RNA virus)  Causes serum hepatitis  Is transmitted through blood  The disease is clinically similar to that of hepatitis B

56. Overview of viral infections  Viral gastroenteritis  In children is most commonly caused by rotavirus (double stranded RNA) or adenoviruses (double stranded DNA)  Symptoms include fever, diarrhea, and vomiting  Viral diseases of the reproductive system  Genital herpes  Viral gastroenteritis  In children is most commonly caused by rotavirus (double stranded RNA) or adenoviruses (double stranded DNA)  Symptoms include fever, diarrhea, and vomiting  Viral diseases of the reproductive system  Genital herpes

57. Overview of viral infections  Caused by herpes simplex virus (HSV), type II (double stranded DNA)  Incubation is ~ 1 week  Symptoms include painful vesicular lesions containing infectious fluid.  This virus also becomes latent in nerve cells and can be reactivated to cause the same type of lesions found in the primary infection  This virus can cross the placenta to infect the fetus leading to mental retardation and defective sight and hearing  The fetus can also be infected during the delivery, therefore all women positive for this virus routinely deliver their babies by a C- section  Caused by herpes simplex virus (HSV), type II (double stranded DNA)  Incubation is ~ 1 week  Symptoms include painful vesicular lesions containing infectious fluid.  This virus also becomes latent in nerve cells and can be reactivated to cause the same type of lesions found in the primary infection  This virus can cross the placenta to infect the fetus leading to mental retardation and defective sight and hearing  The fetus can also be infected during the delivery, therefore all women positive for this virus routinely deliver their babies by a C- section

58. HSV II infection

59. Overview of viral infections  Genital warts  Caused by human papilloma viruses (double stranded DNA viruses)  Some strains of these viruses can cause cervical cancer  There is now a vaccine for the strains associated with cervical cancer.  Genital warts  Caused by human papilloma viruses (double stranded DNA viruses)  Some strains of these viruses can cause cervical cancer  There is now a vaccine for the strains associated with cervical cancer.

60. Genital warts

61. Overview of viral infections  Prions  Cause diseases that were formerly called slow viral infections  Prions are not viruses; they have no nucleic acid associated with them  Prions are infectious proteins  They cause a misfolding of a normal cellular protein counterpart  They cause neurological diseases characterized by a spongiform encephalopathy that results in eventual death  Examples include:  Prions  Cause diseases that were formerly called slow viral infections  Prions are not viruses; they have no nucleic acid associated with them  Prions are infectious proteins  They cause a misfolding of a normal cellular protein counterpart  They cause neurological diseases characterized by a spongiform encephalopathy that results in eventual death  Examples include:

62. Overview of viral infections  Kuru  Creutzfeldt-Jakob disease  Mad cow disease  Kuru  Creutzfeldt-Jakob disease  Mad cow disease

63. Prion diseases